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2007, 26 (07): -0 doi:
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LOESS IN CHINA AND LOESS LANDSLIDES

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2007, 26 (07): -1297 doi:
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Loess in China is world-famous for its stratigraphical intactness，huge total thickness，vast expanse of distribution and noticeably metastable geotechnical properties. In distribution，loess spreads outward from the “Central Loess Plateau”composed of Shanxi，Shaanxi and Gansu provinces as the main body and blankets a total land area of 6.3×105 km2. During the Quaternary Period，the prevalent arid，semi-arid climatic environment provided the stage on which material sources came into being，grain particles were wind-transported and deposited and loess strata were thus formed，with almost coincident erosion. In this manner，the spectacular loess geomorphological features and landforms evolved. In the processes，the landslides have been either the end results thereof or active participants. The paper puts emphasis on the granulometry and engineering properties which are peculiar to and characteristic of loessial deposits as well as the role they might play in the initiation and evolution of loess landslides，giving them due coverage and reiterating in the meanwhile the fact that there exists a regular，gradual change(amelioration) of the main geotechnical properties of loess in the direction from Northwest to Southeast all across the“Loess Plateau”. From this point，the paper proceeds to discussion of such problems as geomorphological zonation，landslide distribution，structural features of loess landslides as well as their sliding mechanisms. In the brief review of landslide-triggering problems，that of seismic landslides is given due attention. This is followed by a summing-up of the methods of landslide prevention and remediation that are currently in use in China and have been time and again proven to be effective. As illustrations in this regard，several successful cases and experiences therefrom are cited. Finally，in the closing remarks，the issues that need more attention and further in-depth research are raised and briefly discussed.

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QUANTITATIVE TEST STUDY ON MESOSTRUCTURE OF ROCK

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2007, 26 (07): -1313 doi:
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Rock is a multiscale material，and in the past，the research of rock in macroscopic scale is much more than that in mesoscale. But the damage and failure of rock under loading are caused by the propagation and coalescent of cracks at mesoscale，so it is helpful to understand the mechanical behaviours of rock by quantitatively investigating on mesostructure of rocks. The quantitative test on mesostructure of rock is designed based on damage mechanics. A great deal of mesostructural images of Jinping marble in Sichuan Province have been obtained by means of scanning electron microscopy(SEM). The mesostructural images of marble are processed by regional growing theory based on image processing technique. According to stereology theory，the program is compiled by MATLAB to enhance the details of images and execute the image segmentation. The mesostructural information of rock microcracks such as length，angle，width，area，perimeter，etc. are obtained from binary images after segmentation. Then，the mesostructural information of microcracks is analyzed by statistical theory and the distribution regularities of microcrack parameters are proposed. Based on the statistical regularities of the mesostructural parameters，the representative element volume(REV) of rock in mesoscale is simulated by using the Monte Carlo theory. Finally，the initial damage tensor of REV of rock in mesoscale is obtained according to the geometrical damage mechanics；and it is used in the G. Swoboda damage model to obtain the stress-strain relations under the conditions of uniaxial and triaxial compression loads. By comparing the simulated result with the actual experiment result of stress-strain relationships，it shows that the simulation of two conditions nicely agree with in-situ test results.

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VISCOELASTIC PROPERTIES AND A MECHANICAL MODEL FOR POROUS ROCKS UNDER AIR-DRIED AND WATER-SATURATED CONDITIONS

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2007, 26 (07): -1325 doi:
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Viscoelastic properties during deformation are especially notable for porous rocks such as tuff and weathered rocks. The authors study the deformation characteristics of porous rocks，and propose a new rheological model based on constitutive equations previously proposed by the authors. The model consists of a spring and a dashpot. It is assumed that the constitutive equation described in a previous study can be applied to the spring. The viscosity of the dashpot is low before loading，and increases gradually with progressive loading. In creep testing at low stress levels，strain of the dashpot has close relationship with creep strain because the spring constant does not decrease significantly at low stress levels. The shape of the stress-strain curve and the loading rate-dependence of the peak strength can be explained according to the proposed rheological model. To compare the theoretical predictions with the test results，four kinds of rocks including muddy sandstone，Oya tuff，Tage tuff and Kawazu tuff are employed. The theoretical stress-strain curves are well consistent with the measured curves. The key result of this study is that even at low stress conditions，strain of the dashpot is considerably larger than that considered in previous studies. By this model，the difference of Young¢s moduli between air-dried and water-saturated conditions is well simulated where the difference in Young¢s modulus is assumed to be the difference in strain of the dashpot. Under water-saturated condition，strain of the dashpot increases more rapidly；and then Young¢s modulus is relatively small. The differences in the irrecoverable strain for wet and dry rocks are the reasons for the differences between the Young¢s moduli of wet and dry rocks.

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NEW METHOD FOR SURFACE VEGETALIZATION OF SLOPES REINFORCED WITH ANCHORING BAR AND SHOTCRETE STRUCTURE

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2007, 26 (07): -1333 doi:
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For bare slopes caused by engineering construction，it is one of effective reinforcement methods for maintaining long-term stability of the slopes to utilize anchor and shotcrete structures. However，applications of the reinforcement method will lead to some negative problems for environmental protection，i.e. destroying original vegetations，not being harmonized with surroundings，and so on. Most slope greening methods are not suitable for slopes with slope angles larger than 60°，but the slopes reinforced with anchoring bar and shotcrete structures can usually be adopted for slope with a larger slope angle. For this reason，a new method for surface vegetalization of slopes reinforced with anchor and shotcrete is developed. In this method，spaces for plant growth are separated from the anchoring bar and shotcrete structures，but they have some mutual relations in following two points：firstly，establishments for plant growth can be fixed by using anchoring bars and shotcrete；and secondly，water for plant growth can be partly supplied by drainage holes arranged in anchoring bar and shotcrete structures. In the view，utilizing this method will not only ensure enough spaces for plant growth，but avoid potential damages of plants to the anchoring bar and shotcrete structures.

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STUDY ON DETERMINING METHOD FOR PARAMETERS OF ROCK¢S SHEAR STRENGTH BASED ON ASYMMETRIC
TRIANGULAR FUZZY NUMBERS

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2007, 26 (07): -1340 doi:
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Aiming at the randomness and fuzziness for determining parameters of rock¢s shear strength，firstly，a method is put forward to express parameters of rock¢s shear strength using asymmetric triangular fuzzy numbers，which can reflect the interval features and probability distribution of parameters of rock¢s shear strength. Secondly，the sum of interval width of asymmetric triangular fuzzy numbers under some cut level together with square of the difference of weight between testing values and most probability calculation values is regarded as objective function for fuzzy optimistic analysis；and the determining method for the suitable cut level of asymmetric triangular fuzzy number is proposed by using “3s” rule. Then，the approach to determine the reasonable cut level of asymmetric triangular number is developed；accordingly，a new method to determine parameters of rock¢s shear strength based on asymmetric triangular fuzzy numbers is established. This method can reduce the effect of abnormal testing data on the most probability analysis results and can reflect the uncertainty features for determining the parameters of rock¢s shear strength. It can provide a new method for deciding values of mechanical parameters for the uncertainty analysis of rock engineering. Finally，the analysis of practical engineering computation and relative comparison to other methods shows that the proposed method is reasonable.

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MECHANISM ANALYSIS OF SLOPE REINFORCEMENT WITH DEEPLY BURIED PILES WITH MODEL TEST

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2007, 26 (07): -1347 doi:
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To study the mechanism of deeply buried piles stabilizing the slope，a series of large-scale model tests are carried out. Several testing tools including rigid load cells are employed to measure the anti-sliding forces initiated by the piles and the sliding force exerted by the piles，especially the earth pressure cells are used to measure the variation of stress condition at the rear of the back of piles and upward to the top of piles as the sliding force impelled by the system of force output. On the basis of the variation process of measured data，the time and the location of slide surface in the slope are identified；and the maximal anti-sliding forces upward to the top of piles are calculated. Then，the failure modes and transformation were analyzed as the anti-sliding length of the piles changed. Physical conditions of the pile cross-section are determined；and the sliding force subjected to the piles was estimated. The mechanism of deeply buried piles for the slope reinforcement and the relationship between the sliding forces subjected to the piles and that supplied by the slope upward to the top of piles are analyzed to supply scientific basis for the design method of the deeply buried piles.

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LARGE-DEFORMATION DESCRIPTION METHOD FOR CONSTITUTIVE RELATION BASED ON COMPRESSION TEST

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2007, 26 (07): -1356 doi:
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Based on the large-deformation theory of continuum mechanics，a novel method for describing the large-deformation constitutive relations of geomaterials based on compression test was proposed using total Lagrangian description technique. According to the characteristics of compression test，the transformation formulae of stress tensors and strain tensors between the large-deformation method and the corresponding small- deformation method were firstly derived；and the large-deformation constitutive relation(LDCR) of compression was presented with a general meaning. Then the LDCR equation for the case of a small-deformation hyperbolic model，as well as its corresponding simplified large-deformation hyperbolic model，are obtained. The results of case studies and a parametric analysis show that the proposed large-deformation hyperbolic model can well simulate the constitutive-relations of geomaterials under the large-deformation compression condition. From the viewpoint of both the physical definition and the numerical magnitude，the parameters of hyperbolic models for the large-deformation method and the small-deformation method are different but regularly obey a certain function of variation.

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EXPERIMENTAL STUDY ON EARTHQUAKE TREMOR FOR TRANSMITTING LAW OF ROCKBURST IN GEOMATERIALS

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2007, 26 (07): -1365 doi:
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The transmitting and attenuation laws of stress wave in rocks are important and hot research issues in geotechnical engineering and mining engineering. The major reason that roadway or working face is destroyed by rockburst is also the transmitting wave of earthquake tremor. Using TDS–6 seismic experiment instrument，the experiment on the transmitting law of earthquake tremor is carried out for different rocks；and energy attenuation curve is achieved with analyzing the different above-mentioned curves. Experimental results reveal that shock energy attenuates exponentially with the distance from the explosive center. The energy attenuation index h is considerably small in intensified rock and soil media，but much larger in weak or soft media apparently. The energy attenuates quickly in the beginning，and it will disappear after certain distances. These conclusions provide the theoretical basis for studying the failure mechanism of roadway surrounding rock subjected to rockburst and forming the control principle of strong-soft-strong structure for roadway to prevent rockburst.

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NONLINEAR DYNAMIC STUDY ON GAS FLOW IN BROKEN ROCK MASS

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2007, 26 (07): -1372 doi:
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In fields of coal mining，geotechnical engineering，the flow in broken rock is nonlinear，instable and time-varying for seepage parameters. Under the external disturbance，the gradual variation of the seepage parameter is apt to result in the catastrophe of the dynamic responses of the flow system and induces disasters such as water inrush and gas outburst. The study of the flow stability on the broken rock mass induced by mining is a basic subject of a series of important research topics such as controlling the stability of the surrounding rock，preventing the outburst disaster，exploiting and using the underground resources. The theories of bifurcation and catastrophe in nonlinear science are used to study the dynamic mechanism of instability of gas flow in broken rock. The nonlinear dynamical equations of one-dimensional non-Darcy and unsteady gas flow in broken rock are established. The solution diagram of dimensionless velocity under steady-state is given and the distribution laws along the direction of flow are obtained for the pore pressure and the steady-state flow velocity；namely，along the flow direction，the product of the pore pressure and the flow velocity of the dimensionless steady-states is a constant and the square of the pore pressure descends linearly. With low relaxation iteration，the dynamical responses corresponding to the different flow parameters of seepage system are also given. The results indicate that there is a saddle-node bifurcation in dynamic system of flow in broken rock；and at the bifurcation point，the breaking of edges and corners of rock grains is remarkable；thus an arbitrary weak perturbing at this point may result in a fold catastrophe of flow system and induce some dynamic disasters such as gas outburst，etc..

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EXPERIMENTAL STUDY ON CREEP PROPERTIES OF SOFT ROCK UNDER TRIAXIAL COMPRESSION

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2007, 26 (07): -1381 doi:
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With the author-developed gravitation loading style rock creep test machine，under the conditions of constant temperature and constant humidity，triaxial compression creep experiments are conducted under different stress states. Oiliness mudstone samples are taken from Longkou Coalfields. The effects of confining pressure and creep parameters of soft rock were focused on；and other time-dependent behaviors were analyzed. The experimental results show that the stress threshold for the oil mudstone increases linearly with the confining pressure. The ultimate strength of creep is in direct proportion to confining pressure. The creep process of oil mudstone only goes through two phases，that is，one is in the damped creep phase when axial stress is less than the creep ultimate stress；and the other phase is accelerated when axial stress is larger than the creep ultimate stress. The even creep phase of oil mudstone is not observed in the test. The creep viscosity coefficient is become much smaller，which reveals the characteristics of large creep deformation. It is seen approximately as a linear function relation with the latter，but the viscosity coefficient increases slowly with the confining pressure. At the same time，the restriction of lower confining pressure to creep deformation is weaker.

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STUDY ON COMPARATIVE ANALYSIS OF GROUND TEMPERATURE DISTRIBUTION OF BEILU RIVER TEST SECTION IN QINGHAI—TIBET RAILWAY

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2007, 26 (07): -1386 doi:
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Considering the phase-change and influence of the global temperature rising，the computed simulation of the temperature field of the L-typed retaining wall only in Qinghai—Tibet Railway has been carried out using numerical calculation method. Through establishing finite element model of subgrade temperature field，the suitable boundary condition，the initial condition and the heat computation parameter are selected；and the variation situations of ground temperature during the future 10 years in Beilu River test section are analyzed and they are compared with monitored two-year actual ground temperature. The calculated thawing depth and the measured data are basically consistent. The result shows that the characteristics of ground temperature response lagging to the temperature change. It also displays that the proposed model is reliable. The computed result can be adopted by other engineering practices. Future 10-year computed results indicate that the maximum thawing depth(or permafrost table) is not developed. It is explained that the frozen soil has already formed to a new balance；and permafrost table is stable. This result can be considered for Qinghai—Tibet Railway. It is forecast that the ground will finally be of stable thermal equilibrium condition. It indicates that the kind of flexible L-typed retaining wall applied to permafrost region is acceptable.

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BOUNDING SURFACE ELASTO-VISCOPLASTIC CONSTITUTIVE MODEL FOR RHEOLOGICAL BEHAVIORS OF SOFT CLAYS

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2007, 26 (07): -1393 doi:
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An elasto-viscoplastic constitutive model for creep behaviors of soft clays is developed with the theoretical framework of bounding surface plasticity based on the idea of quasi-preconsolidation and critical state concepts. Several important developments on soil creep modeling are proposed together within the model as follows：(1) the concept of delayed volumetric strain from the Taylor secondary compression law；(2) the idea of viscous flow or over-stress loading function；and (3) the theory of time-dependent bounding surface plasticity. The delayed strain was divided into volumetric creep strain and deviatotic creep strain. The volumetric creep strain rate was directly computed from the Taylor secondary compression law；and deviatotic creep strain rate was derived from volumetric creep strain ratio under the concept of over-stress function. In addition，a variable considering implicitly creeping time is adopted in the model，which is determined through the method introduced by Borja. With the introduction of the bounding surface plasticity，the model was capable of simulating the creep behaviors of both normally consolidated clays and over-consolidated clays. The parameters of this model were fewer than other those of creep models，only one parameter—the coefficient of secondary compression was added. The constitutive model proposed is verified by several test results. The good predictions show the rationality and validity of the proposed model.

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DISCUSSION ON TWO SAFETY FACTORS FOR PROGRESSIVE FAILURE OF SOIL SLOPE

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2007, 26 (07): -1402 doi:
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Slope destroy is a progressive process. During the process of formation of the shear bands，the shear strength parameters have different decay rates. So the margin of safety is different for parameters c and . The different softening characteristics of different soils were analyzed. The softening damage is found in the cohesive soil slope as formation of the shear bands，so the decay rate of cohesive c is more rapid than that of internal friction angle . The dilation and softening are disclosed in the sand soil slope，like the formation of the shear bands. The decay rate of internal friction angle is more rapid than that of cohesive parameter c. According to the different decay rates of parameters ，the modes of in the cohesive soil and in the sand soil were put forward. The different modes in the different soils were discussed to offer some references to relevant studies in geotechnical engineering.

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EXPERIMENTAL STUDY ON GAS PERMEABILITY OF MUNICIPAL SOLID WASTE

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2007, 26 (07): -1408 doi:
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Gas permeability of municipal solid waste(MSW) is an important parameter for the analyses of landfill gas migration. The laboratory measurement of gas permeability was carried out on the MSWs taken from the Qizishan landfill in Suzhou City，China. The measurement was performed with a purposely-designed lysimeter. The influences of void ratio，degree of saturation and MSW composition on gas permeability were investigated. The test results show that the gas permeability of the MSW ranges from 10－8 m2·Pa－1·s－1 to 10－5 m2·Pa－1·s－1，and the corresponding intrinsic permeability is between 10－13 m2 and 10－10 m2. For a given composition and degree of saturation(Sr = 0% or 40%)，gas permeability was found to increase exponentially with void ratio of the MSW. For a given composition and void ratio(e = 2.0)，a bilinear relationship was observed between gas permeability and degree of saturation. The degree of saturation corresponding to the division point(i.e. Sr = 50%) was slightly less than that corresponding to the field capacity of the MSW. When the degree of saturation is greater than the division point，gas permeability decreases exponentially with an increase in the degree of saturation. However，at the low range of degree of saturation(i.e. Sr≤50%)，the influence of Sr on gas permeability is not so significant. When the samples have the same void ratio as well as degree of saturation，it is unexpected to find that the gas permeability of the MSW increases with fill age.

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STUDY ON EFFECTIVE STRESS BASED ON DYNAMIC RESPONSE ANALYSIS METHOD FOR SHIELD TUNNEL

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2007, 26 (07): -1416 doi:
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Partitioned solution procedures could be effectively used to solve Biot¢s equations，which can depict the coupled soil-pore fluid systems. With this method，the existing finite element analysis software could be utilized adequately，while the problem of ill-conditioned matrix，emerging in monolithical approach when the coefficient of permeability of the soil is comparatively small，can be settled successful. The partitioned approaches of Biot¢s equations are all based on the discrete form by finite element method，which will lead to the difficulties when employing them in the redevelopment of existing programs. After comparing the transient heat conduction equation and the pore pressure dissipation equation，a new multi-iteration serial partitioned solution procedure is proposed，in which a certain predicted known value is substituted for the coupled unknown item in pore pressure dissipation equation. With the only one unknown parameter，the nodal pore pressure is left in the equation and could be figured out easily. Subsequently，the solution from the above step is incorporated into the second equation and the other variable，the nodal displacement could be calculated separately. And then，all the load steps could be solved in uncoupled form iteration. With little additional procedures，this method could be easily realized in thermo-structural analysis programme(or independent). This differential equation based method，suitable for two or three-dimensional problems and for static or dynamic problems as well as various element types，is proposed. As demonstrated with numerical examples，this approach could give comparatively precise results and has good computational stability. Subsequently，this approach was applied to the transverse dynamic response analysis of Wuhan Yangtze River Tunnel.

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PRIMARY RESEARCH ON NUMERICAL SIMULATION OF HETEROGENEOUS ROCK FAILURE BASED ON VIRTUAL MULTI- DIMENSIONAL INTERNAL BONDS(VMIB)

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2007, 26 (07): -1426 doi:
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Virtual multi-dimensional internal bonds(VMIB) is a multiscale mechanical model developed from virtual internal bond(VIB). It is deemed that the material particles in microscopic are connected with virtual normal bond and shear bond or with normal bond possessing normal and shear stiffness. The macro-constitutive relation in terms of bond stiffness is derived from the interaction between material particles. Owing to its ability to present the diversity of Poisson ratio，VMIB can be applied to more extensive engineering materials. The heterogeneous material，e.g. rock，is composed of different components. The mechanical property varies with location. In order to model the heterogeneous material，thereafter，to simulate its fracture process，the heterogeneity is primarily incorporated into VMIB. The heterogeneous material is assumed to consist of unit cells in which the virtual bonds are spatially randomly distributed. To represent the heterogeneity，the mechanical property of unit cells is assumed to be randomly distributed，which leads to a heterogeneity property on the integrated material level. However，the bond stiffness in a certain unit cell is assumed to be uniform，which leads to a homogeneity property on the cell level. To examine the performance of the presented method，the fracture process of a specimen subjected to confining stress is simulated. In the case where the rock is treated as a homogeneous solid，a run-through shear fracture is observed and the trace of fracture is regular while in the case that the rock is treated as a heterogeneous solid. Many fractures are observed to simultaneously initiate randomly in different locations；and then propagate and finally coalesce. But the general trend is of shear failure. The simulation results show that the presented method could simulate the fracture processes of heterogeneous rocks and primarily reflect the effect of heterogeneity on the failure behaviors of heterogeneous rocks.

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A SIMPLE METHOD CONSIDERING EFFECTS OF CONFINING PRESSURE ON DYNAMIC SHEAR MODULI AND DAMPING RATIO

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2007, 26 (07): -1432 doi:
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Confining pressure is one of the key factors that affect dynamic soil properties such as low-amplitude shear modulus and damping ratio，normalized modulus reduction and material damping curves，etc.. By analyzing the classical model of dynamic soil properties，predictive equations for estimating low-amplitude shear modulus and damping ratio are presented. Based on the study of M. B. Darendeli，a simple method for calculating normalized shear modulus reduction and damping ratio curves is proposed under certain effective confining pressure from those under referenced confining pressure. According to this method，assuming that the confining pressure has little influence on the shape of the curves；the curves under certain confining pressure can be easily obtained by changing the strain value of the reference curves. The key parameter in this method is deduced with regression analysis of laboratory data collected from various sources. The predicted dynamic shear modulus reduction and damping ratio curves are in excellent agreement with those of the empirical models and test results. Because the strain dependency，the proposed method can be easily combined to the equivalent linear method programs such as DYNEQ for seismic site response analysis. Case study shows that it is reasonable to use effective mean confining pressure dependent soil properties to calculate the surface response spectrum of deep site from rock response spectrum under major earthquake.

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STATIC LAGRANGIAN METHOD FOR ANALYSIS OF CONTINUUM MECHANICAL BEHAVIORS

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2007, 26 (07): -1438 doi:
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STUDY ON APPLICATION OF DISPLACEMENT VECTOR ORIENTATION TREND LINE TO WUSHAOLING TUNNEL

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2007, 26 (07): -1448 doi:
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With the three-dimensional deformation survey system composed of the high accuracy lightwave electronic tachometer combined with reflecting film，the three-dimensional displacements at fault F7 and slate with sandwiched Phyllis section of Silurian have been tested and analyzed in Wushaoling tunnel. Meanwhile，the response characteristics and deformation character of excavated strata of tunnel are presented through three-dimensional deformation revelation that is developed by European scholars. Result shows that the displacement vector orientation trend line at the place，which is 1.0 time of the tunnel diameter or less from working face，can be used to reveal the distribution and change trend of rock mass stiffness at certain region，and it can predict the change trend of soft and hard rocks or unfavorable geological structure at excavated strata. At present time，it is still under its initialization for underground construction engineering，and the information related to displacement is analyzed，which is obtained by exaction with that of the practical geological condition of surrounding rock. With the help of other geological forecast facilities or methods，the geological conditions of the unexcavated ground around cavern can be properly predicted.

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THREE-DIMENSIONAL SIMULATION OF BLAST IN MULTI-LAYER GEOMATERIALS

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2007, 26 (07): -1457 doi:
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It is a very complicated problem to simulate the blasting effects of multi-layer geomaterials. Three- dimensional beam-particle model in the frame of DEM(discrete element method) is used to simulate the blasting effects of multi-layer geomaterials. The media have been discretized by spherical elements；and the elements in contacts are connected by beams. So the media are simplified into compound structure，which is composed of particles and beams. The aggregate of particles had the similar strength to the initial media because of the action of beams. The DEM is employed to simulated movements of particle，and the deformations of beams are calculated by the relative displacements between particles in contact. A strength law of beams is used to verify whether a deformed beam exists or not. The emergence of cracks and formation of fragments can be simulated by removed beams whose deformations meet the strength rule. The matrix-displacement method is used to calculate forces of beams，and the forces of beams are exerted on particles as opposite forces. The results show that the large deformations of geomaterials induced by blast can be simulated well by the particle-beam model than those of finite element method based on the continuous mechanics. The model can realistically reflect the crack generation and extension，and the shivers formation and materials shifting away from matrix. The simulation results are approximately coincident with test results. So，the beam-particle model is a valid method to simulate mechanical behaviors with high loading rate.

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TWO NUMERICAL SOLUTIONS OF PILES SUBJECTED TO LATERALLY PARABOLIC DISTRIBUTED LOADS WITH BIPARAMETER METHOD

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2007, 26 (07): -1463 doi:
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In order to satisfy the requirements of design and calculation of piles subjected to laterally parabolic distributed loads，the finite difference method and the pole system finite element method of elastic foundation are presented and discussed in order to compute the displacements and internal forces by adopting biparameter method of lateral subgrade reaction. The finite difference computing and figure processing of displacements and internal forces of piles are programmed. The example shows that the calculation results obtained by the two numerical methods well coincide each other. After the two parameters of lateral subgrade reaction obtained by trial computations based on the measurements of the testing piles，the design and calculation of the piles subjected to laterally parabolic distributed loads can be conducted effectively and reliably with the two methods. The achieved results can provide some references for similar engineering design.

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STUDY ON BEHAVIORS OF MAOPINGXI HIGH ROCKFILL DAM WITH ASPHALT CONCRETE CORE OF THREE GORGES PROJECT

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2007, 26 (07): -1470 doi:
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Maopingxi high rockfill dam is the accessorial dam of Three Gorges Project(TGP)，which is also the highest rockfill dam with asphalt concrete core in China. The deformation rules of the dam when the water level of TGP reservoir reaches to 135 m are analyzed；and the parameters of filling materials are back analyzed. Based on the parameters of back analysis，the behaviors of core wall and the dam are studied by nonlinear FEM when the water level of TGP reservoir reaches to the elevations of 156，165，172，and 175 m(the planed level)，respectively. Effects of parameters of the asphalt concrete on behaviors of core wall are analyzed. Furthermore，a function of hyperbola combined power is adopted in modeling the curves of long-term triaxial creep test of the asphalt concrete；and creep analysis is performed for the dam. Results show that the displacement in horizontal direction and the maximum principal stress of core wall will increase to a larger extent if the creep effect of asphalt concrete is considered. The study results also show that different water level procedures have small differential effects on the behaviors of core wall；and there is little probability of hydraulic fracture，shear and bend failure to the core wall. These results can be referenced to the plan of water level procedures on the dam；and the behaviors of high rockfill dam with asphalt concrete core under high water head are studied.

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STUDY ON INFLUENCES OF KEY STRATA MOVEMENT ON GAS EMISSIONS OF ADJACENT LAYERS

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2007, 26 (07): -1478 doi:
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The key strata control the process of the overlying strata movement and the dynamic expanding of the mining-induced fracture in coal mining stope，and then it will influence the gas dynamic emission of the adjacent layers in the mining-induced fractured rock mass. Based on the in-situ data of two fully-mechanized top-coal caving faces in different overlaying strata in Yangquan Coal Mines，the influences of key strata movement on the gas dynamic emission of the adjacent-layers are comparatively studied. The results show that the dynamic processes of the gas emission of the adjacent-layers in the different overlaying key strata are different，which has further verified the dynamic control of the key strata on the gas emission of the adjacent layers. The applicability of the gas extraction way of the adjacent layers in different overlaying key strata at the initial mining stage is also analyzed. It is put forward that，in order to improve the gas extraction efficiency，the actual overlaying key strata should be considered before the decision of the gas extraction way of the adjacent layers at the initial mining stage.

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STUDY ON DISCONTINUOUS MEDIUM MODEL FOR UNSATURATED HYDRO-MECHANICAL COUPLING OF FRACTURED ROCK MASSES

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2007, 26 (07): -1485 doi:
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[PDF 442 KB] (1300)

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The characteristics of fluid flow in fractured rock masses are more complex than general porous medium flow in virtue of randomness，fuzziness of mechanical parameters and corresponding complex geomechanical environment. However，geotechnical engineering design，performance and safety assessment are often involved in fluid flow and hydro-mechanical coupling of fractured rock masses，making hydro-mechanical coupling of fractured rock masses being hot in mechanical investigation. In recent years，some advancements are achieved in saturated hydro-mechanical coupling，but saturated flow cannot be adopted simply in many practical projects. Therefore，most important influences of unsaturated hydro-mechanical coupling in fractured rock mass on strength and stability of the rock projects should be considered. Investigating productions for hydro-mechanical coupling of fractured rock masses by a good many scholars were generalized；and unsaturated hydro-mechanical coupling analysis model based on discontinuous medium method was put forward according to the mechanical calculation theory of discontinuous deformation analysis(DDA) and unsaturated fluid flow analysis. Taking reservoir rock slope as an example，the stability of rock slope was discussed with rainfall. The results indicate that rock slope stability is greatly reduced with increase of infiltration time of rainfall. The greater rainfall intensity is，the more greatly the stability coefficient of rock slope is reduced. Especially，the stability of the rock slope with/without considering coupling was different：the greater rainfall intensity was，the greater difference between two cases was. The calculation results achieved by numerical simulation and practical projects application agree well with those of in-situ tests，which illuminates that hydro-mechanical coupling model could reflect hydraulic characteristics of fractured rock masses. It is proven that the numerical model is feasible and valid in practical projects.

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CORROSION EVALUATION FOR EXISTING GROUND ANCHORED STRUCTURE

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2007, 26 (07): -1492 doi:
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The ground anchored structures are widely used for almost tens years in China；and the anchored structures are vulnerable to failure by corrosion in the metal elements. It will cause injury or loss of life，significant economic loss，and large rehabilitation costs. Therefore，people pay more attention to how to evaluate the corrosion of ground anchored structure. By analyzing the influential factors of corrosion of ground anchored structure and drawing the theory of matter element analysis(MEA) into analytic hierarchy process(AHP)，a multi-level assessment model and an evaluation method to estimate the corrosion of the existing ground anchored structures are constructed. The initial weights and the index system used in the model are established. The changeable weight is adopted. The AHP model for the fixed length(free length) has 17 indexes；and the AHP model for anchor head has 5 indexes. Meanwhile，the criteria for the index system are given. Finally，the corrosion evaluation procedures are presented by an example which is a part of demonstration project in Chongqing—Guizhou Highway.

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VARIATION OF UNSATURATED SOIL STRENGTH WITH WATER CONTENTS

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2007, 26 (07): -1499 doi:
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The variation of the strength of unsaturated soil with water contents is studied；and the practical strength formula is developed. To study the relationship between the strength and the water content，it is necessary to keep the water content constant in the test. The pore air pressure dissipates quickly and the pore water pressure does not have such behavior. To study the problem，it is necessary to guarantee that the pore air pressure has dissipated completely in the test，and to adjust the general triaxial test apparatus to strength tests of unsaturated soil. The test procedure and control measures to realize the above two test aims are put forward. Secondly，based on the test results，the influences of water contents on strength are analyzed. It can be easily found that the cohesion and the angle of internal friction of unsaturated soil decrease linearly with the increase of water content. Then，the total stress strength formula of unsaturated soil is established. If the water content distribution of soil strata is known，the strength can be easily obtained by the presented formula，i.e. the difficulty of measuring and calculating suction pressure can be avoided. For the water content can be easily obtained，the presented formula is convenient and practical.

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ANALYSIS OF SLIDING FAILURE MECHANISM AND TREATMENT FOR TAIHUA HIGHWAY EMBANKMENT SLOPE OVER SOFT SOILS

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2007, 26 (07): -1504 doi:
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[PDF 331 KB] (1216)

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Numerical method combined with field investigation is employed to explore the sliding failure mechanism of Taihua highway embankment during construction，which is built on soft soils and the soft soils are improved with stone columns. The analytical results show that the original design using stone columns to improve soft soils is not acceptable because the undrained shear strength of the soft soils is too low to confine the stone columns efficiently. As a result，no completed stone columns are formed in the soft soils，with which the high rate of embankment filling causes the sliding failure of the embankment slope. In addition，a treatment method by using rigid concrete tube-pile is presented. For the compression stiffness of pile is greater than those of soft soils，most of the embankment loads are borne by piles，and the remaining load is carried by the soft soils，which allow the embankment to be built in a single stage without further endangering of undrained failure of soft soils and the settlement of embankment can be reduced. Numerical analysis and field monitoring results both demonstrate that the soft soils treated by using rigid concrete tube-pile is successful.

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2007, 26 (07): -1511 doi:
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[PDF 102 KB] (1122)

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2007, 26 (07): -1512 doi:
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[PDF 107 KB] (1110)

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