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2004, 23 (17): 0-0 doi:

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MATHEMATICAL THEORY FOR ELASTIC SOLUTIONS IN
MULTILAYERED OR FUNCTIONALLY GRADED MATERIALS

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2004, 23 (17): 2845-2845 doi:

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A concise mathematical theory is summarized which was developed by the author over the last twenty years for analytically deriving solutions of three-dimensional boundary value problems encountered in elastic materials whose properties vary，continuously or in discrete steps，with depth from a surface exactly within the framework of elasticity. Such materials are now named as functionally graded materials(FGM). Some results are also presented that the author has obtained by using the theory in the analysis of various engineering problems. Such problems include elastodynamics，thermoelasticity，effect of imperfect bonding，ground land subsidence due to coal mining，design and evaluation of pavement structures，ground investigation with static cone penetration，soil consolidation，as well as fracture mechanics in functionally graded materials.

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DYNAMICAL MECHANISM AND STABILITY CRITERION OF LANDSLIDE UNDER LOCKUP OF SOIL ARCHING

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2004, 23 (17): 2855-2855 doi:

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Due to the fact that either there still exists an unbroken part on bedding-plane and/or flanks in landslide at the critical failure stage，or there appears a narrow and limited sliding path in front of sliding mass after the onset of landslide，a horizontal soil arching is developed across the narrow limits between the flanks of landslide，leading to restriction of deformation or braking of movement. In landslide，soil arch acts as a locked segment that gives direct support to soils over crown and prevents them from slipping downward，resulting in compacting and swelling of soil mass here. On the other hand，soil arch transfers the majority of vertical load above crown onto the arch abutment (double flanks in landslide) through the crown，which makes the abutment become the place of stress concentration. Once a rise of pore pressure by compaction of soils reduces shear strength on plane between arch and arch abutment to a low one so that one of the abutments fails keeping equilibrium，the crown would buckle completely giving rise to whole sliding of the landslide. The stress trajectories obtained from model test indicate that an arched region is composed of two different stress arches，i. e.，the maximum principal stress arch protruding upward and the minor principal stress arch dipping downward，and the computation model is proposed accordingly. It is supposed that the soil is in a state of plastic equilibrium and Mohr-Coulomb yield criterion is satisfied，the vertical load acting on the support arch is estimated by considering forces of self-weight of soils，shearing strength on bedding-plane，resistances at flanks，and stress redistribution caused by the soil arching effect. Consequently，the stability criterion of landslide is deduced and a practical case is analyzed，from which the presented study result is proved to be effective in the quantitative evaluation of stability of this kind of landslide.

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ANALYSIS ON SLOPE STABILITY OF EXPANSIVE SOILS

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2004, 23 (17): 2865-2865 doi:

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According to the failure shapes of expansive soil slopes，the failure types of expansive soil slopes are sorted into three kinds，slip in surface layer，slip in shallow layer and slip in deep layer. At the same time，their formation mechanisms are also discussed. Afterwards under considering the engineering characteristics of expansive soil and the environmental factors，the shear strength of expansive soil slope is considered as the variable varied with the depth and the stability of a middle expansive soil slope in Nanyang，Henan province，China，is analysed. The distributions of the safety factors are obtained and the shallow slip character of expansive soil slope is validated. Furthermore，based on these results，the slip surfaces of three failure types are investigated. Finally，the reasonable gradient of the analysed slope and the position of shallow slip surface are put forward.

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UNSTEADY SEEPAGE ANALYSIS OF TAILINGS DAMS CONSIDERING COUPLING OF STRESS AND SEEPAGE FIELDS

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2004, 23 (17): 2870-2870 doi:

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Based on the formation characteristics of tailings dams，the rigorous nonlinear analysis is made on the coupling of seepage and stress fields in tailings dams. Moreover，the governing differential equation is derived from the theory of elasticity and seepage on the coupling problem of stress and seepage fields. Then the corresponding finite element formulae and program are developing. Finally，the unsteady seepage analysis is made for the tailings dams. The result of an engineering example shows that the total seepage is less，but the maximum stress is bigger because of coupling considered.

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EXTENSION OF THREE-DIMENSIONAL SIMPLIFIED JANBU’S METHOD FOR SLOPE STABILITY ANALYSIS

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2004, 23 (17): 2876-2876 doi:

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Two-dimensional Janbu’s generalized procedure of slices is one of the rigorous methods for slope stability analysis. However，twice iterations must be carried out and the convergency problem may often be encountered in the computational process. Hence，a simplified Janbu’s method is developed in which the interslice shear forces are assumed to be zero and only once iteration is needed. Generally，the result obtained by simplified Janbu’s method is very close to that given by complete Janbu’s method，therefore the former is adopted in a number of commercial programs. It is natural to extend the 2D method to conduct 3D slope stability analysis.
Compared with two-dimensional slope stability analysis，it is more difficult to conduct three-dimensional analysis，for the geometric shape of the sliding body may be asymmetric and the slope may also possess complicated slip surface，irregular boundaries，and multiple geological layers.
The method proposed in this paper extends the simplified Janbu’s method for three-dimensional slope stability analysis. By setting the safety factors to be equal for discretized blocks on the same row/column and combining the geometric feature of the bottom slip surface，the local safety factor and potential sliding direction for each block can be obtained. This method extends traditional limit-equilibrium method in which only the total safety factor for a slope is given，thus it may be used to evaluate local stability and sliding direction for a slope. This proposed method may be applied to various types of potential slip surfaces，complicated geological boundaries and stratifications，water pressure，and earthquake loading.

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STUDY ON SLOPE CUT-INDUCED INFLUENCE
ZONE AND POTENTIAL SLIDE SURFACE

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2004, 23 (17): 2882-2882 doi:

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Determination of slope cut-induced influence zone and potential slide surface is an important problem for geotechnical field. The stress and strain at a particle in slope are readjusted when the slope is cut. According to the readjusting regularity of stress and strain，the influence zone and potential slide surface are determined，with the help of wedge theory of elastic mechanics. A practical case study is made and the result proves that the presented method is reasonable.

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STRENGTH CHRACTERISTICS OF SOIL IN SLIDE ZONE AND
DETERMINATION OF ITS PARAMETERS

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2004, 23 (17): 2887-2887 doi:

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The strength parameters of soil in slide zone are indispensable factors for stability evaluation and control design to a landslide. In this paper，the strength characteristics of soil in slide zone are analyzed，and the residual strength parameters and the restorative strength parameters of the soil in slide zone are discussed，too. The implication of the stability safety factor for landslide and the strength parameters of soil in slide zone is gotten clear through discussion about the definition of the stability safety factor for landslide. The method of determination of the strength parameters of soil in slide zone is proposed. Combined with the practice of Gushubao landslide，the strength parameters of soil in slide zone are determined.

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CENTRIFUGE MODELING TEST ON REINFORCED EARTH WALL AT WUSHAN COUNTY IN RESERVOIR AREA OF THREE GORGES PROJECT

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2004, 23 (17): 2893-2893 doi:

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Centrifuge modeling test is made to study the support mechanism of reinforced earth wall with the height of 57 m at Wushan county in the reservoir area of Three Gorges Project. The earth pressure of the wall and tensile stress of reinforcement are studied in detail. The model manufacture and test process are introduced systematically in the paper. It is shown that the earth pressure of the wall is distributed with greater value in the middle and less one at the bottom and the top，i.e.，the earth pressure is increased up to its maximum value first and then decreased with the height of wall. It is also shown that the stress of reinforcement is increased with outside loading and there are two maximum values of the reinforcement stress changed with time.

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REVIEW ON DISPLACEMENT BACK ANALYSIS FOR PERMANENT SHIPLOCK SLOPE OF THREE GORGES PROJECT

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2004, 23 (17): 2902-2902 doi:

[PDF] 651 KB (906)

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The main research achievements are summarized of the displacement back analysis for the permanent shiplock slope of the Three Gorges Project during its excavations of stage 1 and 2，from 1994 to 2000. The deformation mechanism and its numerical modeling of rock slopes are presented. For the back analysis of rock slope，theoretical research is important，however for engineering application, more attention should be paid to the investigation of its macro-deformation mechanism and numerical modeling technique. For the blocky rock masses of the permanent shiplock slope，their deformation is primarily composed of that of its disturbed zone，and it is feasible to model the deformation behavior of the disturbed zone by taking it as a weakened linear-elastic material.

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KEY TECHNOLOGIES FOR SAFETY MONITORING OF HIGH-ROCK SLOPE OF PERMANENT SHIPLOCK OF THREE GORGES PROJECT

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2004, 23 (17): 2907-2907 doi:

[PDF] 205 KB (1170)

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The safety problems of high-rock slope of the permanent shiplock of Three Gorges Project are analyzed. The design principles of safety monitoring are proposed. Based on the stability problems of high-rock slope of the permanent shiplock of Three Gorges Project，the monitoring demands are presented. According to the monitoring sections，the optimization design of monitoring items and instruments are proposed. The practical example shows that the proposed scheme is feasible and effective.

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STABILITY ANALYSIS OF LANDSLIDE IN THE SOUTH END
OF FENGJIE HIGHWAY BRIDGE WITH FLUCTUATION
OF WATER LEVEL OF THREE GORGES RESERVOIR

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2004, 23 (17): 2913-2913 doi:

[PDF] 638 KB (1207)

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After the TGP dam was built，the reservoir will be impounded gradually till the level ascends at least 100 m in about 10 years. As the need of flood prevention，the reservoir water level will fluctuate between 175 m and 145 m. The periodical rise and descent of water level will change the intrinsic water-rock interaction circumstance and condition，which maybe results in the instability of reservoir banks and slopes. Under the fluctuation of different water levels，the seepage-stress fields，the deformation trends and the failure process of landslide are analysed using FLAC4.0. In addition，the change of landslide stability and its influence on bridge foundation after water level fluctuations are discussed in this paper. All these research results will provide technical supports for the stability assess of bridge foundation and the design of project prevention.

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CONTRIBUTION RATE RESEARCH OF STRATUM TO LANDSLIDE GROWTH OF YUNYANG—WUSHAN SEGMENT IN THREE GORGES RESERVOIR REGION

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2004, 23 (17): 2920-2920 doi:

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The contribution rate of stratum to landslide growth of Yunyang-Wushan segment in Three Gorges reservoir region is analyzed by statistical information method of GIS and statistical overlaying method. The result indicates that three kinds of strata make contribution to the landslide among 20 kinds of strata. The presented method can be used to quantitatively analyze different effect of different strata on landslide growth，and new analysis method is offered for formation research of regional landslide. By using the new method，the shortage of traditional methods is overcomed，and the analysis result will be more reliable.

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MODEL AND METHOD FOR RISK ZONING OF RESERVOIR-INDUCED EARTHQUAKE IN HYDROPOWER PROJECT AND ITS NEIGHBORING AREA

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2004, 23 (17): 2925-2925 doi:

[PDF] 938 KB (983)

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Like the natural earthquake activity，the induced earthquake risk in hydropower project and its neighboring area is spatially heterogeneous. It is not reasonable only to take the hydropower project as a whole to predict its potential earthquake. The analysis and assessment of the induced earthquake risk should be made at different location around the project. According to this requirement，the risk zoning concept of induced earthquake is proposed，and the corresponding theory and method are preliminarily discussed. A probabilistic model to calculate the different levels of reservoir-induced earthquake risk at every location around the hydropower project is constructed. As a test，the risk zoning of induced earthquake in Yangtze Three Gorges reservoir and its neighboring area is carried out，and the probability distribution maps of different levels of reservoir-induced earthquake risk around Yangtze Three Gorges project are given out.

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APPLICATION OF CSAMT TO PROSPECTING ACTIVE FAULT

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2004, 23 (17): 2932-2932 doi:

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The feasibility problem of application of CSAMT to prospecting active fault in the West Route of South-to-North Water Transfer Project is studied. The study results show that CSAMT can be applied to prospect the characteristics of deep region of active fault for engineering design. Some beneficial conclusion and advice about geological prospect are obtained.

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APPLICATION OF ELASTIC WAVE WELL LOGGING TO STRATUM ASSESSMENT OF THREE GORGES RESERVOIR BANK

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2004, 23 (17): 2937-2937 doi:

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The interbedding of soft and rigid layers or interbedding of cataclastic and integrative layers in Three Gorges reservoir bank gives rise to difficulties in engineering geology assessment and accurate classification of mantle rock. The elastic wave well logging and separate measurement of Vs and Vp are described to classify the mantle rock and calculate geotechnical kinetic parameters. A case study is made to show the availability of the proposed method.

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2004, 23 (17): 2943-2943 doi:

[PDF] 264 KB (801)

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DETERMINATION OF RATIONAL SLOPE ANGLE CONSIDERING INFLUENCE OF BLASTING VIBRATION ON OPEN-PIT MINE IN MOUNTAINOUS AREAS

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2004, 23 (17): 2949-2949 doi:

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The landslip of rock slope with the influence of blasting vibration often results in serious disasters，frequently with heavy losses of life and damage to property. It is generally difficult to precisely analyze rock slope stability due to the vast number of unknown variables，such as slope type，height and angle of slope，physical properties of rock mass，and so on. The prediction of failure of rock slope is an important problem of rock mechanics in the engineering excavation activities，especially the open-pit mine in mountainous areas. It is difficult to determine the rational slope angle of rock slope because of the complexity of the problem. Recently，fuzzy theory has been applied to predict the landslip and failure of rock slope. The landslip of rock slope can be regarded as a fuzzy event. The landslip will take place at a fuzzy probability，and so the theory of fuzzy measures can be applied to predict the landslip and failure of rock slope. By using statistical analysis，the initial damage of the rock slope in mountainous areas is found to be of normal distribution. Based on the results of statistical analysis of a large amount of measured data in slope engineering，the fundamental fuzzy model of failure of rock slope is established by using the theory of fuzzy mathematics. The formulas of two-dimensional problems are derived and applied to the prediction of slope failure due to surface mining. The fuzzy measure models are adopted for determination of rational slope angle considering the influence of the blasting vibration on open-pit mine in mountainous areas. The fuzzy failure probability and dynamic responses of the rock slope are calculated. Numerical results are compared with those obtained from independent field tests. The agreement of the theoretical results with the field measurement shows that the presented model is satisfactory and the formulas obtained are valid，and thus can be effectively used for prediction of slope failure and determination of the rational slope angle of rock slope.

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RESPONSE OF HUANGMAILING ROCK SLOPE TO EXPLOSION

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2004, 23 (17): 2954-2954 doi:

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The regularity of wave velocity attenuation of Huangmailin rock slope under explosion is analyzed based on the monitoring of explosion-induced vibration and sonic wave testing in field. The influence of explosive charge on the property of slope rocks is studied. The safety threshold of velocity for the rock slope under explosion is proposed，and the study result has been successfully applied to Huangmailing phosphorus mine.

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RESEARCH ON BEHAVIOUR OF SOIL LIQUEFACTION FOR THE ROADBED OF RAILROAD IN TANGZHANG TOWN，XUZHOU CITY

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2004, 23 (17): 2959-2959 doi:

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Based on the model of pore pressure increment of soil and the data of dynamic triaxial test of soil，the seismic response analysis of liquefaction ground is made for the roadbed of railroad in Tangzhang town，Xuzhou city，by using finite element method. The liquefaction districting of saturated silty soil layer is made according to the comparative analysis of pore pressure ratio of soil and dynamic shear stress on the largest shear surface with going back and forth. Combined with liquefaction differentiation results of standard penetration test，shear wave velocity test and Seed-Idriss simplification method，the comprehensive evaluation is made on the behaviour of earthquake-induced liquefaction of silty soil layer of the railroad roadbed.

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STUDY ON FAILURE CHARACTERISTICS AND ULTIMATE PULLOUT
FORCE OF PRESTRESSED CABLE

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2004, 23 (17): 2966-2966 doi:

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Based on testing data，a biparametric equation is presented to depict the rupture shape of prestressed cable. According to the ultimate equilibrium principle and Hoek-Brown criterion，the ultimate pullout force of prestressed cable is studied and a ultimate-value principle is suggested. A calculation example is given. The results show that the ultimate pullout force is related to the rupture shape of prestressed cable，rock type，unconfined compressive strength of rock，weathering degree，grouting material and grouting pressure，etc. At last，a series of formulas are given to determine the ultimate pullout force and lateral resistance of prestressed cable.

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DISCUSSION ON DESIGN PRINCIPLE AND METHOD OF
PRESTRESSED CABLE FOR SUPPORT OF ROCK SLOPES

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2004, 23 (17): 2972-2972 doi:

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The working mechanism of prestressed cable，design of prestress value，interval of the multi-cables，length of cable，anchorage angle and strength parameter of the prestressed body are systematically analyzed and discussed in this paper. Some meaningful conclusions are obtained.

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FIELD TESTING STUDY ON COMPOSITE FOUNDATION OF
DJM PILE UNDER ROAD EMBANKMENT

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2004, 23 (17): 2977-2977 doi:

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The behaviors of composite foundation of DJM pile were studied through field test，including settlement，deep horizontal displacement，excess pore water pressure，stress ratio of pile to soil，and pile strain. The test results show that (1) the post-construction settlement can meet design requirements，(2) the settlement transits smoothly from the bridge pier to road embankments when the pile length is gradually changed，(3) the deep horizontal displacement of foundation is small enough to keep foundation stable and reduce the influence of foundation on bridge pier，(4) the excess pore water pressure dissipates slowly，but it¢s value is not large enough to have evident influence on stability of the settlement，(5) the stress ration of pile to soil is large in this case，and (6) there is linear relationship between soil pressure and DJM pile strain.

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ANALYSIS ON FROST HEAVING OF PLATE FOUNDATION USING FRACTURE MECHANICS METHOD

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2004, 23 (17): 2983-2983 doi:

[PDF] 279 KB (992)

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Based on fracture mechanics theory，a general failure criterion is set up and a fully new analysis method is given for plate foundation and ground widely used in cold regions. Frost heaving force and flaws of frozen soil are considered in the criterion，and the criterion would be more reasonable and more practical than conventional one. The stability of frost heaving for plate foundations embedded deeper and shallower than freezing-depth are analyzed，and the strength analysis method for failure of bottom plate of water pool is proposed as well. After that，practical samples are analyzed by different methods，from which the validity of the new method is gotten.

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ELASTO-PLASTIC ANALYSIS METHOD FOR VERTICAL
PILE BASED ON MINDLIN’S SOLUTION

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2004, 23 (17): 2988-2988 doi:

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Based on Mindlin’s solution，it is assumed that pile is elastic，and there is relative displacement between pile and soil，and a group of equations are established and solved by finite difference method. Two examples are given，and the calculated results agreed well with testing data. The advantage of this method is that the interaction of pile and pile，and pile and soil can be considered.

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STUDY OF STRESS DISTRIBUTION IN BELT GEOSYNTHETIC-REINFORCED GRAVEL ON SOFT SOIL

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2004, 23 (17): 2992-2992 doi:

[PDF] 257 KB (1158)

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Load tests in field are carried out for belt geosynthetic-reinforced gravel layers to study the strength and modulus characteristics of geosynthetic-reinforced foundation on soft soil. The effects are analyzed of numbers of reinforcement layers，distance from footing bottom to top reinforcement layer，interval of reinforcement layers and linear density of reinforcement on the angle of stress spread in foundation. It can be summaried that the angle of stress spread in foundation is obviously increased to larger than 20° after reinforcement by geosynthetic belt. The main affecting factors among above 4 parameters are the numbers of reinforcement layers and interval of reinforcement layers. Thus it is suggested that the angle of stress spread of geosynthetic-reinforced layer may be free from the limit of Chinese Code for Design of Building Foundation(GB50007-2002).

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REINFORCEMENT METHOD OF LACUSTRINE SOFT SOIL FOUNDATION

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2004, 23 (17): 2998-2998 doi:

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There are many engineering methods to reinforce soft soil foundation. For different methods，the effect，cost and construction period may be very different，and it is difficult to consider all the aspects well. The step-loading method combined with draining-board has advantages of low cost and good result to soft soils，but the construction period is quite long. In the engineering of rockfill dam for new tailing storage of Wushan copper-mine，a large single layer loading method was used to reinforce the lacustrine soft soil foundation. The data of pore water pressure of foundation together with other parameters were used to control the loading speed. The stability of foundation was kept and the construction period was shortened. With the presented method，the cost，effect and construction period can be well considered simultaneously.

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DYNAMOSTATIC ANALYSIS OF PROPERTIES OF EXPANSIVE
SOIL AND IMPROVED SOIL

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2004, 23 (17): 3003-3003 doi:

[PDF] 286 KB (1171)

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The physical properties of expansive soil and improved one are researched，and the dynamostatic triaxial tests are made on the two kind of soils. Compared with the other material，it is found that the stress-strain curve of expansive soil behaves as strain hardening，while that of improved expansive soil behaves as strain softening. The static strength and cohesion of improved expansive soil are bigger than that of expansive soil. There is a threshold of dynamical stress which divides the deformation of soil into steady-state deformation and destructive-state deformation for the two kinds of soils. The experimental formula between the cumulative plastic strain and the number of cycles of dynamic load is set up，and the dynamical stress-strain curve and dynamical elastic modulus-elastic strain curve for two kinds of soil are also studied. According to the testing results，it is not found for the frequency of dynamical load to affect the deformation of soils obviously.

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TESTING STUDY ON MOISTURE CONTENT OF STANDARD ABSORPTION FOR EXPANSIVE SOIL

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2004, 23 (17): 3009-3009 doi:

[PDF] 245 KB (1455)

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Under the given condition of humidity of 60% and temperature of 25℃，two kinds of expansive soil are used for testing study on moisture content of standard absorption. One is mixed samples of kaolinite and montmorillonite in laboratory whose montmorillonite contents are 100%，50%，30%，20%，10% and 0，respectively，and another is expansive soil samples from three basins of Guangxi province，China. There is great difference between the moisture contents of standard absorption for soil from the tests of moisture absorption and dehydration. The physical definition of moisture content of standard absorption for soil from dehydration is clear and stable，so that 60% of moisture content of equilibrious absorption from dehydration is taken as the definition of moisture content of quasi-absorption. The moisture content of standard absorption for soil shows a linearity correlation with montmorillonite content，liquid limit，plasticity index and free expansive ratio of expansive soil，which reflects essential property of expansive soil，and is an important information to distinguish and classify expansive soils. The test method presented in this paper is simple and easy to run，so that the soil samples may basically arrive at stable state in 72 hours.

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APPLICATION OF MICROTREMOR TO SITE EVALUATION IN FUZHOU

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2004, 23 (17): 3014-3014 doi:

[PDF] 373 KB (1234)

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The dynamical characteristics of ground soil and structure of frequency spectrum of ground microtremor in Fuzhou，Fujian province，are studied in this paper. The ground microtremor signals were observed，and the signals were analyzed by fast Fourier transform method (FFT). The characteristics of structure of frequency spectrum and response of ground soil to frequency of ground microtremor are revealed， and the function of microtremor with frequency-dependence and frequency-selection for different foundation soil strata is also researched. The results are shown as follows. First，ground microtremor is a kind of geophysics information with abundant intension. The frequency characteristics of ground microtremor can be obtained by spectral analyses of its signals，which can be used to probe into dynamical characteristics of rock and soil of studied area. Secondly，there exists a function with frequency-dependence and frequency-selection for the response of site soil. The change of predominant period of ground microtremor is closely related to the formation of site soil layers，and mutually corresponds to the change of engineering geological conditions of the site. Therefore，the structure and feature of different foundation soil strata can be distinguished with different kinds of frequency response of site. Thirdly，the structure of rock and soil layers directly influences the spectral structure characteristics of ground microtremor. The covered layer with the structure of different foundation soil strata is related to the frequency of ground microtremor. The thickness of covered layer is one of important factors to affect the predominant period of ground microtremor. Fourthly，there exist some corresponding relationships between spectral structure characters of ground microtremor and shear wave velocity of site soil layers. The outcomes of these two kinds of tests can be conferred each other. Fifthly，the correlations among predominant period of ground microtremor，thickness，and value of shear wave velocity of covered layer are established. The study results have been applied to selecting the infrastructure and buried depth of high building foundation in the coastal area of Fujian province.

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SUPPORT DESIGN PRACTICE USING SOIL NAILING WALL IN GUANGZHOU KAIHUACHENG DEEP FOUNDATION PIT

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2004, 23 (17): 3021-3021 doi:

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The scale of Kaihuacheng deep foundation pit in Guangzhou is quite large，with depth of 10.7～12.3 m. The strata of the pit field mainly consist of plastic alluvial silty clay，plastic～stiff plastic residual silty clay，and medium compact residual silt. The neighbouring environment is complicated. The support design practice of the pit using soil nailing is presented in this paper. Some affecting factors are considered and measures adopted in order to control the displacement of the pit. Nails are arranged with alternation of long and short lengths. Prestressed bolts are installed on upper part of the pit slope in some deeper and steeper segments. Certain slope angle，1∶0.6 or 1∶0.2，is adopted in some segments according to the condition of the field. Minitype steel pipe piles are installed for advance support in vertical digging segment. The characteristics of pit displacement and the reason why big horizontal displacement occurs are analysed. The support result of the pit is also evaluated.

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DISCUSSION ON IMBALANCE THRUST FORCE METHOD
AND SARMA’S METHOD

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2004, 23 (17): 3030-3030 doi:

[PDF] 285 KB (1577)

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Imbalance thrust force method (ITFM) is originally developed approach for slope stability analysis in China，which has been widely used in the field of landslide stability analysis. But few papers are interested in the accuracy of results obtained by ITFM. It has been proved that the error by ITFM is high enough not to be negligible，and the hidden danger will take place in practice if misusing it. By theoretical analysis and comparison of examples，it is considered that the accuracy of ITFM is influenced by the increments of slip segment obliqueness，and the accuracy can be improved by adjusting the increments of slip segment obliqueness. The increments of slip segment obliqueness must be less than or equal to 10 degrees when using ITFM，otherwise the other slope stability analysis methods should be selected or the slip line should be improved. A new inter-slice shear force equation is presented in this paper to solve the existing problems in the inter-slice shear force equation of Sarma′s method. The presented equation meets the demands of slope stability analysis，and can properly express inter-slice shear forces for general slices. Sarma′s method is improved，based on the new inter-slice shear force equation. The improved Sarma′s method considers that the reduction factor for shear strength along inter-slice boundary is different from that for shear strength along slip surface. Corresponding examples indicate that the improved Sarma′s method works better than Sarma′s method and a more reasonable value of safety factor can be obtained by the improved Sarma′s method. The consistent values of safety factor can be given and the iteration is stably convergent even if the shape of slices is varied.