104

Study on the interaction behavior of Geosynthetics and soil in China

Bao Chenggang Ningbo Institute of Technology, Zhejiang University, China, 315100 Yangtze River Scientific Research Institute, Wuhan, China, 430010

ABSTRACT: As a reinforcing material the geosynthetics are widely used in engineering practice to strengthen the foundation, slope, road, pavement, crushed-stone column, etc. However, the study on the reinforcement mechanism and the relevant design theory are much backward relative to the engineering application. As a result, the development of reinforcement technology was inhibited. The need for studying the interaction behavior between geosynthetics and soil has been realized by Chinese engineer. This paper firstly presents some typical views on the reinforcement mechanism in China. All the mechanism of reinforcement can be divided into two aspects: the direct reinforcement effect, which is resulted from the contact surface between soil and reinforced material, and the indirect reinforcement effect, which is resulted from the composite soil around the contact-face. Both effects have functions of improving rigidity, re-distributing stress and strain fields, changing the failure mode of soil, etc. Particularly, the mechanism associated with shear-band in the soil adjacent to contact-face is discussed in details. Thereafter, the results from laboratory tests, modeling tests and field observation are presented in the paper. Finally, the application of reinforced soil with geosynthetics in China is briefly introduced.

1 PREFACE

Reinforcement is one of most important functions of geosynthetics. In China, various kinds of geosynthetics are widely used in civil engineering, water resource and hydropower engineering, environmental engineering, etc. It has been demonstrated that the application of geosynthetics can bring great benefit to a project not only in engineering aspect, but also in economic and environment aspects. Also, it shows a promising future.

For the time being, the mechanism of reinforcement for geosynthetics is not fully understood, and hence the development in analysis method and design theory is backward as compared with its engineering application. Slope stability analyses are commonly performed to assess the contribution of geosynthetics reinforcement on the factor of safety (FS). It is found that the calculated FS is always too small to reflect the real effect. When the modified limit equilibrium method, such as circular slip surface method, is adopted for analysis, the obtained increase of FS due to geosynthetics reinforcement is only about 2-5%. When finite element method (FEM) is used for analysis, the increase of FS is only about 4%[1,2]. However, field observations for embankment on soft foundation indicate the limit height for an embankment can increase more than 30-100% as a result of geosynthetics reinforcement[3]. It indicates that the traditional analysis method is not perfect to reflect the reinforcement mechanism of geosynthetics in soils.

Being lack of reasonable analysis method and design theory, the development of reinforcement technology for geosynthetics is inhibited. Therefore, the mechanism of geosynthetics reinforcement, and its failure mode should be investigated urgently, and then reasonable analysis method and design theory should be proposed.

In the past, the concern of most Chinese researchers is how the circular slip surface method can still be used effectively in analysis of geosynthetics-reinforced structure. Some results have been published in Chinese literature. It showed that the circular slip surface method predicted 7% increase of FS when the balance of moment at the top face of reinforcement is considered. However, the simplified Bishop method predicted only about 2% increase of FS [4]. If the tensile effect is considered only at the part interesting with the slip surface, rather than whole contact face of reinforcing material, the value of FS tended to decrease[5]. If the redistribution of stress due to reinforcement is taken into account with a FEM method, the value of FS is increased significantly, which is closer to the real situation. However, it should be pointed out that all these studies are seldom related to the fundamental reinforcement mechanism and to the failure mode of geosynthetics-reinforced structure.

105

2 LIST OF THE VIEWS ON REINFORCEMENT MECHANISM

The following paragraphs present some current views on reinforcement mechanism. 2.1 Friction effect

The friction force is existed at the contact-face between soil and reinforcing material. Consequently, the horizontal displacement of the reinforced soil is restrained, the stiffness and strength of the soil is increased, and hence the stability of the soil structure is enhanced. Based on the friction mechanism, a certain of friction force was used to represent the reinforcement effect. Thus, the traditional analysis method can be used for stability analysis[6]. The friction force along the contact-face can be estimated according to the normal pressure and the coefficient of friction. 2.2 Constraint-induced strength

There is shear stress existing at contact surface, which results in a horizontal constraint effect on the reinforced soil. Hence, the horizontal stress of the soil element near the contact surface is increased byΔσ3, as shown in Fig. 1. Thus, the maximum principle stress at failure (σ1f) is much greater than the value for the un-reinforced case. It means, the reinforced soil is strengthened with respect to its shear strength and bearing capacity[7]. The constraint-induced strength can be described as “quasi-cohesive” (cR), while the value of friction angle (φR) is basically the same as that for the un-reinforced materials. The constraint-induced strength

(cR)can be written as: [ ]φθθθθθδθ tan)cos()sin()cos(

tancos∆++∆+⎥

⎦

⎤⎢⎣

⎡∆

= kcR . in which, k is a constant related to the

soil properties and characteristics of reinforcing material.θis an angle between the reinforcing material and the normal direction of failure surface, φ is the inner friction angle of soil, and δ is the friction angle of the contact surface between soil and reinforcing material (Fig. 2).

Fig1 Mohr stress circles for sand and reinforced sand

Fig2 Relationship between placing angle and quasi-cohesiveness

106

2.3 Tensile membrane theory

When soil foundation is settled by vertical load, the reinforcing material as a membrane lying on soil will be curved. The tension effect, which is induced by tensile membrane, will bear part of vertical load, so that the loading on the underlying soil is reduced. The stiffer the reinforcing material is, the greater the reinforcement effect will be. It can be imagined that the reinforcement effect is not closely related to the strength of reinforcing material, but it is significantly affected by the distribution of reinforcing material in the soil[10].

On the other hand, as the reinforcing material settles, the soil above reinforced soil layer will subside and the “arching effect” will also appear. It will enhance the stability of soil foundation[10]. 2.4 Stress-spreading effect by reinforced sand cushion

In soft foundation, the sand cushion is often used as a drainage for consolidation. The reinforced sand cushion also can spread the stress in the underlying soil. Hence, the stress delivered to the soft foundation will be reduced significantly. Based on the stability analysis, the increase of FS caused by friction action and stress-spreading effect is 15.7% and 44.7%, respectively, in which the pre-strain treatment is executed for reinforcing material. Moreover, for the reinforced composite foundation, the contribution of stress-spreading effect to reinforcement is greater than that induced by the tension effect of geotextile (i.e., “tensile membrane effect”)[11]. 2.5 Change of stress condition and deformation field

Another point is emphasized by Shen zhujiang: the stress condition of foundation is greatly influenced by friction force between reinforced materials and soil. If the material with enough strength is not pulled put or broken, the circular sliding failure will be impossible to appear in the reinforced soil. The most possible failure mode is lateral squeeze along with the soil settlement, so, the direction of shear stress will be changed due to existence of reinforcing material, then, the bearing capacity of foundation is increased remarkably[12].

Wang Wei’s analysis indicated that the displacement field in foundation is changed significantly as a result of reinforcement. In fact, a “self-support bearing system” (i.e. “quasi-rigid zone”) is basically formed in the composite soil foundation due to the existence of reinforced cushion[13]. 2.6 Shear-band theory

Research result shows the shear-band will appear in the zone adjacent to the contact surface between soil and geosynthetics when the shear strain reaching a certain extent. This is a new topic of bifurcation theory. The anti-sliding effect to contact surface by the localized deformation is an important aspect of reinforcement mechanism. It has led to many researchers’ attention[14,15,17].

3 ANALYSIS OF CHARACTERISTICS OF INTERFACE AND ITS EFFECT ON REINFORCEMENT

In this section, the author tries to analyze and summarize all the views related to reinforcement mechanism, and present the author’s standpoint.

Based on the review in the last section, all the reinforcement mechanism can be divided into two aspects: One is “The Direct Reinforcement Effect”, which is induced by interaction between soil and geosynthetics; the other is “The Indirect Reinforcement Effect”, which is resulted from the composite soil mass (quasi-rigid mass) formed by reinforcement material and adjacent thin soil layer.

As for the former one, the friction and interlocking effect, the “tensile membrane” effect at contact surface and particularly the “shear band” developed at the adjacent soil, will greatly increase the bearing capacity of foundation and delay the failure. It should be emphasized that the concept of “INTERFACE” is a zone with a certain thickness, including the contact face and its adjacent shear band. The ”interface effect” is a generalized term to express the comprehensive effect occurred at the interface.

For the latter one, owing to the re-distribution of stress and strain condition in foundation, the change in the direction of shear stress, the spreading effect of stress, the “arching effect” at up-lying soil layer, and the “quasi-rigid zone” beneath the reinforced layer extending to a certain depth is likely to change the failure

107

mode of soil, increasing bearing capacity notably and improving stability of soil structure greatly. This is just the “Indirect Reinforcement Effect” stated above in this section. It has been preliminarily verified by some experimental results obtained in China.

4 STUDY ON INTERFACE CHARACTERISTICS AND SHEAR BAND

As mentioned above, the direct aspect of reinforcement is resulted from the interface effect. The interface effect is firstly caused by the friction and interlocking effect at contact surface. The friction is induced by the relative displacement between reinforcement material and soil, while the interlocking is caused by the interaction of soil and geogrid (e.g., the traverse ribs of geogrid). However, the interlocking can only be appeared at large displacement condition. Thus, the two effects will probably be mobilized at different stages. It was indicated by the pullout test by Yan[19](see Fig.3). As relative displacement increases, the friction force also increases rapidly, and approaching to a stable value at the beginning of geogrid sliding. At that time, the resistance from the traverse ribs increases significantly, and gain the predominant role (90% of the total pullout face) in a short time. Meanwhile, the shear band will appear when the displacement of reinforcing material develops to a certain extent. One reason for the development of shear band is attributed to the friction and interlocking effect, and another one is related to the non-uniformity of reinforcing materials in quality. Even a small defect in reinforcement material may result in the non-uniformity of stress and strain[15].

Fig.3 Result from the pull-out test carried out in sand(after [19])

(sand, p=48kPa)

As a result of the high strain gradient, the shearing area will progressively propagate to the adjacent zone, and finally the shear band is formed. This is a problem of localized deformation and also the key issue of the interaction between soil and structure[14,15].

According to a large scale pull-out test[15], the surface of reinforcing material, even for geotextile, is a somewhat rough surface. The soil grain will be slid, rotated, crashed, etc, and then, the shear band is formed. The thickness of shear band is about 5~6 times of average size of soil grain. Therefore, the “interface” would include the “contact surface ” and the “shear band”. The behavior of interface is influenced by several factors: ① The roughness of contact surface. The rough contact surface will lead to anisotropic response of the stress-strain in interface, but the smooth contact-face does not (Fig. 4); ② The value of normal stress. If the normal stress is small, the deformation of interface exhibits a positive dilatancy, otherwise, it shows a negative dilatancy (see Fig. 5); ③ The properties of reinforced soil. The strength envelope line tends to change with the shape and friction angle of soil grains (i.e., sand, gravel or others). In China, many different types of soil are studied, including fine sand, silty sand, gravel, residual soil, volcanic ash, fine mining tails and soft soil. It is related to the extent of interlocking between geosynthetics and soil (see Fig. 6). Under this situation, the contact surface is no longer keeping a plane. This means the area of contact-face is increased, and hence the pull-out resistance is increased. The increase of shear strength due to the enlarged contact area can be termed as “dilatancy component of interface strength”. The consideration of this component will improve the accuracy of numerical analysis of interface[15].

Because of the localization phenomenon of deformation, the soil state in various part are rather different, the stress and strain behavior are also different, so the constitutive relationships are quite complicated. Hu[19] and Zhang[16] presented a constitutive model based on the Elasto-plastic Damage Theory. The FEM analysis result from this model is comparable with the result from a large scale pull-out test. The concept of “Damage” has a tentative meaning, not only to describe the deterioration of materials, but also to portray the evolution of one state to another one for material. This constitutive model combined the relationships of horizontal stress-strain

108

and normal stress-strain, and the coupling effect of shear and volumetric strains. It is termed as “Elasto-plastic Damage Constitutive model for soil-structure (reinforcement material) interface”, in short, “EPDI Model”. This model can reflect the behavior of strain softening, dilatancy and anisotropy etc.

Fig4 Results from soil-structure interface tests with respect to different roughness (after [17])

(σ=200kPa，Dr=90%)

Fig5 Cyclic test results for contact-face between gravel and geotextile under constant normal loading

(after [15])

Fig6 Strength envelope obtained from the pull-out tests with geotextile(after [15])

Fig. 7 and Fig. 8 show a comparison of results from numerical analysis by EPDI model and that from the

large-scale pull-out test. It is found that they are close to each other.

109

Fig7 Comparison of model prediction and experimental result for shearing along a interface between gravel

and geotextile (from [15])

Fig. 8 Modelling result for the relationship between pull-out resistance and normal stress of pull-out test

(based on EPDI model with geotextil) (after [15])

For the tensile membrane theory, Wang-Tao & Wang-Zhao have proposed an analysis model for reinforced pavement and obtained a general solution under symmetry and non-symmetry loading[18].

The relationship between pull-out force and pull-out displacement stated above is a fundamental data for numerical analysis of the geosynthetics-reinforced structure. It is also important for the application of geosynthetics reinforcement in engineering practice.

5 EXPERIMENTAL STUDY OF INTERFACE BEHAVIOR

5.1 Test method for soil-geosynthetics interface

Experiment is the most common approach to study quantitatively on the behavior of soil-geosynthetics interface. Experimental study generally includes laboratory tests (i.e., direct shear test, pull-out test, and triaxial compression test), model tests (i.e., static modeling test, and centrifugal modeling test), and field tests (i.e., in-situ test and field monitoring).

The direct shear test is to model the friction between soil and geosynthetics. It is shown, this test is simple and test result is regular. The stress-deformation relationship and shear strength parameters of interface can also be obtained. The pull-out test is good for simulating the friction and interlocking effect. The result is similar to direct shear test, but the value of c and Φ is perhaps slightly smaller than that from direct shear test. However, the result from pull-out test is not so regular as that from direct-shear test. As for triaxial test, the specimen is treated as a composite reinforced soil mass, and various testing condition can be controlled in triaxial test. The triaxial test results tend to reflect the behavior of whole reinforced soil mass under different conditions.

110

The static and centrifugal modeling tests are performed usually for some special engineering projects. The loading condition is quite similar to the pull-out test, particularly, with respect to stress level.

Some typical test results will be shown in following paragraphs. 5.2 Case I Direct shear test and pull-out test

Both direct shear test and pull-out test were performed for three types of reinforcing materials: warp-knitting geogrid, plastic geogrid with one direction tension, and woven geotxtile. Three kinds of soils are used for the tests, i.e., sand-gravel (Φ＝35.0°, c=0), coarse-sand (Φ＝31.5°, c=0) and granite residual soil(Φ＝23.9~29°c=14.6kPa). The size of the specimens for direct shear tests is 100×100×120 mm (i.e., length×width×height), and that for pull-out test is 200×200×60mm. The test results are shown in Table. 1 and Fig.9[20].

(a) Warp-knitted geogrid to gravel, direct shear test (b) Warp-knitted geogrid to gravel, pull-out shear test

Fig. 9 Shear stress versus displacement curves and shear strength envelope from laboratory tests

From Table 1, the behavior of interface is related to the characteristics of reinforcing material and the soil

properties. It is stated above the shear-band is sensitively influenced by the roughness of reinforcing material. The rougher, the lager the thickness of shear-band will be. Since the warp-knitted geogrid is roughest one and the interlocking effect is most significant, the shear-band is the thickest and the strength is the greatest. On the other hand, the greater the grain size, the higher the shear strength is. Also, more grains are mobilized in the shearing process.

Table 1. the result of the direct-shear test and pull-out test Direct-shear test Pull-out test

soil geosynthtic Csg/kpa Фsg/(°) (Фsg/Фs) Csg/kpa Фsg/(°) (Фsg/Фs)

plastic geogrid 2.0 30.5 0.84 2.6 33.6 0.96

warp-knitted geogrid 5.1 33.3 0.94 3.5 37.2 1.09 sand-gravel

woven geotextile 5.7 25.8 0.69 9.1 22.0 0.57

plastic geogrid 1.5 28.3 0.89 4.0 28.3 0.89

warp-knitted geogrid 5.4 30.2 0.95 0.8 32.6 1.05 coarse-sand

woven geotextile 3.0 27.2 0.84 1.8 31.3 1.00

warp-knitted geogrid 8.6 28.1 0.96 3.5 31.5 1.11 granite residual soil woven geotextile 2.3 27.4 0.93 7.0 26.9 0.93

*(Фsg/Фs) is the ratio of the friction of the interface and the friction of soil

Of course, the placement form of reinforcing material (such as, the number of material layers, interval, length, types of fixed end, pre-strain, etc.) also affects the test results [1,6,11].

111

5.3 Case II Triaxial test for reinforced soil with geogrid and crushed stone soil

In a large scale triaxial test[21], the size of specimen is 300 mm in diameter and 655 mm in height. The maximum grain size of the soil is 60 mm, and d60 is equal to 26 mm. The results demonstrate that the shear strength of the reinforced material is increased by about 29% for the specimens with 3 layers of geogrid (i.e., at an interval of 218mm), and by about 43% for 5 layers (i.e., at an interval of 131mm). The cohesion is also increased greatly. The test results indicate that the reinforced soil is no longer a pure disperse material, but somewhat continuum material. The stress-strain curve of the reinforced material exhibits a strain-hardening behavior instead of strain-softening behavior as observed for the un-reinforced one. It suggests that the reinforcement can improve the extensibility. Nevertheless, the reinforcing effect will only appear after the reinforced soil is deformed to a certain extent (say, ε＞1.0%), as shown in Fig.10. Another function of the reinforcement is to reduce the lateral and axial strain of soil. In this triaxial test, the deformation is decreased by 30%~60% for 3 layers of reinforcing material. The total compression of the specimens, particularly the differential settlement will be reduced and the bearing capacity is increased[34].

Fig. 10 Stress-strain curves under different ambient pressures (after [21])

5.4 Case III Static model test for spread foundation on aeolian sand[10]

The Aeolian sand is not a good foundation for a large structure. In this model test, geogrid is utilized. The purpose of this test is to study the stress and deformation, the failure mode and the reasonable placement form of reinforcing material (wrap-knitting geogrid). The aeoline sand is a fine sand, the grain size of which is very uniform, d80=0.25~0.1mm. The tensile strength of geogrid is about 60 kN.m-1, and the extensibility is 16.5%. Four types of placement, i.e., one layer, two layers, rectangle box type and long rectangle box type, are selected for comparison. The relationships between settlement and loading pressure are presented in Fig. 11.

Fig. 11 P-S curve for different types of placement of reinforcing material (after [10])

The results indicate the reinforcement effect for placement types of long rectangle box type is more

significant than the others. It is the failure occurring tardily, and the reinforced soil become more integral. The

112

failure process also shows that the soil beneath the footing is in compression state during the initial stage of loading. As the loading increases, geogrid starts to bend and settle, the tense membrane effect of geogrid appears due to the tension of the reinforcing material. At the same time, the “arching effect” occurs in the upper soil layer. Then, the stress in soil is spread beyond the “bending-settling plate”, and hence failure is delayed. 5.5 Case IV Centrifugal test

Centrifugal test can make a better simulation of stress level than the static model test [22]. Centrifugal test is also an effective way to study the reinforcement mechanism of geosynthetics and the reasonable distribution form for reinforcing material. The test results obtained by Yang, X. W.[23] indicated the stretching path of crack and fissure in soil will be changed as a result of reinforcement. The reinforcement tends to inhibit the joining-up of cracks, and hence the possibility of forming a throughout sliding surface would be reduced (see Fig.12). It is based on the test result and fracture theory.

Fig12 The change of stretching path of crack due to reinforcement (after [23])

6 APPLICATION OF REINFORCEMENT FUNCTION IN CHINA

The geosynthetics reinforcement has been widely used in engineering practice and yield great benefit in China. The main fields include reinforcement of soft foundation [24,25], reinforced retaining wall (the highest one is 55m[26,27,28]), preventing road pavement from reflection crack[29], reinforced stone-column with geogrid[30], vehicles jumped at bridge approach [31], reinforced permafrost soil in Tibet regions[32]. reinforced expansive soil slope[33], and so on.

Fig.13 shows the P-S curves for natural foundation and reinforced foundation[25]. Fig.14 shows a comparison between the monitoring result and the calculated result (Rankine theory) for a two-step retaining wall[27]. It is realized that it is possible to predict the behavior of reinforced structure in advance.

Test results and field observation also show the settlement of structures on soft foundation will be reduced not only for differential but for the total one[24].

Fig13 P-S curves for natural and reinforced foundation, field loading test (from [25])

113

Fig14 Comparision of horizontal pressure for observational and theoretical data

7 CONCLUSION REMARKS

The reinforcement of geosynthetics will change the behavior of natural soil from pure disperse material (non-cohesive soil) to somewhat continuum material. The stiffness, shear strength and bearing capacity of the reinforced soil are increased significantly. As a result, the stability of structure is increased, while both the total and differential settlements are reduced.

The reinforcement effect is mainly caused by “direct effect” from interface of reinforced soil and by “indirect effect” from the around “quasi-rigid zone” induced by reinforcement, the latter will alter the stress and strain fields as well as the failure mode.

Interface effect is the main factor to produce the reinforcement effect. The term of “interface” herein includes the contact face between soil and reinforcing materials, and the adjacent shearing band. The main factors affecting the development of shear band are the roughness of contact-face、grain size of reinforced soil and loading. Shear band would not be able to appear at smooth contact-face. Therefore, how to enhance the roughness at the contact surface is an important issue.

Interface behavior and the influence of “quasi-rigid zone” can be studied by the use of laboratory test, in-situ test, static modeling test and centrifugal modeling test, as well as field monitoring.

Based on the study of reinforcement mechanism and failure mode, the constitutive model and relevant numerical analysis method have been proposed for some special conditions. They will be useful for predicting the reinforcing effect. However, further research should be carried out, and verification in engineering practice is necessary and urgent.

ACKNOWLEDGMENTS

The great contributions for preparing this Key-note paper by Dr. Zhan Lian-tong and Senior Ding Jin-hua are very much appreciated. Thanks also to Prof. Wang Zheng-hong and Prof. Wang Zhao for checking this paper.

114

REFERENCE

Wang Zhao(editor), Study on application of geosynthetics in abroad, Modern Knowledge Press, Hong Kong 2002.5 151-155, 160-230, 376-411.(in Chinese)

Li-Dun engineering project of water supply(case history), Technology and application of geosynthetics in water resource engineering, Ge Wen-hui (editor), “ko xue pu ji press” 2000, 375-388 (in Chinese)

Rowe, R.K., “Geosynthetic reinforced enbankmemts on soft foundations”, Giroud Lecture, Proc. of 7th International Conference on geosynthetics, 2002, Nice, France

Chen Hong-jiang, Research on stability analysis method for embankment reinforced with geosyn. on soft foundation. Post proc. of Chinese symposium on reinforced soil engineering, Modern Knowledge Press, Hong Kong 2003,130-137(in Chinese)

Huang Zhuan-zhi etc., Sliding resistance of cushion reinforced with geosynthetic and its analysis method of stability, Post proc. of Chinese symposium on reinforced soil engineering, Modern Knowledge Press, Hong Kong 2003, 152-165 (in Chinese)

Application manual of Geosynthetics engineering (2th edition), China Construction Engineering Press, 2000, 218-232 (in Chinese)

Ashmany A.K. and Bourdeau P.L., “Effect of geotextile reinforcement on the stress-strain and volumetric simulation of dynamic behavior of soil with reinforcement”. Proc.of 6th Intern. Conf. on Geotextile, 1988. 1072-1082

Bauer C.E.&Zhou Y-J., “Effect of soil dilatancy on shear strength of reinforced composites”, Proc. of 5th International Conf. on Geotextile, 1994,369-372

Wang Tao, “The mechanism research and behavior analysis of reinforced pavement with geosynthetic”, [D] PhD thesis, Wuhan University, 2003.4 (in Chinese)

Li Chi & Liu Lin, “Study of indoor model test of spread foundation on the reinforced Aeolian Sand subgrade”, Chinese Journal of Geotechnical Engineering 25(4), 2003, 441-444 (in Chinese)

Xu Shou-man, “Stability analysis for soft foundation beneath embankment considering the comprehensive effect of reinforced cushion”, Proc. of 5th Chinese symposium on geosynthetics, Yichang, China, 2000, 411-414(in Chinese)

Shen Zhu- jiang, “Limit analysis of soft ground reinforced by geosynthetics”, Chinese Journal of Geotechnical Engineering 20(4), 1998, 82-86

Wang Wei, “Study on model tests and mechanism of soft soil foundation reinforced by geotextile”, Chinese Journal of Geotechnical Engineering 22(6), 2000, 750-753

Cai Zheng-yin, “Formation of shear band in cohesionless soils”, Chinese Journal of Geotechnical Engineering 25(2), 2003, 129-134 (in Chinese)

Zhang Ga, “A new monotonic and Cyclic Elasto-Plasticy Damage Theory for soil-structure interfaces”, PhD theses Tsing-hua University, 2002 10 (in Chinese)

Zhang Ga & Zhang Jian-min, “Development and application of Cyclic Shear Apparatus for soil-structure interface”, Chinese Journal of Geotechnical Engineering 25(2), 2003, 149-153 (in Chinese)

Hu Li-ming & Pu Jia-liu, “Experimental study on mechanical characteristics of soil- structure interface”, Chinese Journal of Geotechnical Engineering 23(4), 2001, 431-435 (in Chinese)

Wang Tao & Wang Zhao, “Model of geosynthetics reinforced pavements based on membrance effect”, Chinese Journal of Geotechnical Engineering 25(6), 2003, 706-709

Yan Shu-wang & Ben Barr, “FEM of soil-geogrid interaction with application to interpret the pull-out behavior of geogrid”, Chinese Journal of Geotechnical Engineering 19(6), 1997, 56-61 (in Chinese)

Ma Shi-dong, “Test study on soil interface characteristics of geosynthetics”, Journal of Yangtze Scientific Research Institute, 21[1], 2004 11-14 (in Chinese)

Zhao Chuan & Zhou, “Yi-Tang Experimental study on polymer geogrid reinforced crushed gravel by large scale triaxial test”, Rock and Soil Mechanics, 22(4) 419-422 (in Chinese)

Zhang Wei-min & Lai Zhong-zhong, “Study of centrifugal test of reinforced retaining wall”, China Civil Engineering Journal, 33(3) 2000, 84-91 (in Chinese)

Yang Xi-wu & Yi Zhi-jian, “Study on reasonable distribution of reinforcement for reinforced slope”, China Civil Engineering Journal, 35(4) 2002, 59-64 (in Chinese)

Lo Qian etc, “the experience research of geosynthetic-reinforced sand layer for reducing the settlement of soft foundition”, Chinese Journal of Geotechnical Engineering 25(6), 2003, 710-714 (in Chinese)

115

Ma Shi-dong, “Verification of effect of reinforced cushion with geogrid”, China Civil Engineering Journal, vol.37, 2004, (under printing) (in Chinese)

Lin Tang, “Study on tension of polypropylene compound reinforcement in super high reinforced earth retaining wall with three steps”, Chinese Journal of Geotechnical Engineering 24(4), 2002

Wang Xiang & Xu Lin-rong, “Test and analysis of two steps retaining wall reinforced by geogrid”, Chinese Journal of Geotechnical Engineering, 25(2) 220-224 (in Chinese)

Yu Xie-jian, Huang Guang-jun, Zhang Qian-li, Wei Dian-wu and Bao-heng, “Investigation of operating condition for two retaining walls reinforced with geotextile”, Proc. of 5th Chinese symposium on geosynthetics, Yichang, Hubei, China, 2000 519-522 (in Chinese)

Zhou Zhi-gang, Zhang Qi-sen and Zheng Jian-long, “Bridge-toughening analysis of reinforcement materials preventing bituminous surface from reflection crack by FEM”, China Civil Engineering Journal, 33 (1), 2000, 93-99 (in Chinese)

Zhou Zhi-gang & Zhang Qi-sen, “Analysis on the bearing capacity of geogrid reinforced stone columm”, Chinese Journal of Geotechnical Engineering, 19(1) 1997, 58-62 (in Chinese)

Tian Xiao-ge,Ying Rong-hua and Zhang Qi-sen, “Application of geogrid in solving the vehicles jumped at bridge approaches on soft foundation”, Proc. of 5th Chinese symposium on geosynthetics, Yichang, China, 2000 511-514 (in Chinese)

Su Yi, Xu Zhao-yi and Wang Lian-jun, “Study on deformation characters of reinforced embankment in permafrpse regine of Qinghai –Tibet railway”, Chinese Journal of Geotechnical Engineering, 26(1) 2004, 113-119 (in Chinese)

Wei Yong-xing, & MinWei-jing, “Design and construction for a high embankment of expansive soil at the section DK416 in Nuei-kun railway”, Proc. of 5th Chinese symposium on geosynthetics, Yichang, China, 2000 585-588 (in Chinese)

Wu Jing-hai, Wang De-qun and Chen Huan, “Study triaxial test of reinforced sand with geosynthetic”, Chinese Journal of Geotechnical Engineering, 22(2) 2000, 199-204 (in Chinese)

ContentsPrintRetune