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2005, 24 (10): -0 doi:
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2005-10期目录

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INSIGHT INTO SOME ASPECTS OF DISCRETE ELEMENT NUMERICAL METHODS FOR ROCK MASS

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2005, 24 (10): -1639 doi:
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Discrete element numerical methods are based on isolated block model of jointed rock mass. In this paper，some typical problems and difficulties of discrete element numerical methods are studied so as to obtain clearer and deeper understanding to them. The problems and difficulties are associated with various algorithms of discrete element numerical methods and their peculiarities，deformation，overlap between blocks，contact detection(including that of three-dimensional problems)and equation solving(especially the inherent relation between the single-block-equation solving and the whole-equation solving). Some helpful and meaningful results are obtained.

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FRACTURE MODEL OF JOINTED ROCK MASS SUBJECTED TO SEISMIC LOADING

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2005, 24 (10): -1645 doi:
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A fracture model of jointed rock mass is established considering the effect of horizontal seismic acceleration. Based on the proposed model，the relationship between the stress intensity factor，and length，spacing and dip of joints is discussed. The analytical results show that the stress intensity factor is significantly dependent on the joint dip when subjected to the horizontal acceleration. When the joint dip is increasing，the rock mass becomes more likely to be fractured. Moreover，with the increasing of the joint dip，the dominant fracture mechanism will change from the sliding type to the tensile type. The effect of the joint length on the fracture is also significant. The bigger the joint length is，the more likely the rock mass is to be fractured if the ratio of the joint spacing to the joint length is moderate. If the ratio of the joint spacing to the joint length is too big or too small，the proposed model will be invalid. The proposed model is practically valuable for the safety analysis of rock mass subjected to seismic loading.

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3D DISCRETE ELEMENT METHOD BASED ON DIRECT METHOD OF JOINT NETWORK SIMULATION

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2005, 24 (10): -1649 doi:
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A practical method is put forward based on the direct method of joint network simulation combined with 3D discrete element program 3DEC to solve the problems of failure of structurally controlled engineering rock masses. Failure is controlled to a great extent by the presence of discontinuities in shallow excavations in hard rock，so a correct interpretation of the significant discontinuity sets is significant for analyzing stability of these excavations. The direct method of joint network simulation is efficient to identify the blocks of rock masses. It can be carried out through FISH language embedded within 3DEC. An example is presented to illustrate this procedure and the results.

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FLUIDIZATION MECHANISMS AND MOTION SIMULATION ON FLOWSLIDES TRIGGERED BY EARTHQUAKE AND RAINFALL

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2005, 24 (10): -1654 doi:
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The difference between the fluidization mechanisms of the Tsukidate flowslide triggered by earthquake and the Yamashina flowslides induced by rainfall was examined through field investigations，soil tests and numerical simulations. In the case of the Tsukidate flowslide，after a liquefaction of sliding mass，the combination effect of grain crushing and rapid shearing rate of the pyroclastic material on the excess pore pressure generation was concluded as the main reason. While，in the case of the Yamashina flowslides，the low shear strength mobilized in the fully saturated weathered mudstone debris with a very low permeability was attributed to the high mobility of the flowslides.

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STUDY ON DEFORMATION MODULUS OF ROCK MASS IN WORKING STRESS STATE

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2005, 24 (10): -1662 doi:
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The parameter values of rock mass have a direct bearing on its confining pressure. The parameter values applied in the design of a project should reflect the situation of the project in working stress state. The formula of confining pressure expressed in initial in-situ stress of in-situ test samples and the formula of surrounding rock pressure confining pressure in working stress state are established based on the example of deducing the deformation moduli of foundation rock mass of the high arch dam of the Hydropower Station No.2 on the Yellow River in working state from in-situ test results. The relationship between in-situ test results and confining pressure is established. The calculation results of the example are reasonable，which proves that the proposed method can be used in design.

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NUMERICAL SIMULATION OF COUPLED GAS FLOW IN FAILURE PROCESS OF GASSY COAL-ROCK

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2005, 24 (10): -1667 doi:
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Based on the basic theory of coal-rock deformation and gas flow in coal and rock formations，considering the heterogeneity of the coal-rock，the nonlinear variation characteristics of gas permeability，and the coupled fluid-solid interaction between gas flow and solid deformation during the coal-rock deformation and failure process，a numerical model(RFPA2D–Flow) on coupled gas flow in coal-rock formations during the failure process of gassy coal-rock is established；and the numerical solution method for the model is also presented. Then，using the RFPA2D–Flow code，the catastrophic delay outburst of coal and gas induced by cross-cutting underground coal mine is numerically modeled to investigate the mechanism of coal and gas outbursts. The numerical simulations reproduce the whole process of the initiation，propagation，interaction，coalescence of the microcracks under the combined action of gas pressure，in-situ stress，and physical and mechanical properties of coal-rock. It is indicated that delay outbursts together with instantaneous outbursts are both caused by combined action of gas pressure，in-situ stress and physical and mechanical properties of coal-rock；and the outbursts process can be subdivided into four phases，namely，stress concentration stage，coal-rock fracturing and splitting induced by the combinations of gas pressure and in-situ stress，cracks propagation driven by gas pressure and the abrupt ejection of coal and gas. And so，it offers some theoretical basis and evidence to further investigate the mechanisms of gas drainage to prevent the occurrence of coal and gas outbursts in underground collieries.

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ANALYSIS OF EFFECTIVE STRESS IN ADSORBED METHANE-COAL SYSTEM

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2005, 24 (10): -1674 doi:
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Most of gas (methane) in coal seam is in adsorbed state. At present，the attention of researchers is attracted to the relationship of the mutual action between the solid coal and the adsorbed methane because it is closely connected with the prevention and control of the burst of coal and gas in mining and the exploitation of methane. Terzaghi¢s effective stress formula can not be adapted in the calculation of the effective stress in adsorbed methane-coal system. Therefore，based on principles of surface physicochemistry and elastic mechanics，the calculation formulas on the swelling deformation of adsorption，the swelling stress of adsorption，and the effective stress in the adsorbed methane-coal system are derived. The computation solution of theory is essentially accordant with the experimental solution. The test and analysis show that the mechanical effect of the free gas pressure in pore is less important to coal seam because the porosity of coal is smaller than the porosity of soil by an order of magnitude，and that the changing law between the swelling strain of adsorption and the swelling stress of adsorption agrees with the Hooke¢s law because micropore-containing solid matrix of coal grains is separated by crevices discontinuously；and the swelling deformations of contact points of coal grains under constraint condition are similar to that in uniaxial compression

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NUMERICAL STUDY ON COALBED METHANE TRANSIENT SEEPAGE FLOW WITH MULTI-WELLS

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2005, 24 (10): -1677 doi:
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A new coalbed methane transient seepage flow model with multi-wells is developed by considering the wellbore storage and skin effect. The problem is solved for the different outer boundaries，such as the circular，the rectangular and the arbitrary quadrilateral boundaries，coalbed boundaries with varied sinks and sources in the calculation region. The pressure distributions are obtained at different times in the model regions. From the pressure propagation process，it shows that the shape and properties of boundaries do not affect the pressure propagation in the early stage；and the sinks and sources strongly affect the pressure propagation before the pressure wave meets any kind of boundaries. The results also show that there is no pressure contour line between two sinks，which means that there is a streamline as a closed boundary does. For two sources，there must be a pressure contour line between them，which means that there is a streamline as a constant pressure boundary does. All these results supply fundamental theories to the reasonable development of coalbed reservoir.

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EQUATION FOR HORIZONTAL-RADIAL DISPLACEMENT OF AQUIFER CAUSED BY WATER-PUMPING/INJECTION

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2005, 24 (10): -1687 doi:
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The displacement equation for horizontal axisymmetric deformation of aquifer，as a homogeneous and isotropic porous medium，is developed under assumptions that matrix material is perfectly elastic，that skeletal particles and water are homogeneous and are not compressible，and that changes of pore pressure in the aquifer lead only to horizontal displacements of the solid skeleton of the formation with constant vertical mechanical loading，but not to vertical displacements. Compared with the corresponding equations developed under traditional assumptions (Jacob assumptions)，the new equations have the same structural form but with a different coefficient. The new-defined displacement coefficient，though still constant，is greater than traditional one. The new equation should be distinguished from the traditional one unless the coefficients in them are obtained by field tests in the fields or model calibration. The calculation value of vertical compaction will be bigger than its actual value if the skeletal elastic water storage in the subsidence model is obtained from pumping test.

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STUDY ON PERMEABILITY OF FOUNDATION SOIL OF BRIDGES ON LOWER REACHES OF YANGTZE RIVER

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2005, 24 (10): -1692 doi:
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The importance to monitor the pore water pressure and to study the permeability of soil under the north anchorage of Jiangyin Yangtze River Highway Bridge is analyzed firstly. According to the observed data，the hydraulic connection characteristics of pore water and river water are analyzed. Then，based on Biot′s consolidation theory，the permeability coefficient of the foundation soil under the north anchorage is obtained by back analysis and varying-scale optimization method. It shows that the permeability coefficient of the soil under the anchorage is 23 percent of the original value. Finally，the rationality of the parameter is verified by comparison btween the straight analysis results and the observed displacement. Parameters of soil will change with the stress condition. Load of huge foundation will affect the permeability of soil. The reduction of permeability of soil is beneficial to the stability of foundation soil.

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STUDY ON MECHANICAL AND HYDRAULIC BEHAVIOR OF TUNNEL SURROUNDING ROCK MASSES IN EXCAVATION-DISTURBED ZONE

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2005, 24 (10): -1697 doi:
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The damage of tunnel surrounding rock masses usually results from the redistribution of stress in disturbed rock mass in tunnel excavation process. The excavation-disturbed zone (EDZ) is defined as the rock zone where the rock properties and conditions，such as fracture，stress and hydraulic aperture，have been changed due to the processes induced by excavation. EDZ is considered to be physically less stable and can form a continuous and highly permeable pathway of groundwater flow. The characterization of EDZ will affect tunnel support structure design，tunnel construction and tunnel surrounding rock mass stability analysis. Seismic survey techniques can be used to examine the nature of EDZ around the tunnel. Based on the concept of EDZ and the primary factors that lead to the change of rock properties，a methodology is proposed to depict mechanical and hydraulic behavior of EDZ. By using the in-situ data，deformability and hydraulic properties are studied by numerical analysis. The results show that the excavation damage depends on the excavation method. In addition，the influence boundary of the excavation-disturbed stress zone is smaller than that of the seepage. Therefore，the seepage boundary condition should be emphasized in establishing the coupled fluid-solid numerical models. The results will make the establishment of coupled fluid-solid model more reasonable.

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ANALYSIS AND PREDICTION OF VAULT CROWN SETTLEMENT IN METRO TUNNELING AT SHALLOW DEPTH

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2005, 24 (10): -1703 doi:
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Due to lag of settlement monitoring，measured vault crown settlement is merely a portion of total settlement in construction of city metro tunnel，and ratio of measured settlement to total settlement varies notably with ground condition. Therefore，the vault crown subsiding process and its total settlement are important factors for tunnel supporting design and environment controlling. Regression analysis is carried out on vault crown settlement in some section tunnels of First Stage of Shenzhen Metro，which shows that vault crown settlement process keeps to an exponential function，so the unmeasured vault crown settlement can be predicted. The reliability of regression analysis is validated through numerical simulation；and the larger pre-settlement of vault crown is achieved ahead of heading face. Then，the relation between vault crown settlement and ground settlement is analyzed considering the release of stratum stress during tunnel excavation and stratum water-loss effect caused by the flowing out of underground water；and in this way，the complicated relation of settlements in tunneling of First Stage of Shenzhen Metro may be explained. The complicated relation of settlements is related to the lag of monitoring and water and sand in stratum. The conclusion is significant for the excavation，supporting and environment controlling of city metro tunnels.

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SIMULATION OF DEFORMATION AND FAILURE OF SURROUNDING ROCK MASSES OF UNDERGROUND CAVERN IN LOW GROUND STRESS REGIONS WITH FINITE ELEMENT METHOD

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2005, 24 (10): -1708 doi:
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The low ground stress state has great influence on the features of deformation，failure and stability of rock masses in such stress state. In this paper，2D elastoplastic finite element method(FEM)is used to simulate the whole deformation and failure process of surrounding rock masses of the underground cavern project of Heihe River Reservoir in Xi′an city. The rock masses are in the low ground stress regions and belong to class Ⅳ according the code of rock mass quality classification. The established computational model consists of 5 kinds of stratum elements. According to the stress distribution characteristics in the low ground stress regions，the boundary conditions of the computational model are determined. The FEM software 2D- is used to conduct the numerical simulation. The adopted physical and mechanical material parameters are obtained by tests. The characteristics of whole process of surrounding rock mass deformation and failure have been simulated. The simulation results show that the deformation and failure will be formed at the vault and both sides of underground cavern；and the deformation and failure of surrounding rock masses at the vault are more serious than those at both sides. These results agree well with the real cases. The achieved results will be of great significance for the further study of deformation and failure mechanism of surrounding rock masses and ensuring the construction progress.

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STUDY ON DESIGN AND CONSTRUCTION OF MAIN STRUCTURE OF LIGHT RAIL UNDERGROUND STATION

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2005, 24 (10): -1715 doi:
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At Linjiangmen station of Chongqing Light Rail Project，the excavation width of the main structure is 23.040 m，and the height is 50.578 m. But the smalless thickness of cover rock masses is only 10.5 m. It is a super-shallow-berried single-span tunnel project. The New Austrian Tunneling Method is used in design of station，constant-section composite lining is employed for the station structure；and the construction technique of double-side-drift buried excavation is adopted. The structure design and construction scheme are studied，in which the geologic condition，main structure and construction difficulty are expounded.

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DETECTING DEPTH OF RELAXATION ZONE OF TUNNEL SURROUNDING ROCK BY USING LANDSONAR ON SURFACE OF ROCK OR LINING

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2005, 24 (10): -1722 doi:
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Landsonar method，is a new survey method that has been successfully used in shallow layer survey and geological prediction of condition before of tunnel working face. It can be used to detect the depth of relaxation zone of surrounding rock of a tunnel with a wave source induced by hammering on the surface of rock or lining. The results by landsonar method and acoustic wave measurement method with boreholes are compared，which shows that they are consistent. In the detection of the depth of relaxation zone of surrounding rock by landsonar method，the geophones are set near by the wave source point. The measuring stations are arranged in a measuring line of 2-4 m long with a distance of 20-30 cm to one another. The data of all stations in a line are treated to a time-section on that the reflection image of the boundary line of relaxation zone can be clearly differentiated. Wave velocity can be measured by refracted wave method or common center point method on surface of rock mass or lining；and the depth of the boundary line of the relaxation zone can be calculated. Landsonar is more time-saving and convenient because it does not need boreholes which are needed in acoustic wave measurement method.

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GROUTING TECHNIQUE FOR HIGH-PRESSURE AND WATER-RICH AREA IN MAOBA SYNCLINE AT YUANLIANGSHAN TUNNEL

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2005, 24 (10): -1728 doi:
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The geologic condition of the high-pressure and water-rich area in Maoba syncline at Yuanliangshan tunnel of Chongqing—Huaihua Railway is complex and regarded as a for bitten area of tunnel construction. The karst development characteristics of this area is systematically introduced；and the geologic and karst structure is classified. The distribution and shape of karst caves and the filling in them are investigated by the advanced investigation means，and reliable forecast is made accordingly. Based on analysis of structure and intensity of the filling，the reasonable grouting materials and grouting technology are determined. Pre-grouting，radial grouting in surrounding rock and reinforcing grouting behind lining are implemented respectively according to the geologic condition；and inspecting method and estimating method of grouting effect are also brought forward to ensure the grouting reliability. Satisfying results are achieved；and safety of tunnel construction is ensured through adopting these measures. The results can provide references to tunnel construction in karst region.

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ANALYSIS OF PLASTIC DEFORMATION AND FRACTURE ENERGY OF ROCK SPECIMEN IN UNIAXIAL COMPRESSION

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2005, 24 (10): -1735 doi:
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Firstly，axial plastic deformation of rock specimen in uniaxial compression subjected to shear failure is investigated. Assumption is made that shear localization in the form of a single shear band is initiated at peak shear stress in shear plane and that axial plastic deformation stems from the plastic shear slip of shear band. Relative shear displacement along shear band depends on shear stress level and shear band thickness described by gradient-dependent plasticity. The relative displacement can be decomposed into axial and lateral parts. The former is equal to axial plastic compressive deformation at rock specimen end. Then，relation between the axial plastic deformation and the flow compressive stress is proposed. It is found that shear band inclination angle influences the slope of the relation curve. If the angle is not dependent on specimen length，then the relation curve is not a strict straight line；but a narrow zone like a horsetail. In fact，the influence of shear band inclination angle can be neglected so that the slope can be approximately regarded as a constant，as is in agreement with some experimental results. Secondly，the effect of specimen length on total fracture energy in uniaxial compression subjected to shear failure is analyzed. Total fracture energy is the sum of pre-peak fracture energy and post-peak fracture energy. In pre-peak stage，Scott model is used to describe the nonlinear elastic stress-strain relation and analytical solution of pre-peak fracture energy is derived. The solution shows that the pre-peak fracture energy is related to specimen length. In strain-softening stage，linear strain-softening constitutive relation between shear stress and plastic shear strain is adopted. Analytical solution of post-peak fracture energy dissipated by localized plastic shear deformation is derived based on gradient-dependent plasticity. The reasonability of present analytical solution of total fracture energy for quasi-brittle materials is verified by linear regression on earlier experimental result. Longer length of specimen leads to higher total fracture energy，and bigger elastic modulus to lower the total fracture energy. If the size effects of compressive strength and inclination angle of shear band are neglected，the reason for size effect of total fracture energy is the uniform plastic compressive deformation in pre-peak stage.

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MECHANICAL PROPERTY AND FAILURE CRITERION OF CONCRETE UNDER BIAXIAL TENSION AND COMPRESSION AFTER FREEZE-THAW CYCLING

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2005, 24 (10): -1740 doi:
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Most concrete structure buildings and dams in northern cold region are in complex stress state，and the freeze-thaw cycling has adverse effect on the mechanical properties of concrete. Biaxial concrete tension- compression tests of 4 different stress ratios，0，－0.05，－0.15 and －0.25 after 0，25，50 and 75 freeze-thaw cycles are carried out respectively using the concrete static-dynamic triaxial test system in the State Key laboratory of Coastal and Offshore Engineering，Dalian University of Technology. The strain of two loading directions and the strength of concrete are measured. The strength and the deformation of concrete under different tension-compression stress ratios are studied based on the experiments；and the results indicate that the compressive strength and the tensile strength are decreased with the increasing of freeze-thaw cycles；and that the effect of tension-compression stress ratio on strength and deformation of concrete after freeze-thaw cycling is significant. Failure criterion of concrete under biaxial tension and compression is established in normal stress space and octahedral stress space. The results show that in practical cases，resistance capability against freeze-thaw cycling of concrete structure under biaxial tension and compression is inferior to that of concrete structure under uniaxial stress；and more attention should be paid to this point in structure design.

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RESEARCH ON DYNAMIC RESPONSE LAWS OF LINING STRUCTURE OF TUNNELS BASED ON WAVELET ANALYSIS

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2005, 24 (10): -1746 doi:
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A method of wavelet analysis with the dynamic FEM of lining structure of tunnels and a viscoelastic boundary condition are expounded. The spring-damper element is adopted to simulate the viscoelastic boundary condition. And then，a corresponding FEM model is established. Based on the results of in-situ vibration measurement，the dynamic properties of Zhuting Tunnel on the Beijing—Guangzhou Line are analyzed under the vibrating loadings of the speed-up train. The time-response laws of vibration displacements，accelerations，bending moments，axial forces and shear forces of characteristic spots on the lining structure，are obtained. Comparing the calculation results with the in-situ data shows that the proposed method is reasonable. The results are significant for the analysis of structure stability of tunnel with speed-up trains passing through.

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NEW PREDICTION MODEL FOR DAM DEFORMATION BASED ON DECOUPLED WAVELET AND OPTIMAL NEURAL NETWORKS

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2005, 24 (10): -1751 doi:
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The three-stage strategy，proposed by Murtagh，for complicated time series prediction with wavelet and neural networks is improved. Based on the improved strategy，a new prediction model of decoupled wavelet and optimal neural network is proposed to increase the ability of neural networks for dam deformation prediction. Firstly，a new space reconstruction technique based on the main peak reconstruction of energy spectrum of original data is developed using the quasi-wavelet-packet property of redundant Haar wavelet；and then，it is used to substitute for the first stage of the three-stage strategy to built a better neural networks operating platform. Secondly，the optimal-refreshing window technique for neural network self-optimization is developed by using the optimal brain surgeon technique to prune the networks coefficients，and the inner condition of the neural network is optimized by substituting it for the second stage of the three-stage strategy. The adaptability and the analyzing ability of the newly reformed model are increased for the prediction of complicated dynamic system．It is proved by many evaluating indices such as relative mean square error，cross-relation，normal mean square error and direction symmetry in a case of predicting dam deformation that its function is significantly improved as compared with that of the three-stage strategy.

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EXPERIMENTAL STUDY ON EFFECT OF SURFACE WATER ON BEARING CAPACITY OF PILE FOUNDATION IN LOESS AREA

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2005, 24 (10): -1758 doi:
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The special engineering feature of loess leads to the collapsible deformation of the pile foundation when the soil around piles is saturated. The deformation usually leads to negative friction and reduces bearing capacity of piles. Based on the loading test before and after saturation of pile foundation of Shaanxi Zhichuanhe Bridge，the bearing capacities before and after saturation are analyzed. It is found out that effect of surface water on the property of bearing capacity of pile foundation in loess area is significant. The regularity of settlement of pile foundation and soil around is summarized. The results can provide references to the design and construction of pile foundation in loess area.

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TWO-DIMENSIONAL NONLINEAR FINITE ELEMENT ANALYSIS OF SINGLE DIAPHRAGM WALL

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2005, 24 (10): -1766 doi:
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Single diaphragm wall is one of excavation supporting structures that are greatly recommended in Guangzhou Metro Project. Compared with the supporting structure of circular cast-in-place piles，it has many advantages in structure. In this paper，a method is put forward in which straight beam element is employed to simulate the supporting wall and a kind of rotational Goodman interface element is employed to simulate the behavior of interface between the soil and the supporting wall. The method of calculation and the stiffness matrix of the elements for the supporting wall and the interface elements are analyzed with 2D FEM. In the Ergong Station excavation of single diaphragm wall of Guangzhou Metro Project，the analysis involves the distribution of displacements and bending moments of supporting structure，the settlement of ambient soil and the distributions of the plastic zones and principal stresses. The calculation results are compared with those measured in-situ，and show that they match with the latter very well.

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DISCUSSION ON SETTLEMENT CALCULATION OF EMBANKMENT CONSIDERING LATERAL DILATION BEHAVIOR OF SOILS

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2005, 24 (10): -1772 doi:
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Soil lateral dilation is one of the important factors causing foundation settlement，but the results of one- dimensional layer-wise summation method(LSM) can not consider lateral deformation because it is based on the uniaxial compression test with lateral deformation being completely confined. In order to improve the settlement calculation accuracy of highway embankment on soft ground，the modified formulae which combine with height of embankment and void ratio of common clay and soft clay in roadbed are put forward according to nonlinear FEM analyses，which are applicable to uniform or nonuniform roadbeds. Examples prove that，with this method，one-dimensional methods can consider soil lateral deformation and their results are much close to the measurements；so these formulae are of significance in practical projects.

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FRACTURING BEHAVIORS OF CEMENTED SOIL UNDER ENVIRONMENTAL EROSION

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2005, 24 (10): -1778 doi:
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An experiment on fracturing process of cemented soil is conducted to investigate the behaviors of cemented soil under various environmental conditions. The fracturing process of cemented soil is observed in real time using high-precision numeral camera. The surface effects of cemented soil are studied under different ionic strengths，values of pH and chemical solutions. The fracturing behaviors of cemented soil under environmental erosion are analyzed. At the same time，mechanisms of erosion are explained. The results show that environmental erosion has little effects on fracturing process in contrast to evident influence on mechanical strength.

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TESTING STUDY ON DYNAMIC PROPERTIES OF EXPANSIVE SOIL AND IMPROVED EXPANSIVE SOIL

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2005, 24 (10): -1783 doi:
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Based on the improving tests of expansive soil roadbed of Chengdu Bypass Expressway，permanent deformation and dynamic properties of expansive soil and improved expansive soil under repeated loading are studied using dynamic triaxial test. Under the different confining pressures，the relationships among elastic strain，cumulative plastic strain，dynamic strain and the number of loading repetition are analyzed respectively. The three stages of cumulative plastic strain of expansive soil are easier to distinguish from log-log coordinate system than from common coordinate system. The log-log relationship between the cumulative plastic strain and the number of loading repetition is approximately linear when ignore the primary stage and the tertiary stage of material deformation. There is similar relationship between dynamic strain of expansive soil and the number of loading repetition. The dynamic properties，such as dynamic elastic modulus，dynamic cohesion，dynamic friction angle，damping ratio，of expansive soil and improved expansive soil are compared. The results show that the engineering characteristics and strength parameters of improved expansive soil are significantly improved.

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STUDY ON FRACTAL GRADATION OF TAILINGS AND KNOWLEDGE BANK OF ITS CEMENTING STRENGTH

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2005, 24 (10): -1789 doi:
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Characteristics of tailings gradation are studied by using fractal theory. Experimental data about the fractal gradations of tailings material and their cementing strength from a lot of mines are analyzed. Neural network is used to establish the model of knowledge bank which embodies the relations between strengths of cemented tailings and content of cement，consistence，fractal dimension of porosity and correlation coefficient of fractal dimension. Combining grading method with chaotic optimization，the neural network model achieves rapid training and avoids local minimum when there are a lot of samples to be trained. Research results show that the strengths of cemented tailings increase with the decrease of fractal dimension of porosity and with the increase of the correlation coefficients of fractal dimension. Because fractal dimension of porosity and its correlation coefficient embody the global distribution information of tailing granule，they can be used as a standard of rationality of gradation. According to gradation of tailings，the knowledge bank model can predict the strengths of cemented tailings in different contents of cement or consistence，and guide filling design in mine.

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REVIEW ON APPLICATION OF OPTICAL MEASUREMENT METHODS TO EXPERIMENTAL INSPECTION OF ROCK MECHANICS

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2005, 24 (10): -1794 doi:
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The advantages and limitations of optical measurement methods，such as photoelasticity，holography，speckle photography，morie，observation method based on digital image and digital speckle correlation method (DSCM)，are concluded. Based on a discussion on the new trends of experimental inspection of rock mechanics，an inspection system based on DSCM is suggested to be developed for experimental inspection of rock mechanics. The system will help to accomplish some new inspection items and to solve some important problems in rock mechanics.

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APPLICATION OF DIGITAL CONTROL WATER CUTTER TO CUTTING OF NATURAL ROCK MATERIALS

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2005, 24 (10): -1800 doi:
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The principle and system constitution of multifunctional digital control water cutter are investigated. Experimental study is carried out on its applications to the machining of natural rock materials. The device can be widely used to cut various metal and nonmetal materials；and it can actualize special curve cutting which is difficult to machine by other traditional cutting tools. The device is characterized with convenient interactive manipulation，low pump pressure，low specific energy consumption and low cost，which will be widely applied to the cutting of natural rock materials.

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ELASTIC ANALYSIS OF INTERACTION BETWEEN STIFFENED RAFT AND SUBSOIL

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2005, 24 (10): -1804 doi:
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A semi-analytical and semi-numerical method，which makes use of compatible analysis of force and displacement between beams，slab and ground，is developed to analyze interaction between stiffened raft and subsoil by considering the stiffened plate as a composite system of grillage beams and slab. The result converges well and has credible precision. Numerical examples prove that this method has good validity and practicality. Compared with plate raft，stiffened raft has evident advantages in diminishing nonuniform settlement，improving the internal force distribution of raft and reducing construction cost.

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EXPERIMENTAL STUDY ON CONSOLIDATION OF DREDGER FILL SLURRY WITH FLY ASH

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2005, 24 (10): -1811 doi:
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Making land by dredger fill provides a novel idea to solve the problem of lacking economic construction land in coastal area of Southeast China；but it is still a technical question to consolidate dredger fill foundation quickly and economically. Testing study that uses fly ash as additive to treat dredger fill slurry and to consolidate dredger fill foundation is carried out to find an efficient consolidation method. A number of experiments proves that the engineering geological properties of consolidated dredger fill has been improved. With the increase of the quantity of fly ash in dredger fill，the bearing capacity and shear strength of consolidated dredger fill are enhanced；and characteristics of consolidation are improved. There is close relationship between the changes of microstructure characteristics and improvements of engineering geological property. The structure type of consolidated dredger fill changes from flocculent structure to skeleton-flocculent structure，equivalent diameter of structure units becomes bigger，and a part of structure units became granular structure. The changes of microstructure directly lead to improvement of engineering geological property. It can be concluded that treating dredger fill slurry with fly ash is feasible and economical.

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DISCUSSION ON“STABILITY ANALYSIS OF SOIL SLOPE BY FINITE ELEMENT METHOD WITH PALSTIC LIMIT UPPER BOUND”

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2005, 24 (10): -1817 doi:
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REPLY TO DISCUSSION ON“STABILITY ANALYSIS OF SOIL SLOPE BY FINITE ELEMENT METHOD WITH PLASTIC LIMIT UPPER BOUND”

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2005, 24 (10): -1819 doi:
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