Shear Load Transfer Characteristics of Drilled Shafts Socketed in Rocks

ORIGINAL PAPER

Shear Load Transfer Characteristics of Drilled Shafts Socketed in Rocks

Sangseom Jeong ?Sangyong Ahn ?Hoonil Seol

Received:19December 2007/Accepted:12December 2008/Published online:3February 2009óSpringer-Verlag 2009

Abstract This paper presents a shear load transfer func-tion and an analytical method for estimating the load transfer characteristics of rock-socketed drilled shafts sub-jected to axial loads.A shear load transfer (f–w )function of rock-socketed drilled shafts is proposed based on the con-stant normal stiffness (CNS)direct shear tests.It is presented in terms of the borehole roughness and the geo-logical strength index (GSI)so that the structural discontinuities and the surface conditions of the rock mass can be considered.An analytical method that takes into account the coupled soil resistance effects is proposed using a modi?ed Mindlin’s point load solution.Through com-parisons with load test results,the proposed methodology is in good agreement with the general trend observed in in situ measurements and represents an improvement in the pre-diction of the shear behavior of rock-socketed drilled shafts.Keywords Rock-socketed drilled shaft áLoad transfer function áConstant normal stiffness direct shear test áBorehole roughness áCoupled soil resistance áPile–rock interface

1Introduction

In South Korea,a number of large construction projects,such as land reclamation for an international airport,high-speed railways,and harbor construction,are in progress in urban and coastal areas.Drilled shafts are frequently used in those areas as a viable replacement for driven piles for two applications:deepwater offshore foundations and foundations in urban areas where noise and vibration are not tolerated.Over 90%of the drilled shafts constructed in South Korea are embedded in weathered or soft rocks.Rock-socketed drilled shafts typically carry most of their working load in shaft resistance because the ultimate shaft resistance is generally mobilized at smaller interface displacements between the shaft and surrounding rock than the ultimate toe resistance.Williams et al.(1980)and Carter and Kulhawy (1988)reported that the typical range of load transmitted to the pile toe,expressed as a per-centage of the axial load applied at the pile head,is 10–20%at typical working loads.

The load transfer method is widely used to predict the load transfer characteristics of piles subjected to an axial load because it has a simple analytical procedure and can be applied to any soil pro?le,which may be complex,and be a pile with a diameter that varies with depth.In this method,load transfer functions describe the relationship between the unit resistance transferred to the surrounding soil and the displacement of the pile relative to each soil layer.A few shear load transfer (f–w or t–z )functions have been proposed to analyze the load transfer of a pile sock-eted in rocks (Baguelin 1982;O’Neill and Hassan 1994).O’Neill and Hassan (1994)suggested potential f–w behavior in rock,as shown in Fig.1.If the pile–rock interface is clean,the cement paste bonds to the rock,the roughness pattern is regular,and the asperities are rigid,an f–w relation such as OABC can be obtained.In most cases,however,the interface asperity pattern is not regular.In addition,asperities are deformable,which results in ductile,progressive failure among asperities.Therefore,O’Neill

S.Jeong (&)áH.Seol

Department of Civil Engineering,Yonsei University,Seoul 120-749,Korea

e-mail:soj9081@yonsei.ac.kr

S.Ahn

Department of Railway and Mass Transit,

Daewoo Engineering,Seongnam 463-825,Korea

Rock Mech Rock Eng (2010)43:41–54DOI 10.1007/s00603-009-0026-4

and Hassan(1994)proposed a hyperbolic f–w model that describes shear load transfer behavior for most rock types, as shown in Fig.1and Eq.1:

f?

w

2:5D

m

tw

max

e1T

where w is the pile displacement,f max is the maximum unit shaft resistance,D is the pile diameter,and E m is the effective Young’s modulus of the rock mass.

However,these f–w models are only reliable if site-speci?c correlations are developed.Even so,their reli-ability may be questionable,because they exclude many variables that affect the shaft resistance of rock sockets (Johnston1994;Kim et al.1999;Seol2007).

The important role of soil–pile interaction in the anal-ysis and design of foundations has long been recognized by geotechnical engineers.The load transfer method models the pile as a series of discrete elements,and the relationship between pile displacement and soil resistance is repre-sented by independent springs.As a result,the continuity of soil mass is not properly taken into account,and,hence, the coupled soil resistance,in which the response at any point on the interface affects other points,is neglected.

This paper is intended to evaluate the load transfer characteristics of drilled shafts installed in rocks.The f–w function is proposed to take into account various factors that in?uence the shaft resistance mechanism,such as pile and rock properties,pile–soil interface geometry and slip char-acteristics,and the type and amount of rock weathering.The validity of this study was tested through?eld case studies. 2Constant Normal Stiffness Direct Shear Test

Arti?cially made pile–rock interfaces with a series of regular sawtooth asperities were tested to analyze the basic mechanism and the effect of in?uential factors such as roughness,normal stiffness,initial normal stress,and uncon?ned compressive strength(UCS).The mechanisms established from constant normal stiffness(CNS)direct shear tests were applied to predict the performance of the shear load transfer of rock-socketed drilled shafts.

2.1Quanti?cation of Borehole Roughness

Before performing a CNS test,a quantitative analysis of borehole roughness should be carried out to determine the objective roughness represented as a natural irregular pro?le of the borehole surface.Seidel and Haber?eld (1995)recommended that roughness be scale-dependent and,therefore,all roughness statistics must be accompa-nied by a measure of scale in order for them to be meaningful.This method is based on an idealized joint interface that is modeled as a series of interconnected chords with a constant length(l a),as shown in Fig.2.It is assumed that the chord angle(h)is normally distributed with mean(l h)and standard deviation(s h).Thus,the asperity heights(D r)will vary in the distribution,which can be approximated as Gaussian for reasonable socket roughness and can be represented as follows:

D r?

1

n

X n

i?1

D r i

j j?

1

n

X n

i?1

l a sin"h

e2TBased on this approach,the natural irregular pro?le of a borehole can be simpli?ed to a regular sawtooth pattern.It is critical to note that D r depends on l a,and,thus,l a should be determined on the basis of the converged value of D r.

The quanti?ed values of roughness determined in pre-vious studies and this study are summarized in Table1. Seidel and Collingwood(2001)present bounds of rough-ness height as a function of the UCS of intact rock based on back-analysis of the existing load tests.Nam(2004)eval-uated the borehole roughness,which is constructed separately with an auger and core barrel,of four sites in clayshale and limestone using a chord length l a of50mm. Lee et al.(2003)measured the borehole roughness of granite,gneiss,sandstone,and andesite at ten different sites (15boreholes)in Korean peninsula.They report that the representative chord length of borehole roughness in gneiss–granite is approximately50mm and the roughness height D r ranges from1to5.1mm,regardless of the rock type.These ranges include the measured roughness heights

42S.Jeong et al.

(1–7mm)of two test sites in this study.Based on the results,the borehole roughness of a rock socket can be represented by a regular sawtooth roughness with a chord length l a of50mm and roughness heights D r from1to 16.2mm,which correspond to roughness angles i that range from1.1to18.9°.

2.2Sample Preparation and Testing Apparatus

Natural rock blocks with quanti?ed sawtooth roughness are required for CNS tests.It is impossible to perform a large number of CNS tests under various boundary conditions because it is dif?cult to prepare large rock block samples and to make regular asperity patterns with rock blocks that include discontinuities.Therefore,two industrial gypsum plasters were used to make an idealized sawtooth rock sample.They can be molded into any shape when mixed with water,and the long-term strength is independent of time once the chemical hydration is complete.To prepare the pile sample,cement mortar,which consists of cement and sand,was substituted for concrete because concrete contains large aggregates which can be dif?cult to?t into laboratory-scale test samples.The property values of plaster are typical of most sedimentary rocks(Indraratna et al.1998).Table2summarizes the UCS and the Young’s modulus(E s)of the two cured plasters and cement mortar that are used in this study.

Referring to the quanti?ed borehole roughness,test samples are molded by gypsum plaster and cement mortar with asperity angles of4.6,9.1,and15.6°and a chord length of25mm,as shown in Fig.3.

To model pile–rock interfaces properly in the labora-tory,a CNS direct shear testing apparatus provides large-size samples with varying shear area,an exact measure-ment of the vertical and horizontal displacement,and accurate loading according to displacements.The main part of the CNS testing apparatus used in this study comprises normal and shear sections with servo-controlled hydraulic actuators,load cells,and LVDT transducers.The split shear boxes holding the matching half-samples of rock and concrete have maximum internal dimensions of1509 2009100mm high.

Table1Quanti?ed values of roughness for rock socket(l a=50mm)

Rock type UCS

(MPa)Roughness

height(mm)

Roughness

angle(°)

Remark

This study Gneiss5–501–7 1.1–8.0Bit

Seidel and Collingwood(2001)Claystone,sandstone,

shale,limestone,etc.5–10 1.7–16.2 1.9–18.9Back-analysis 10–700.9–6.6 1.0–7.6

Lee et al.(2003)Granite100–1501–5.1 1.1–5.9RCD/all casing

Gneiss30–1301–4 1.1–4.6

Sandstone75–77

Andesite741–3.5 1.1–4.0

Nam(2004)Clayshale1–4 3.6–5.3 4.1–6.1Auger

4.7–

5.8 5.4–

6.7Core barrel

Limestone10 3.2–3.7 3.7–4.2Auger

4.3–

5.1 4.9–5.8Core barrel

Table2Material properties of constant normal stiffness(CNS) direct shear test samples

Parameters Arti?cial rock A Arti?cial rock B Drilled shaft

Material type Gypsum plaster Gypsum plaster Cement mortar UCS(MPa)203542

E s(MPa)2,7203,550–

Shear Load Transfer Characteristics43

2.3Test Conditions and Procedure

To study the in?uential factors of shaft resistance of rock-socketed drilled shafts,the CNS direct shear tests were conducted on sawtooth samples under various normal stiffnesses and initial normal stresses.A summary of the test boundary conditions is given in Table3.The normal stiffness K n of a rock-socketed drilled shaft can be deter-mined conventionally using the theoretical analysis of an expanding in?nite cylindrical cavity in an elastic half-space (Boresi1965)as follows:

K n?D r n

D r

?

E m

r1tv m

eT

e3T

where D r n is the increased normal stress,D r is the dilation, r is the radius of a pile,and E m and m m are the deformation modulus and Poisson’s ratio of the rock mass,respectively. The normal stiffness used in this study varied from0.2to 1.0MPa/mm based on back-calculation using the general properties of the rock-socketed pile.

The initial normal stress(r n0)is imposed on the side wall of a rock socket by a head of wet concrete and depends on complex in?uential factors,such as the cast velocity of concrete,the arching effect of aggregates,the hardening rate,the degree of compaction,and the shrink-age rate of cement(Taylor1965).Since it is dif?cult to conveniently incorporate all of these factors,the initial normal stress can simply be assumed to be a function of the cast depth of the concrete based on the theory of?uid static mechanics.

2.4Test Results and Discussion

A total of54individual tests were conducted under the various boundary conditions described in the previous sections(Table3).Based on the results of the CNS tests, the shear behavior of regular sawtooth rock joints under CNS conditions could be classi?ed as:(1)elastic(SP1),a non-slipping or sticking state in which normal stress is constant due to no dilation before a slip at the joint inter-face;(2)elasto-plastic(SP2),the slipping state in which dilation of the joint interface occurs during shearing and causes an additional normal stress and shear stress;(3) plastic(SP3),the residual state in which the normal and shear stress are maintained or reduced due to rupture of the asperities.In this paper,only some typical CNS test results are presented.

Figure4shows the results from three typical tests on arti?cial rock sample A with different roughness angles (4.6,9.1,and15.6°)under the conditions of0.5MPa/mm normal stiffness and0.35MPa initial normal stress.More speci?cally,the following quantities are plotted:shear stress–shear displacement(s–w),normal displacement–shear displacement(w–w),shear stress–normal stress (s–r n),and normal displacement–normal stress(w–r n).As the roughness angle i increases,the amount of normal displacement increases in the elasto-plastic portion(SP2), as shown in the normal displacement–shear displacement (w–w)curves of Fig.4a,thus,the normal stress increases

Table3Summary of the test boundary conditions

Variable Values

Roughness angle,i(°) 4.6,9.1,15.6 Normal stiffness,K n(MPa/mm)0.2,0.5,1.0 Initial normal stress,r n0(MPa)0.35,0.70,1.05

44S.Jeong et al.

as illustrated in the normal displacement–normal stress (w–r n)curves of Fig.4b.Consequently,the increased normal stress induces increased shear stress proportion-ately,as shown in the shear stress–normal stress(s–r n) curves of Fig.4b.

These results are similar to those for a roughness angle of9.1°under the same initial normal stress(0.35MPa) with three normal stiffnesses(0.2,0.5,and1.0MPa/mm), as shown in Fig.5.The peak shear stress tends to increase as the normal stiffness increases.This is explained by the fact that the normal stress tends to be increased by an increase in normal stiffness,even if both samples have the same roughness.However,while the slopes of shear stress versus normal stress curves are the same regardless of normal stiffness,they differ slightly with different rough-ness angles.

Figure6shows the shear responses under the condition of0.5MPa/mm normal stiffness and three different initial normal stresses(0.35,0.70,and1.05MPa)with a rough-ness angle of4.6°.The results demonstrate that the peak shear stress tends to increase with the initial normal stress as well as the roughness angle,and normal stiffness also increases.However,the initial normal stress has an effect on the shear stiffness and strength of SP1only before slipping occurs.In addition,the initial peak strengths of CNS tests are smaller than those of a natural rock-socketed pile because the samples of rock and concrete are molded separately,so no bonding exists between them.Once

Shear Load Transfer Characteristics45

slippage occurs,however,cohesion at the interface disap-pears so that the bonding effects may be ignored.

3Proposed Shear Load Transfer Function

Based on the CNS tests,the shear stiffness of the elastic portion(SP1)depends on the initial normal stress,while that of the elasto-plastic portion(SP2)depends on both rock socket roughness and normal stiffness.It has also been known that a reduction in joint shear strength is in?uenced by the rock mass characteristics,such as rock type,joint structure,and weathering of the joint wall.To consider the various factors of shear behavior at the pile–rock interface, a new method for the shear load transfer function of rock-socketed drilled shafts is proposed based on the Hoek–Brown failure criterion.

The mechanical behavior of a pile–rock interface is a speci?c case of the mechanical behavior of all problems involving rock–rock joints.A signi?cant amount of research on the shear behavior of pile–rock interfaces has been carried out extensively and diversely from the research of rock–rock joints(Ooi1989;Seidel and Haber?eld1995;Indraratna et al.1998).The criterion of Hoek and Brown(1997),which is based on the assessment of interlocking rock blocks and the condition of the sur-faces between these blocks,is de?ned as follows:

r0 1?r03tr ci m b

r0

3

r ci

ts

a

e4T

where r01and r03are the major and minor effective principal stresses at failure,respectively,r ci is the UCS of an intact rock,m b is the reduced value of the material constant m i for a rock mass,and s and a are the constants that depend on the rock mass characteristics.Equation4, which is expressed in terms of the major and minor principal stresses,can be rewritten as a nonlinear relationship(see Fig.7a)between shear and normal stresses as follows(Hoek and Brown1997):s?A r ci

r0

n

àr tm

r ci

B

e5T

where s is the shear strength for which the unit shaft resistance f can be substituted,A and B are regression constants,r0n is the effective normal stress,and r tm is the tensile strength of the rock mass,which is s r ci/m b.

Once this envelope(Eq.5)is transferred in relation to shear stress and shear displacement,the shear load transfer function of the rock-socketed pile can be expressed as a nonlinear triple curve,consisting of three parts as shown in Fig.7b:a linear pre-slip portion(SP1),a nonlinear slip portion(SP2),and a post-slip portion(SP3).

The normal stress r0n can be obtained by summing up the initial normal stress r n0and increments of normal stress D r n as follows:

r0

n

?r n0tD r n?r n0tK n wàw st

eTtan ie6T

where r n0is a function of the cast depth z of the concrete based on the theory of static?uid mechanics and D r n is obtained from the product of the normal stiffness K n and normal displacement w,which is calculated in turn from the relative displacement of the pile–rock interface and asperity angle.

The normal stiffness can be determined conveniently from Eq.3.The relative displacement of the pile–rock interface is calculated by subtracting the current displace-ment w and maximum displacement w st of the elastic portion(SP1).The maximum displacement is closely related to the rock mass modulus and geological conditions (O’Neill and Hassan1994).In addition,based on the results of both CNS tests and?eld load tests,w st lies in the range between0.5and2mm and the initial slope of f–w relations of rock-socketed drilled shafts decreases as the degree of weathering increases(Seol and Jeong2007).This range is in general agreement with the observations of Kim et al.(1999).Therefore,w st can be conveniently proposed to be the following linear function of GSI:

w st?2à1:5GSI=100mm

eT:e7T

46S.Jeong et al.

When compared with measured and predicted normal displacement w,the elastic deformation of asperity reduces the dilation component and produces a dilation angle less than the initial asperity angle.However,the results of regression analysis using the results of CNS tests and?eld pile load tests show that the present method is not particularly sensitive to the elastic deformation of asperity at the pile–rock interface.Consequently,the shear transfer function,considering the in?uential factors of the shaft resistance of rock-socketed drilled shafts,is proposed as the following nonlinear triple curve comprising SP1,SP2,and SP3:

f?A r ci

r n0ààs r ci

m b

r ci

2

4

3

5

B

?

w

w st

for w w st

eTe8aT

f?A r ci

r n0tK n tan i wàw st

eT

? ààs r ci

m b

r ci

2

4

3

5

B

for w st\w w max

eT

e8bTf?f max for w max\w

eTe8cTwhere r ci is the UCS of the weaker materials(rock or pile) and A and B are the strength parameters that depend on the GSI of the rock mass.Strength parameters A and B can be obtained using regression analysis.By normalizing and taking logarithms,Eqs.8a–8c will be a linear line with slope B and an intercept log A.

Figure8shows the variations of peak shear stress s max against normal stress in the log-transformed coordinates X and Y based on the results of the CNS tests.In Fig.8,GSI and s were set as100and1,respectively,because test samples are considered to be intact rock,and the value of m i was determined directly from rock triaxial compressive tests on the intact rock.Thus,the proposed function suit-ably represents the peak shear strength of joints,and can properly predict the shear strength of regular sawtooth joints,taking into account their roughness,normal stiff-ness,and initial normal stress.

The proposed function is validated through?eld case histories to estimate parameters A and B.To this end,a total of ten large-diameter drilled shafts socketed in rocks with various degrees of weathering are critically analyzed. The test piles under review range from0.76to3.0m in diameter and6.4to43.8m in length.Among the ten piles, six tests are examined by the Osterberg cell load testing method.Details of all the tests are given in Table4:rock type,pile length(L),pile diameter(D),elevation of esti-mated f–w curve(-E.L),UCS of intact rock(r ci),rock mass modulus(E m),rock quality designation(RQD),rock mass rating(RMR),GSI which can be correlated with RMR, roughness angle(i),ultimate unit shaft resistance(f max), material constant for the intact rock(m i),and initial normal stress(r n0).

Figure9shows the relationship between the strength parameters and GSI.The values of A are constant at about

0.23and the values of B range from0.48to0.82.Parameter

B tends to decrease logarithmically as the GSI of the rock mass increases,and can be approximated,for the sake of simplicity,with a bi-linear curve as follows:

B?à0:008GSIt0:94for GSI\45

eTe9aTB?à0:002GSIt0:67for GSI!45

eTe9bTFinally,the proposed shear transfer function of drilled shafts socketed in rocks can be obtained by substituting A and B into Eqs.8a–8c.

4Load Transfer Analysis by Coupled Soil Resistance The load transfer method models discrete elements on the pile and represents the soil as a set of load transfer curves that describe the soil resistance as a function of pile dis-placements at several discrete points along the pile, including the pile tip.It is implicit that coupled soil resistance in which the response at any point on the interface affects other points is neglected.

The authors proposed a methodology to consider this coupling effect based on a combination of the load transfer method and the elastic method using Mindlin’s equation (Kim et al.1999).They reported the solution procedure of the methodology to consider the coupling effect,which takes into account the coupled soil resistance.Here,the continuity of the soil mass was considered based on Mind-lin’s solution.The vertical displacement at any element due to shear on the other elements is introduced as follows:

Shear Load Transfer Characteristics47

w s

f g?D

E s

I s? p f ge10T

where{w s}is the vertical displacement of soil adjacent to the pile,{p}is a pile stress vector,D and E s are the pile diameter and Young’s modulus of the soil,respectively,and[I s]is the in?uence factor,which is approximately obtained by integrating Mindlin’s equation to determine the displacement due to a point load within a semi-in?nite mass.

As a result of n elements and the base,the element of in?uence factor I s can be classi?ed into two different components:one is I b j(j=1-n),which is the toe dis-placement due to shear stress on an element j,and the other is I ij(i=j),which is the vertical displacement factor for i due to shear stress on element j.Therefore,the pile toe displacement caused by the load transmitted along the pile shaft can be expressed as:

w bs?

D

E s

X n

j?1

I b j f j

àá

e11T

where f j is the shear stress on element j and I b j is the vertical displacement factor for the base due to shear stress on element j(see Fig.10):

I b j?p

Z j D L

jà1

eTD L

I p d ce12T

where the length of the element D L is L/n,c is the embedded depth to element j,and I p is the in?uence factor for vertical displacement due to a vertical point load (Poulos and Davis1968;Kim et al.1999).By substituting

Table4Material properties of test piles

Site Pile no.Rock type L(m)D(mm)-E.L(m)q u(MPa)E m(MPa)RQD RMR GSI a i(°)f max(kPa)m i c

Gyeonggi D2Gneiss(CW)13.51,00012.94890502217 4.6b[67033 D3Gneiss(CW)13.51,00012.24897402217 4.6b72033 D4Gneiss(HW)13.51,00012.1481,20393126 4.6b[1,10033 Gneiss(MW)12.9481,9324042371,600 D5Gneiss(MW)13.51,00012.9482,748524540 4.6b1,83033 Inchon W8Granite(MW)45.12,40044.5352,1308–40e 4.6b1,40033

47.9352,300–45e1,750

E7Granite(MW)402,40049.0301,48018–35e 4.6b1,40033

50.7301,93045e1,720

E5Granite(MW)40.13,00049.5541,63025–45e 4.6b2,37033

51.5541,300–40e1,950

52.5541,300–45e1,630 Houston H Clayshale(SW)3d7609.217095–95e 4.71029

D Clayshale(SW) 5.8d7607.0420082–90e 6.24059

R Limestone(SW) 4.5d760 4.01090088–95e 3.71,54510

CW=completely weathered;HW=highly weathered;MW=moderately weathered;SW=slightly weathered

a GSI=RMR

76

=RMR89-5(where,RMR76[18,RMR89[23)

b Moderate magnitude of hole roughness angle

c The value of the Hoek–Brown constant m for intact rock(after Hoek an

d Brown1997)

d Length of test socket

e General reference value presumed without performing?eld tests

48S.Jeong et al.

Eq.12into Eq.11,the pile toe displacement w bs caused by the load carried by the pile shaft can be calculated.

4.1Solution Procedure

The mechanical model of a pile under axial loading is shown in Fig.11.The pile is considered to be composed of a series of deformable springs of length D L connected by rigid joints at nodes denoted by the symbol i.The pile stiffness is modeled as a linear spring with stiffness AE/D L, where A is the cross-sectional area and E is the modulus of

elasticity.External loads Q and support springs S(shaft resistance S f–w of n?1and toe resistance S q–w of1)may be placed at each node i.The internal force in each spring is termed the thrust and is denoted by the symbol T. Displacements w are considered positive in the positive x-direction,as shown in Fig.11.Tensile thrust is consid-ered to be positive.The force–equilibrium equation for any node i can be expressed as follows:

àT itT it1tQ iàS i w iàw bs

eT?0e13Twhere w i is the total displacement at node i,w bs is the pile toe displacement caused by the load transmitted along the pile shaft(Eq.11),so that w i-w bs represents the relative displacement between the pile and soil.At node0(pile head)and node n(pile toe),half-values of the soil reaction stiffness S f–w should be used because the equivalent spring at each node represents the soil reaction stiffness for half of the layer depth,which is equal to half the length of the corresponding element.

From the force–deformation relationships for each spring,the member forces must be:T i?

AE

eT

iàw ià1tw i

eTe14aTT it1?

AE

eT

it1

D L

àw itw it1

eTe14bT

A convenient and powerful procedure for solving this problem for nonhomogeneous soil pro?les and complicated inelastic transfer functions is to formulate a full set of nonlinear equations by applying Eqs.13,14a,and14b.The nonlinear analyses were performed taking into account the coupled soil resistance effect at the pile–soil interface and were then used in iterative and incremental analysis.The incremental procedure divided the external load into many small and equal increments that were applied sequentially.

5Validation with Case Histories

The validity of the proposed methodology was tested by comparing the results from the present approach with some of the measured results in detail in the following section.

Shear Load Transfer Characteristics49

5.1Gyeonggi Case

The load transfer characteristics of three instrumented drilled shafts (D2,D4,and D5)reported by Kwon (2004)are compared with the predicted values of the proposed methodology.These piles were founded in completely to moderately weathered gneiss.Figure 12shows an ideali-zation of the subsurface pro?le and shaft embedments for the test piles (D2,D4,and D5).All of the test piles are 1,000mm in diameter and 13.8m in length.

Table 5shows the transfer functions and material properties used in this study:the UCS of an intact rock (r ci ),the soil or rock mass moduli (E s ),the unit weight (c ),the mean roughness angle (i ),the geological strength index

(GSI),the ultimate unit shaft resistance (f max ),and the critical displacement (w max )of the pile segment which occurs at f max .The properties of the material and interface for the gneiss layer were chosen based on the results of a soil investigation,but those for the ?ll and residual soil layers were assumed by using general reference values without performing ?eld tests.

The roughness in the f–w model of the gneiss layer is characterized by the chord length and the mean roughness angle,which are then used to generate fractal roughness pro?les for the socket wall,as mentioned in the previous section.The borehole roughness for rocks with UCS greater than 20MPa was represented by a regular sawtooth with a chord length of 50mm and a roughness angle ranging from 1.1to 8.0°based on the results of the bore-hole roughness pro?ling tests (Table 1).This approach yielded an average roughness angle for the test shafts of 4.6°.Also,the f max used in the interface model of the rock layer was determined by its empirical relationship with the rock mass modulus (Seol and Jeong 2007).

Figure 13shows the predicted and measured f–w curves for the test piles.The measured shaft resistance did not reach the ultimate state and continued to increase as the displacement increased.This observation agrees with the observation of Williams et al.(1980),who report that the more a rock mass is weathered,the greater the shaft displacement before the ultimate state is reached.As a result,propagation failure occurs gradually.The proposed f–w function generally does a better job of predicting the measured shaft resistance than other load transfer functions

--Gneiss [MW]Gneiss [HW]

D2

D4

D5

Fill Fill

---Gneiss [HW]Gneiss [MW]1m

1m

1m

-Subsurface shaft test Table 5Subsurface pro?le and material properties (Gyeonggi case)Pile no.

Subsurface pro?le Transfer function Material properties Type

Depth (m)q u (MPa)

E s (MPa)c (kN/m 3)i (°)GSI f max (kPa)w max (m)–Pile 0–13.8–3328,000

23.0––––D2

Shaft

Fill 0.3–10.4Bi-linear ––17.5––1000.01Residual soil 10.4–12.5Bi-linear ––18.0––3000.01Gneiss (CW)

12.5–13.8

Proposed 4890521.0 4.6a

171,290b

–Toe Gneiss (CW)–Hyperbolic c 48905–––25,000d

–D4

Shaft

Fill 0.3–11.7Bi-linear ––17.5––1000.01Gneiss (HW)11.7–12.7Proposed 481,20321.0 4.6a 261,490b –Gneiss (MW)

12.7–13.8

Proposed 481,93221.0 4.6

a 371,890

b –Toe Gneiss (MW)–Hyperboli

c c 481,932

–––25,000d

–D5

Shaft

Fill 0.3–10.6Bi-linear ––17.5––1000.01Residual soil 10.6–12.5Bi-linear ––18.0––3000.01Gneiss (MW)

12.5–13.8

Proposed 482,74821.0 4.6a 402,250

b –Toe

Gneiss (MW)–

Hyperbolic

c

48

2,748

–

–

–

25,000

d –

a Moderate magnitude of borehole roughness angle

b Predicted value by f max =0.135P a (E m /P a )0.5(Seol and Jeong 2007)

c Castelli et al.(1992)

d

Ultimate unit toe resistance (q max )

50S.Jeong et al.

(Baguelin1982;O’Neill and Hassan1994).In particular, the proposed f–w function is in reasonably good agreement with the f–w curves measured by load tests in highly weathered rock.

Figure14shows the predicted and observed load set-tlement curves for the test piles.The proposed methodology(with the proposed f–w function and soil coupling effect)accurately predicts the general trend of the measured values when compared with the results from the existing method(with only the proposed f–w function).The analysis of all test piles using the existing method has a considerably smaller settlement when compared with the results of the present solution.This clearly demonstrates that,for test piles,there exists soil coupling,which is represented by w bs,so that this set of prediction results

Shear Load Transfer Characteristics51

demonstrates the in?uence of pile–toe settlement due to the transfer of shaft shear loading.

Figure15shows the predicted and observed axial load distribution of the test piles.In Fig.15,only the results of the proposed methodology are presented;results using the existing method are excluded.This is because the force–equilibrium equations are calculated by excluding w bs,so that the axial load distributions obtained via the present approach are consistent with those of the existing method. It is observed that agreement between the measured and predicted values is generally good.

5.2Hong Kong Case

The load transfer characteristics of one instrumented dril-led shaft installed in volcanic tuff are compared with the predicted values of the proposed load transfer analysis. Figure16shows the subsurface pro?le and shaft embed-ments(Zhan and Yin2000).Test pile V2is1,050mm in diameter and35.6m in length.The bitumen coating and cement and bentonite grout sleeve on the outside of the test pile were used to minimize the friction developed along the pile shaft,thereby allowing most of the applied load at the pile head to reach the rock socket level.The soil properties and shear transfer functions were chosen to represent the soil and rock based on soil borings and pile load tests. Table6shows the transfer function and material properties.

Figures17and18show a comparison of the load set-tlement curves and axial load distributions for the test piles, respectively.The proposed methods(with the proposed f–w function and soil coupling effect)accurately predict the general trend of the measured values when the results are compared with the results produced using the existing method(with only the proposed f–w function).Most of the applied load was transferred into the rock socket nearby pile toe due to the bitumen coating and cement bentonite grout;thus,there was a considerable coupling effect caused by the load carried by the pile shaft.

1.05m

pro?le

52S.Jeong et al.

6Conclusions

The main objective of this study is to propose a practical method of rock-socketed drilled shafts that can consider various factors that in?uence shaft resistance.Through comparisons with case histories,the proposed load transfer function and analytical method are found to be in good agreement with in situ measurements.From the ?ndings of this study,the following conclusions are drawn:1.

Based on the results of constant normal stiffness (CNS)tests,the shear load transfer behavior of rock-socketed drilled shafts can be explained using three sections consisting of an elastic (SP1),elasto-plastic (SP2),and plastic portion (SP3).The shear behavior of the three portions depends largely on the in?uencing factor of shaft resistance.In addition,the peak shear strength and shear stiffness of SP1increase as the initial normal stress increases,whereas those of SP2increase as the roughness angle and normal stiffness increase.

2.

By taking into account various shaft resistance factors that are in?uential under the CNS condition,the new f–w function is appropriate and realistic for represent-ing the shear load transfer characteristics of a drilled shaft socketed in a rock mass.The physical processes modeled theoretically include slippage at the pile–rock interface and frictional–dilative shear behavior.

3.

The analysis using the present method with the coupling effect has a considerably larger settlement when compared with the results generated by the existing methods.Soil coupling does exist in the test piles and is represented by w bs .

References

Baguelin F (1982)Rules for the structural design of foundations based

on the selfboring pressuremeter test.In:Proceedings of the

Table 6Subsurface pro?le and material properties (Hong Kong case)Pile no.

Subsurface pro?le Transfer function Material properties Type Depth (m)q u (MPa)E s (MPa)c (kN/m 3)i (°)GSI f max (kPa)w max (m)–Pile

0–35.6–4541,000

23.0––––V2

Shaft Fill 0–33.6Bi-linear ––17.5––70.01Tuff (MW)33.6–35.6

Proposed 302,00021.0

4.6a 502,700b –Toe

Tuff (MW)

–

Hyperbolic c

30

2,000

–

–

–

25,000d

–

a Moderate magnitude of borehole roughness angle

b Predicted value by f max =0.135P a (E m /P a )0.5(Seol and Jeong 2007)

c Castelli et al.(1992)

d

Ultimate unit toe resistance (q max )

Shear Load Transfer Characteristics

53

Symposium on the Pressuremeter and its Marine Application, IFP,Paris,France,April1982,pp347–362

Boresi AP(1965)Elasticity in engineering mechanics.Prentice-Hall, Englewood Cliffs

Carter JP,Kulhawy FH(1988)Analysis and design of drilled shaft foundations socketed into rock.Final report,EL5918/Project 1493–4/Electric Power Research Institute.Cornell University, Ithaca

Castelli F,Maugeri M,Motta E(1992)Analisi non lineare del cedimento di un Palo Singolo.Rivista Italiana di Geotechnica 26(2):115–135

Hoek E,Brown ET(1997)Practical estimates of rock mass strength.

Int J Rock Mech Min Sci Geomech Abstr34(8):1165–1186 Indraratna B,Haque A,Aziz N(1998)Laboratory modelling of shear behaviour of soft joints under constant normal stiffness condi-tions.Geotech Geol Eng16:17–44

Johnston IW(1994)Movement of foundations on rock.Geotechnical special publication no.40.Vertical and horizontal deformations of foundations and embankments ASCE,vol2,pp1703–1717 Kim SI,Jeong SS,Cho SH,Park IJ(1999)Shear load transfer characteristics of drilled shafts in weathered rocks.J Geotech Geoenviron Eng ASCE125(11):999–1010

Kwon OS(2004)Effect of rock mass weathering on resistant behavior of drilled shaft socketed into weathered rock.PhD dissertation, Seoul University

Lee MH,Cho CH,Yoo HK,Kwon HK(2003)A study on the surface roughness of drilled shaft into rock in Korea.In:Proceedings of the Korean Geotechnical Society Conference,KGS,Seoul, pp431–438

Nam MS(2004)Improved design for drilled shafts in rock.PhD dissertation,University of Houston O’Neill MW,Hassan KM(1994)Drilled shaft:effects of construction on performance and design criteria.In:Proceedings of the International Conference on the Design and Construction of Deep Foundations,vol1,Federal Highways Administration, Washington DC,pp137–187

Ooi LH(1989)The interface behaviour of socketed piles.PhD dissertation,University of Sydney

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Seidel JP,Haber?eld CM(1995)Towards an understanding of joint roughness.Rock Mech Rock Eng J28(2):69–92

Seol HI(2007)Load transfer analysis of rock-socketed drilled shafts by considering coupled soil resistance.PhD dissertation,Yonsei University

Seol HI,Jeong SS(2007)Shaft resistance characteristics of rock-socketed drilled shafts based on pile load tests.J Korean Geotech Soc23(9):51–63

Taylor WH(1965)Concrete technology and practice,1st edn.Angus and Robertson,Sydney

Williams AF,Johnston IW,Donald IB(1980)The design of socketed piles in weak rock.In:Proceedings of the International Conference on Structural Foundations on Rock,Sydney,Aus-tralia,May1980.Balkema,pp327–347

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54S.Jeong et al.

(易错题精选)初中英语词汇辨析的单元汇编含答案解析

一、选择题 1．I’d like to________the mall because it’s crowded and noisy. A．visit B．hang out C．walk D．go off 2．That path ________ directly to my house.You won't miss it. A．leads B．forms C．repairs D．controls 3．I don’t want to go. __________, I am too tired. A．However B．And C．Besides D．But 4．Some animals carry seeds from one place to another, ________ plants can spread to new places. A．so B．or C．but D．for 5．When I as well as my cousins __________ as a volunteer in Beijing, I saw the Water Cube twice. A．were treated B．treated C．was served D．served 6．He is wearing his sunglasses to himself from the strong sunlight. A．prevent B．stop C．keep D．protect 7．When you are________, you should listen to music to cheer you up. A．shy B．afraid C．strict D．down 8．Mr. Smith gave us some________on how to improve our speaking skills. A．advice B．news C．knowledge D．information 9．World Book Day takes place ________ April 23rd every year. A．at B．in C．on 10．More and more people have realized that clear waters and green mountains are as ________ as mountain of gold and silver. A．central B．harmful C．valuable D．careful 11．We loved the food so much, ________the fish dishes. A．special B．especial C．specially D．especially 12．—Oh, my God! I have ________ five pounds after the Spring Festival. —All of the girls want to lose weight, but easier said than done. A．given up B．put on C．got on D．grown up 13．—What do you think of the performance today? —Great! ________ but a musical genius could perform so successfully. A．All B．None C．Anybody D．Everybody 14．He ________ his homework________the morning of Sunday. A．doesn’t do; on B．doesn’t do; in C．doesn’t; on 15．Maria ________ speaks Chinese because she doesn’t know much Chinese. A．seldom B．always C．often D．usually 16．In 2018, trade between China and Hungary rose by 7.5 percent, and recently on Friday companies from China and Hungary________ several cooperation (合作) agreements under the

人教版初一英语现在进行时

现在进行时 撰稿：王红艳审稿：白雪雁 【概念引入】 I. 什么是现在进行时？ 1）现在进行时表示说话时正在进行或发生的动作。 例如：I am reading a book. 我正在看书。 2）表示现阶段正在进行而说话时不一定在进行的动作。 例如：I am learning English hard these days. 这些日子我正在努力学习英语。 II. 现在进行时的标志词。 现在进行时常和now、at the moment、look、listen等连用。 【用法讲解】 I.现在进行时的结构。 现在进行时的结构是：助动词be（am，is，are）＋现在分词v-ing 现在分词的构成： 1）动词的后面直接加－ing。例如：work－working，study－studying 2）以不发音的字母e结尾的动词，先去掉字母e，再加－ing。例如：live－living 3）以重读闭音节结尾并且只有一个辅音字母的动词，先双写这个辅音字母，再加－ing。 例如：stop－stopping，swim－swimming，run－running II. 现在进行时的用法。 1）现在进行时表示说话的时候正在进行的动作，经常和now，right now，at the moment 等时间状语或者动词look，listen等连用。 例如：My father is watching TV now.我爸爸现在在看电视。 Look! My brother is playing basketball there. 看！我弟弟正在那里打篮球。 2）现在进行时可以表示目前一段时间内一直进行的动作，经常和these days，this week，at present等时间状语连用。 例如：My parents are working on a farm these days. 这些天我的父母在农场干活。 3）现在进行时还可以表示现在不断发展变化的事情，表示不断发展变化的动词有get，grow，turn，become等。 例如：The leaves are turning yellow. 树叶在变黄。 4）现在进行时还可以表示将要发生的动作，只限于动词arrive，begin，go，come，leave，fly等动词。 例如：I am coming soon. 我马上来。 Ⅲ. 现在进行时的句式变化。 肯定句式：主语+be( am, is, are)+现在分词+其它. 否定句式：主语+be(am, is, are) +not +现在分词+其它. 一般疑问句：Be(am, is, are) +主语+现在分词+其它？ 特殊疑问句：疑问词+be(am, is, are)+主语+现在分词+其它？ 对现在进行时的特殊疑问句的回答，它不可以用Yes或No直接作答，要根据实际情况回答。 Ⅳ. 现在进行时的特殊用法。 表示位置移动的动词，如：leave/ come/go/begin等用于现在进行时，表示按计划或安排近期将要进行的动作，常与表示将来的时间状语连用。 —Can you help me? 你能帮我吗？

如何安装电脑声卡驱动

如何安装电脑声卡驱动 随着操作系统安装包的不断增多，例如vista，安装包已经达到了几G，系统附带的驱动包也变的更加全面。有时候，系统安装好后，很多硬件不用安装驱动就可以正常使用了。但是并不是所有的硬件都能免安装驱动，比如有时候安装完系统后，声卡没有被成功驱动，播放器放不出声音，下面笔者就来介绍下如何安装声卡。 右键点击―我的电脑‖----―属性‖---―硬件‖----―设备管理器‖，展开―声音、视频和游戏控制器‖，看前面有没有黄色的―？‖，有，说明缺声卡驱动，没有，说明该声卡驱动不能正常使用，右击声卡，选―卸载‖将其删除，重新安装驱动。如果有声卡驱动盘，那就很简单了。将声卡的驱动光盘放入光驱，右击―声音、视频和游戏控制器‖下的？号选项，选―更新驱动程序‖，打开―硬件更新向导‖，选―是，仅这一次‖---―下一步‖---―自动安装软件‖--―下一步‖，系统即自动搜索并安装光盘中的声卡驱动程序，如果该光盘没有适合你用的声卡驱动，再换一张试试，直到完成。( 三联教程) 倘若没有声卡驱动盘，可以从网上下载相应的驱动程序。要下载相应的驱动程序，少不了要先确定声卡的型号。不知道声卡型号，看展开的―声音、视频和游戏控制器‖下的那一串字符和数字就是你的声卡型号，也可―开始‖—―运行‖—输入dxdiag, 打开―DirectX诊断工具‖—声音，从打开的界面中找。另外，如果不能查到，一般情况下，这招都不行的；可以用号称世界上最好的硬件检测工具EVEREST中文版。 下载声卡驱动的网站不少，你也可以在综合大型网站主页，把你的声卡型号输入到―搜索‖文本框中，按―搜索‖按钮，从打开的界面中，选你要下载驱动的网站。下载驱动软件要注意：一是品牌型号要对，二是在什么系统上便用，三是要看该驱动软件公布的时间，最新的未必适合使用，可多下载几个，挑着使。 下载的驱动软件一般有自动安装功能，打开后，点击即自动安装。不能自动安装的，解压后备用，要记下该软件在磁盘中的具体路径，如E：…………。右击―我的电脑‖----―属性‖---―硬件‖----―设备管理器‖，打开―声音、视频和游戏控制器‖，右击―声音、视频和游戏控制器‖ 下的？号声卡选项，选―更新驱动程序‖，打开―硬件更新向导‖，去掉―搜索可移动媒体‖前的勾，勾选―从列表或指定位置安装‖---―下一步‖，勾选―在搜索中包括这个位置‖，在下拉开列表框中填写要使用的声卡驱动文件夹的路径（E：…………---―下一步‖，系统即自动搜索并安装你指定位置中的声卡驱动程序。 安装完声卡驱动后，如果仍然没有声音，将声卡换一个插槽试试。此外还可以进我的电脑的硬件设备管理器–右击声卡—属性--资源—看有没有冲突，有进BIOS通过设置解决。 上述方法，相信对一个对驱动安装不大熟悉的朋友来说，也基本能解决声卡驱动问题了。

boring 令人厌烦的

boring 令人厌烦的，乏味的，无聊的 tedious 乏味的，单调的，冗长的 flat 单调的，沉闷的 dull 乏味的，单调的 troublesome 令人烦恼的，讨厌的，麻烦的 tired 疲劳的，累的 bored 无聊的，无趣的，烦人的 exhausted 极其疲倦的 weary 疲劳的 bright 聪敏的，机灵的 apt 聪明的，反应敏捷的 intelligent 聪明的，有才智的 shrewd 机灵的，敏锐的，精明的（表示生意上的精明） ingenious （人，头脑）灵巧的 alert 警觉的，留神的 cute 聪明伶俐的，精明的 acute/cute acute 指的是视力，感觉的敏锐 dull 愚钝的，笨的 awkward 笨拙的，不灵巧的 absurd 荒谬的 ridiculous 可笑的，荒谬的 idiotic 白痴般的 blunt 率直的，直言不讳的 clumsy 笨拙的，粗陋的 happy 快乐的，幸福的 cheerful 欢乐的，高兴的 content 满意的，满足的 merry 欢乐的，愉快的，快乐的 pleasure 高兴，愉快，满足 enjoyment 享乐，快乐，乐趣 cheer 喝彩 applause 鼓掌，掌声 optimism 乐观，乐观主义 delight 快乐，高兴 kick 极大的乐趣 paradise 天堂，乐园 instant 立即的，即刻的 instantaneous 瞬间的，即刻的 immediate 立即的，即刻的 simultaneous 同时发生的，同时存在的，同步的punctual 严守时刻的，准时的，正点的 pick 挑选，选择 select 选择，挑选 single 选出，挑出 elect 选举，推举 vote 投票，选举 appoint 任命，委派 nominate 提名，任命 propose 提名，推荐 recommend 推荐，举荐 designate 指派，委任 delegate 委派（或选举）…为代表 install(l) 使就职，任命 ballot 使投票表决 dub 把…称为 choice 选择（权） option 选择 selection 选择，挑选 alternative 取舍，供选择的东西 favorite 特别喜爱的人（或物） inclination 爱好 preference 喜爱，偏爱，优先 observe 注意到，察觉到 perceive 认识到，意识到，理解 detect 察觉，发现 appreciate （充分）意识到，领会，体会 alert 使认识到，使意识到 awake 意识到，醒，觉醒 scent 察觉 ancient 古代的，古老的 primitive 原始的 preliminary 预备的，初步的 preliminary trial初审 primary 最初的，初级的 initial 开始的，最初的 original 起初的 former 在前的，以前的 previous 先，前 prior 在前的，优先的 beforehand 预先，事先 medieval 中世纪的，中古（时代）的preceding 在先的，在前的，前面的 senior 资格较老的，地位较高的 following 接着的，下述的 attendant 伴随的 subsequent 随后的，后来的 succeeding 以后的，随后的 consequent 作为结果（或后果）的，随之发生的 resultant 作为结果的，因而发生的therefore 因此，所以 consequently 所以，因此 then 那么，因而 thus 因此，从而 hence 因此，所以 accordingly 因此，所以，于是 thereby 因此，从而

现在进行时特殊用法展现

现在进行时特殊用法展现 现在进行时表示说话时正在进行的动作，这是我们平时接触最多的。然而除此以外，现在进行时还有以下几种用法。 1．表示“在做某事的过程中”，此时动作不一定正在发生。例如： Next I'll give you a few minutes to read the article．When you are reading，make a mark where there is a new word．现在我给你们几分钟时间读一下这篇文章。在读的过程中，在有生词的地方作以标记。 2．表示按计划、方案或安排而进行的将来的动作。在这种情况下谓语动词多为非延续性动词，如come，go， leave，move，die，start，stop，arrive等，及少数延续性动词，如spend，stay等。例如： She is leaving for Guangzhou next week．她下星期就要去广州了。 We are spending the whole summer holiday inBeijing soon．不久我们要在北京度过整个暑假。 Where are you staying in Guangzhou？在广州你打算住什么地方？ 3．与副词forever，always，constantly等连用，表示赞成、厌烦、生气等情绪。例如： She is always talking loudly in our class．她总是在我们班上吵吵嚷嚷的。（表示厌烦） She's constantly changing her mind．她老是改变主意。（表示不以为然） He is forever complaining about his job．他总是对他的工作提出抱怨。（表示厌烦） 4．teach，work，live，study等表示状态的动词使用现在进行时可表状况，与一般现在时区别不大。例如： I'm studying in No．1Middle School．我在一中学习。（相当于：I study in No．1Middle School．） My brother is working in a big factory．我哥哥在一家大工厂工作。（相当于：My brother works in a big factory．） 5．表示目前经常发生的动作，然而此时动作不一定正在进行之中。例如：

boring 和bored的区别

不能片面说人做主语用ed，物做主语ing ing形式是修饰引起这种感觉的人或物；ed形式是描写人或物的感受。（当然物一般是动物） 翻译的话 ing形式的词译为“令人……的”；ed形式译为“……的” boring是令人感到厌烦的；bored是厌烦的。 a boring person 能够指一个了无情趣的人，让人觉得无趣的人 a bored person 则是说这个人自己感到很无趣 1.bore 1）vt.使厌烦；挖 e.g. I'm bored with this job. 这件工作厌烦了。 The oldier bore the sharp pain in the wound with great courage. 这士兵以巨大的勇气忍受着伤口的剧烈疼痛。 2）n.令人讨厌的人（或事） e.g. It's a bore having to go out again. 外出真是讨厌。 boredom n.厌倦，无趣 e.g. in infinite boredom 极其无趣 boring n. 钻(孔) adj. 令人厌烦的(事或物） e.g. The play was boring. 这部短剧很一点意思都没有。 bored adj. 无聊的, 无趣的, 烦人的 e.g. Jack is so bored. 杰克是个没有趣的人。 2.surprising 是针对事或物感到惊奇。 surprised 则是针对人。 3.pleasant adj. 愉快的, 快乐的, 舒适的, 合意的可爱的, 举止文雅的, 活泼的滑稽的, 有趣的 (天气)晴朗的, 美好的容易相处的, 友爱的 e.g. a pleasant voice 悦耳的声音 a pleasant companion 可爱的伴侣 a pleasant time 愉快地度过时光 pleasing adj. 舒适的, 使人愉快的; 满意的; 惹人喜欢的, 可爱的 e.g. a pleasing look 使人愉快的神情 a very well mannered and pleasing young man 彬彬有礼而令人喜爱的年轻人

现在进行时_动词加ing的变化规律

现在进行时动词加ing的变化规律 1)一般情况下，直接加 -ing: 如：go—going answer—answering study—studying be—being see—seeing [注一] 和名词复数、一般现在时动词第三人称单数加-s(-es)不同， 动词末尾如为“辅音字母 + y”时，y不变，其后直接加ing。 如: study—studying fly—flying carry—carrying [注二] 动词结尾为辅音字母r时，加-ing，r在此必须发音。 如: water—watering answer—answering wear—wearing 2)以不发音的e结尾的动词，去掉e，再加ing 如：come—coming write—writing take—taking become—becoming 3)动词是闭音节的单音节词，或是以重读闭音节结尾的多音节词， 而末尾只有一个辅音字母时，这个辅音字母须双写，然后再加ing。 如：sit—sitting run—running stop—stopping begin—beginning admit—admitting forget—forgetting [注一] send，think，accept等动词虽是闭音节或以重读闭音节结尾， 但末尾有一个以上的辅音字母，因此，这个辅音字母不双写，应直接加ing。 如：sending thinking accepting 4)少数几个以-ie结尾的动词，须将ie变作y，再加ing。 如：die—dying tie—tying lie—lying躺，说谎 5)少数以-c结尾的动词变为现在分词时和过去式，须先将-c变为ck,然后再加-ing 或-ed 。 如：picnic—picnicking (picnicked) traffic—trafficking (trafficked)

驱动程序详解及安装方法

驱动程序详解及安装方法 想要熟知驱动安装方法首先要了解电脑硬件大概信息，了解了硬件信息安装就比较简单了，下面笔者为大家详解，首先我们了解驱动为何物。 一、什么是驱动程序 根据百度百科：驱动程序，英文名为Device Driver，全称为设备驱动程序，是一种可以使计算机和设备通信的特殊程序，可以说相当于硬件的接口，操作系统只有通过这个接口，才能控制硬件设备的工作，假如某设备的驱动程序未能正确安装，便不能正常工作。因此，驱动程序被誉为硬件的灵魂、硬件的主宰、和硬件和系统之间的桥梁等。 刚安装好的系统操作系统，很可能驱动程序安装得不完整。硬件越新，这种可能性越大。菜菜熊之前看到的图标很大且颜色难看就是没有安装好驱动的原因。 二、驱动程序的作用 随着电子技术的飞速发展，电脑硬件的性能越来越强大。驱动程序是直接工作在各种硬件设备上的软件，其驱动这个名称也十分形象的指明了它的功能。正是通过驱动程序，各种硬件设备才能正常运行，达到既定的工作效果。

硬件如果缺少了驱动程序的驱动，那么本来性能非常强大的硬件就无法根据软件发出的指令进行工作，硬件就是空有一身本领都无从发挥，毫无用武之地。这时候，电脑就正如古人所说的万事俱备，只欠东风，这东风的角色就落在了驱动程序身上。如此看来，驱动程序在电脑使用上还真起着举足轻重的作用。 从理论上讲，所有的硬件设备都需要安装相应的驱动程序才能正常工作。但像CPU、内存、主板、软驱、键盘、显示器等设备却并不需要安装驱动程序也可以正常工作，而显卡、声卡、网卡等却一定要安装驱动程序，否则便无法正常工作。这是为什么呢？ 这主要是由于这些硬件对于一台个人电脑来说是必需的，所以早期的设计人员将这些硬件列为BIOS能直接支持的硬件。换句话说，上述硬件安装后就可以被BIOS和操作系统直接支持，不再需要安装驱动程序。从这个角度来说，BIOS也是一种驱动程序。但是对于其他的硬件，例如：网卡，声卡，显卡等等却必须要安装驱动程序，不然这些硬件就无法正常工作。 三、驱动程序的界定 驱动程序可以界定为官方正式版、微软WHQL认证版、第三方驱动、发烧友修改版、Beta测试版。初学者尽量安装官方正式版，当然如果你脱离了菜鸟就可以尝试下各种版本的驱动。 动手安装驱动程序之前，必须先搞清楚，哪些硬件是需要安装驱动程序的，哪些是不需要的。根据前面的介绍，CPU、内存、软驱、键盘、显示器等一般都

现在进行时用法

现在进行时 一、定义及用法： 1定义：（1）表示说话时正在进行的动作及行为。（2）表示现阶段正在进行的动作。 2基本用法： (1)现在进行时主要表示说话人的说话时刻正在进行的动作、不断重复的动作或目前这个阶段（不一定是说话时刻）正在进行的动作，如： We’re having a meeting. 我们在开会。（说话时正在进行的动作） Be quiet！The baby is sleeping.安静，孩子在睡觉。 He is teaching in a middle school. 他在一所中学教书。（目前阶段在进行的动作） (2)现在进行时表将来: 现在进行时表将来，主要表示按计划或安排要发生的动作： I’m leaving tomorrow. 我明天走。 They’re getting married next month. 他们下个月结婚。 注意：现在进行时与一般现在时均可表示将来，区别是：用现在进行时表示将来，其计划性较强，并往往暗示一种意图；而一般现在时表示将来，则其客观性较强，即通常被视为客观事实，多指按时刻表或规定要发生的情况： I’m not going out this evening. 今晚我不准备出去。 What time does the train leave？火车什么时候开？ (3)现在进行时表示感情色彩: 现在进行时有时可表示满意、称赞、惊讶、厌恶等感情色彩，通常与always，forever，constantly，continually等副词连用。比较： She’s always helping people. 她老是帮助别人。（表赞扬） She always helps others. 他总是帮助别人。（陈述一个事实） The boy is constantly lying. 这孩子老是撒谎。（表示厌恶） The boy often lies. 这孩子常撒谎。（指出缺点） 二、结构: 现在进行时常有三种句型： （1）肯定式：主语＋be＋v-ing＋其它。 如：He is mending his bike．他正在修自行车。 （2）否定式：主语＋be＋not＋v-ing＋其它。 如：He is not（isn't）mending his bike．他没在修自行车。 （3）疑问式：主要分一般疑问句和特殊疑问句两种句式。 一般疑问句：Be＋主语＋v-ing＋其它？ 如：—Is he mending his bike？他正在修自行车吗？—Yes，he is．（No，he isn't．）特殊疑问句：疑问词＋be＋主语＋v-ing＋其它？ 如：—What is he doing？他正在干什么？ 三、何时用现在进行时？ （1）以Look！或Listen！开头的句子提示我们说话时动作正在进行，应用现在进行时。 如：Look！The children are playing games over there． Listen！Who's singing in the classroom？ （2）当句子中有now（现在）时，常表示说话时动作正在进行，这时也常用现在进行时。 如：We are reading English now． （3）描述图片中的人物的动作时常用现在进行时，以示生动。 如：Look at the picture．The girl is swimming． （4）表示当前一段时间内的活动或现阶段正在进行的动作时常用现在进行时。这时常与时间状语these days，this week等连用。

如何在windows7下安装hp1020打印机驱动程序

在 Windows 7 下安装 HP1020 打印机驱动程序方法 注意事项: 电脑上曾经安装过HPLaserJet 激光打印机的驱动程序，重新安装驱动程序之前，需要先删除以前安装的驱动程序，否则可能会出现无法找到设备或者安装不上驱动程序的现象。 一、Windows 7 下手动删除驱动程序的方法。 安装网站下载的即插即用驱动程序前，建议先手动删除打印机驱动程序，然后再安装驱动程序。 适用机型 HP LaserJet 1018、HP LaserJet 1020、HP LaserJet 1022、HP LaserJet P1505、HP LaserJet P1007、HP LaserJet P1008。 操作方法： 依次点击“开始（）”→“控制面板”，在“控制面板”窗口中，点击“设备和打印机”选项。 注:本文以HP LaserJet 1020 激光打印机的操作方法为例，其他型号打印机的操作方法也可以以此作为参考。

在“设备和打印机”窗口中，右键点击“HP LaserJet 1020”图标，选择“删除设备”菜单项。如图 1 删除设备所示： 图1: 删除设备 在“删除设备”窗口中，点击“是”按钮。如图 2 确认删除设备所示： 图2: 确认删除设备

必须断开USB 连接线，重新启动电脑。 重新启动电脑后不要进行任何打印操作。 在“设备和打印机”窗口中，点击“Microsoft XPS DocumentWriter”打印机图标，选择“打印服务器属性”菜单。如图 3 打印服务器属性所示： 图3: 打印服务器属性 在“打印服务器属性”窗口中，点击“驱动程序”选项卡，选择“HP LaserJet 1020”打印机型号，然后点击“删除”按钮。如图 4 属性所示：

(易错题精选)初中英语词汇辨析的难题汇编及解析

一、选择题 1．Is this a photo of your son? He looks________ in the blue T-shirt. A．lovely B．quietly C．beautiful D．happily 2．—Jerry looks so tired. He works too hard. —He has to ________ a family of four on his own. A．offer B．support C．provide D．remain 3．— Mr. Wilson, can I ask you some questions about your speech? — Certainly, feel __________ to ask me. A．good B．patient C．free D．happy 4．Some animals carry seeds from one place to another, ________ plants can spread to new places. A．so B．or C．but D．for 5．— Can you tell us about our new teacher? —Oh, I’m sorry. I know________ about him because I haven’t seen him before. A．something B．anything C．nothing D．everything 6．—Help yourselves! The drinks are ________ me. —Thank you. You’re always so generous. A．above B．in C．on D．over 7．Gina didn’t study medicine. ________, she decided to become an actor. A．Instead B．Again C．Anyway D．Also 8．—Have you got Kathy’s________ for her concert? —Yes, I’d like to go and enjoy it. A．interview B．information C．invitation D．introduction 9．More and more people have realized that clear waters and green mountains are as ________ as mountain of gold and silver. A．central B．harmful C．valuable D．careful 10．Kangkang usually does her homework ________ it is very late at night. A．until B．when C．before D．after 11．He ________all the “No Smoking” signs and lit up a cigarette. A．requested B．attacked C．protected D．ignored 12．一Where is Mr. Brown? 一I think he's _____________ the music hall. A．on B．in C．over D．from 13．— Is your home close to the school, Tom? — No, it's a long way, but I am________ late for school because I get up early daily. A．always B．usually C．never D．sometimes 14．—Mum, I don’t want the trousers. They’re too long.

英语现在进行时用法

英语现在进行时用法 初中英语――现在进行时 1】现在进行时的构成 现在进行时由"be+v-ing"构成。be应为助动词，初学者最容易漏掉，它应与主语的人称和数保持一致。 2】现在进行时的应用 在实际运用时，现在进行时常用以下几种情况： (1)当句子中有now时，常表示动作正在进行，这时要用现在进行时。如： They are playing basketball now.现在他们正在打篮球。 (2)以look, listen开头的句子，提示我们动作正进行，这时要用现在进行时。如： Listen！She is singing an English song.听，她正在唱英语歌。 (3)表示当前一段时间或现阶段正在进行的动作，且此时有this week, these days等时间状语，这时常用现在进行时。如： We are making model planes these days.这些天我们在做飞机模型。 (4)描述图片中的人物的动作，也为了表达更生动。此时也常用现在进行时。如： Look at the picture. The children are flying kites in the park.看这幅图，那些孩子正在公园放风筝。 3】现在进行时的变化 肯定句式：主语+be( am, is, are)+现在分词+其它. 否定句式：主语+be(am, is, are) +not +现在分词+其它. 一般疑问句：Be(am, is, are) +主语+现在分词+其它？ 特殊疑问句：疑问词+be(am, is, are)+主语+现在分词+其它？ 对现在进行时的特殊疑问句的回答，它不可以用Yes或No直接作答，要根据实际情况回答。 注意事项 1.在英语中，并不是所有的动词都要使用正在进行时。例如一些表示状态和感觉的动词，一般不用进行时态，而是用现在一般时表示。例如： I hear someone singing. 我正听见有人唱歌。

如何手动安装驱动

如何手动安装驱动？ 作者：Alright 编辑：Alright2010-01-11 10:27:59 13827 人阅读 把所有要安装的驱动程序都准备好后，我们就可以开始安装驱动程序了。驱动程序的安装方法也有很多种，下面就从易到难慢慢来看看。 1.安装傻瓜化——双击安装 现在硬件厂商已经越来越注重其产品的人性化，其中就包括将驱动程序的安装尽量简单化，所以很多驱动程序里都带有一个“Setup.exe”可执行文件，只要双击它，然后一路“Next（下一步）”就可以完成驱动程序的安装。有些硬件厂商提供的驱动程序光盘中加入了Autorun 自启动文件，只要将光盘放入到电脑的光驱中，光盘便会自动启动。 然后在启动界面中单击相应的驱动程序名称就可以自动开始安装过程，这种十分人性化的设计使安装驱动程序非常的方便。 2.从设备管理器里自己指定安装 如果驱动程序文件里没有Autorun自启动也没有有“Setup.exe”安装可执行文件怎么办？这时

我们就要自己指定驱动程序文件，手动安装了。 我们可以从设备管理器中来自己指定驱动程序的位置，然后进行安装。当然这个方法要事先准备好所要安装的驱动程序，该方法还适用于更新新版本的驱动程序。 首先从控制面板进入“系统属性”，然后依次点击“硬件”——“设备管理器”。 如图，网卡是没有安装驱动程序的设备，其前面会有感叹号“！”标示。 右键点击该设备，然后选择“更新驱动程序”。

接着就会弹出一个“硬件更新向导”，我们既然知道了它是属于什么型号的设备，而且还有它的驱动程序，选择“从列表或指定位置安装”。

如果驱动程序在光盘或软盘里，在接着在弹出的窗口里把“搜索可移动媒体”勾上就行，如果在硬盘里，则把“在搜索中包括这个位置”前面的复选框勾上，然后点“浏览”。接着找到咱们准备好的驱动程序文件夹，要注意的是很多硬件厂商会把其生产的很多类型的硬件设备驱动都压制在一张盘中，而且还会有不同的操作系统版本，如For Win2K（Win2000）和For WinXP的，要注意选择正确的设备和操作系统版本。点“确定”之后，点击“下一步”就行了。

【英语】英语形容词常见题型及答题技巧及练习题(含答案)及解析

【英语】英语形容词常见题型及答题技巧及练习题(含答案)及解析 一、初中英语形容词 1．My deskmate is really _____．She likes to attend different activities after school． A. active B. quiet C. lazy D. honest 【答案】 A 【解析】【分析】我的同桌同学非常活跃，放学后喜欢参加很多不同的活动． 句中提到"She likes to attend different activities after school"放学后喜欢参加很多不同的活动，由此推测此人非常活跃，A积极的，活跃的；B安静的；C懒惰的，D诚实的，根据句意可知选择A． 2．Wang Wei speaks English as ________ as Yang Lan. They both study English hard. A. good B. well C. better D. best 【答案】 B 【解析】【分析】句意：王伟的英语讲的和杨澜的一样好。他们学习英语都努力。可知as…as中间用形容词或副词原级；此处是副词修饰动词speak。good好的，形容词原形；well好地，副词原形，better比较级；best最高级，故选B。 【点评】此题考查形容词原级。注意as...as中间跟形容词或副词原级。 3．—If there are ________ people driving, there will be ________ air pollution. —Yes, and the air will be fresher. A. less; less B. less; fewer C. fewer; fewer D. fewer; less 【答案】 D 【解析】【分析】句意：——如果开车的人越少，空气污染越少。——是的，空气将会更新鲜。little少的，形容词，其比较级是less，修饰不可数名词，few几乎没有，形容词，其比较级是fewer，更少，修饰可数名词，people，可数名词，用fewer修饰，air pollution，空气污染，不可数名词，用less修饰，故选D。 【点评】考查形容词的辨析。注意less和fewer意思和用法。 4．—Guess what? The university has accepted my application! —Wow! That's ________ new I've heard this year, Boris! Let's celebrate. A. a worse B. the worst C. a better D. the best 【答案】 D 【解析】【分析】句意：——猜猜什么？那所大学已经接受我的申请了。——哇喔，那是今年我听到的最好的消息，Boris，让我们庆祝一下。A.一个更糟的，比较级；B.最糟的，最高级；C.一个更好的，比较级；D.最好的，最高级。因为大学接受申请了，所以是好消息，排除A、B。根据 I've heard this year，今年我听到的，可知是最高级，故选D。 【点评】考查形容词辨析，注意平时识记最高级结构，理解句意。

现在进行时的用法

现在进行时用法 一、定义：1、表示说话时正在进行的动作及行为2、表示现阶段正在进行的动作。 二、结构:现在进行时常有三种句型： （1）肯定式：主语＋be＋v-ing＋其它。如： He is mending his bike．他正在修自行车。 （2）否定式：主语＋be＋not＋v-ing＋其它。如： He is not（isn't） mending his bike．他没在修自行车。 （3）疑问式：主要分一般疑问句和特殊疑问句两种句式。 一般疑问句：Be＋主语＋v-ing＋其它？如： —Is he mending his bike？他正在修自行车吗？—Yes，he is．（No，he isn't．） 特殊疑问句：疑问词＋be＋主语＋v-ing＋其它？如： —What is he doing？他正在干什么？ 三、何时用现在进行时？ （1）以Look！或Listen！开头的句子提示我们说话时动作正在进行，应用现在进行时。如： Look！The children are playing games over there． Listen！Who's singing in the classroom？ （2）当句子中有now（现在）时，常表示说话时动作正在进行，这时也常用现在进行时。如：We are reading English now． （3）描述图片中的人物的动作时常用现在进行时，以示生动。如： Look at the picture．The girl is swimming．（4）表示当前一段时间内的活动或现阶段正在进行的动作时常用现在进行时。这时常与时间状语these days，this week等连用。如：

电脑驱动程序安装顺序

台式机和笔记本的驱动程序安装顺序 下表概述了在戴尔台式机和笔记本上安装驱动程序的正确顺序。重新安装Microsoft? Windows? 后，请按照列出的顺序来重新安装驱动程序。建议您打印此列表以供安装驱动程序时参考。 注：如果未按顺序安装驱动程序，某些设备可能无法正常工作。 1. 台式机系统软件 (DSS) 或笔记本系统软件 (NSS)—可为操作系统提供关键更新和补丁程序的重要实用程序。如果要重新安装 Windows 驱动程序或更新全部驱动程序，则一定要先安装该软件。 DSS和NSS位于 Drivers and Downloads (驱动程序和下载)页面上的System Utilities Category (系统公用程序类别)的栏目内。 2. 芯片组—帮助 Windows 控制系统主板组件和控制器。位于 Drivers and Downloads (驱动程序和下载)页面上的 ChipsetCategory(芯片组及智能卡类别)的栏目内。 3. 显卡—增强视频性能。位于 Drivers and Downloads (驱动程序和下载) 页面上的Video Category (显卡类别)的栏目内。 4. 集成网卡(NIC)—启用和增强用于互联网或有线网络访问的网络控制器。此类驱动程序位于Drivers and Downloads (驱动程序和下载)页面上的Network Category (网卡无线及蓝牙类别)的栏目内。 5. 仅限笔记电脑：Dell Quickset 或 Dell Control Point Manager (DCP)—控制笔记本电脑上的电源管理、环境光线传感器、无线配置文件和安全功能。此类驱动程序位于 Drivers and Downloads (驱动程序和下载)页面上的Applications (应用程序)的栏目内。 6. 声卡—启用和增强音频控制器。此类驱动程序位于 Drivers and Downloads (驱动程序和下载)页面上的Audio Category (声卡类别)的栏目内。 7. 调制解调器—具有拨号上网功能。此类驱动程序位于 Drivers and Downloads (驱动程序和下载)页面上的 Communication Category (Modem和通讯类别)的栏目内。 8. 无线网卡—启用和增强无线网络控制器。此类驱动程序位于 Drivers and Downloads (驱动程序和下载)页面上的Network Category (网卡无线及蓝牙)的栏目内。