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2005, 24 (14): -0 doi:
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2005-14期目录

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STUDY ON RECTIFIED METHOD OF MOHR-COULOMB STRENGTH CRITERION FOR ROCK BASED ON STATISTICAL DAMAGE THEORY

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2005, 24 (14): -2403 doi:
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Firstly，the computation method of the strength of rock micro-unit based on Mohr-Coulomb strength criterion is introduced. A damage constitutive model is established according to the rock triaxial stress-strain test curve and the assumption that the strength of rock micro-unit is of Weibull distribution. The model can reflect the full process of rock failure under specific confining pressure. Then，the model parameters are rectified based on the relation between damage model parameters and confining pressure. A three-dimensional damage constitutive model，which answers to the fact，is established accordingly. Finally，the approach for erecting rock strength criterion is discussed by acquiring extrema using multivariate functions according to the conception of yielding or failure；and the Mohr-Coulomb strength criterion is rationally rectified accordingly. The comparison of the rectified Mohr-Coulomb strength criterion with practical result and the Mohr-Coulomb strength criterion shows that the former has obvious advantages over the latter.

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RESPONSE SPECTRUM ANALYSIS OF GROUND VIBRATION INDUCED BY SINGLE DECK AND MULTI-DECK BLASTING

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2005, 24 (14): -2409 doi:
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The response spectrum that is largely applied in earthquake engineering is employed to study the blast seismic effect. Based on the response spectrum theory of system with single degree of freedom，the response spectrum is calculated by using analytical expression of trigonometric interpolation with great efficiency and high precision instead of piecewise linear interpolation. Response spectrum analysis of blast vibration signals in single and multi-deck blasting is performed with a vast amount of monitoring data from engineering blast. The results show that response characteristics of vibration induced by single deck and multi-deck blasting have marked differences. Multi-deck blasting not only has the good effects of reducing vibration by wave interference，but also increases the probability of selective magnification in the structural response on blasting-induced vibration. The effect of selective magnification varies with the types of structure. It is shown that the method provides an effective tool for studying blast seismic effect，especially constituting velocity-frequency safety criteria.

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CALCULATION METHOD OF ANTI-PULLING CAPACITY OF ANCHOR CABLES WITH SECONDARY SPLITTING GROUTING

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2005, 24 (14): -2414 doi:
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The secondary splitting grouting can greatly increase the anti-pulling capacity of anchor cables in the soft ground stratum. The mechanism of the increasing of the anchorage capacity is discussed in detail. The theoretical formulas of the anchorage capacity and a simplified calculation method are provided. The results are significant to the design and construction of anchor cables with secondary splitting grouting.

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MECHANISM OF EFFECTS OF TEMPERATURE AND EFFECTIVE STRESS ON PERMEABILITY OF SANDSTONE

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2005, 24 (14): -2420 doi:
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In order to study the mechanism of the effect of temperature and effective stress on permeability，the porosity and permeability tests for sandstone were conducted at various temperature and effective stress levels. The test results show that both the porosity and permeability of sandstone samples decrease with the increasing effective stress at a fixed temperature level，but the decreasing extent of porosity is much smaller than that of permeability. At a fixed effective stress level，when temperature increases from 20℃ to 60℃，the decreasing extent of the permeability of sandstone samples is about 55.81%–73.85%，but the variation range of porosity is less than 3%. According to the analysis of test results，the mechanism of the effect of temperature and effective stress on the permeability of sandstone is proposed. As far as the sandstone concerned，the effect of effective stress on permeability lies in pressure effect of effective stress on pore，especially on throat，and that of temperature lies in aggravating disaggregation of clay mineral with rising temperature and pressure effect of skeleton expansion on throat. The disaggregation of clay mineral is probably the most important factor.

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NUMERICAL ANALYSIS OF PERFORMANCE OF GEOGRIDS-REINFORCED RETAINING WALLS BY NONLINEAR FEM

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2005, 24 (14): -2428 doi:
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A numerical nonlinear analysis procedure based on finite element method is developed for the geogrids-reinforced retaining walls. The effects of both backfills and geogrids can be considered in the procedure. A case study for a large-scale test wall reinforced by geogrids，which is well documented by Royal Military College of Canada，is used to verify the reliability of the proposed numerical method. Then a comparative study is conducted for a varied range of parameters involved in the analysis such as deformation and strength properties of backfills and rigidity，length and vertical spacing of geogrids. The influence of these parameters on distribution and variation modes of stresses and deformations of the system are examined based on the computed results. It is shown that the rigidity of geogrids had a considerable effect on the behavior of geogrids-reinforced retaining walls when the backfills are of lower strength and stiffness；and that the geogrids have a limited length when the height of wall is fixed；and that the spacing of geogrids also has an effect on the deformation of the wall face. The performance behavior of geogrids-reinforced retaining wall is further discussed.

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PARALLEL 3D FINITE ELEMENT ANALYSIS AND ITS APPLICATION TO HYDRAULIC ENGINEERING

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2005, 24 (14): -2434 doi:
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The large-scale numerical analysis in hydraulic engineering gives rise to the need for high-performance computation. To meet it，the algorithm of parallel finite element based on EBE (element-by-element) method is put forward by using J-PCG (Jacobi preconditioned conjugate gradient) method. The algorithm does not invoke any special partitioning of the domain，topology of mesh or element ordering. Global stiffness matrix does not need to be formed and the decomposition of 3D complicate domain can be avoided with this algorithm. A PFEM (parallel finite element method) program is developed and implemented on cluster of workstation (COW). Then it is applied to finite element analysis of arch dam system of the Ertan Project and caverns of the Shuibuya Project. The calculated numerical results show that parallel finite element based on EBE method is applicable for large-scale numerical analysis of 3D structures in hydraulic engineering.

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ROCK STRENGTH DETERIORATION UNDER ACIDIFIED CONDITIONS AND ITS STATIC ACCELERATED SIMULATION

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2005, 24 (14): -2439 doi:
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Aimed to understand how rocks get deteriorated under acidified conditions，accelerated simulations of water-rock interaction for marble and diabase have been carried out continuously in static water surroundings with different acids (H2SO4，HNO3 and HCl) of different contents (1.0%，5.0% and 10.0%) for 900 days. The sensitivity of the deterioration of unconfined compressive strength(UCS)，tensile strength and Shore hardness to acid types and acidity，and deterioration mechanism are analyzed. The results seem to indicate that strength deterioration，surface hardness deterioration and eroded rate will nonlinearly increase with the concentration of H+ and acid treatment time；and environmental effect of the simulation conditions is directly correlated to the lithology，acid types and the concentration of H+ as well as further dissolution of the new salts in water. The sensitivity to both strength deterioration and hardness deterioration of marble and diabase under individual acid conditions is different from that under mixed acid surroundings. In the case with individual acid，vitriol and nitric acids are relatively sensitive to marble and diabase when the content of acid is less than 5.0%. However，the sensitivity will decrease and the effect on deterioration will become stable when their content is more than 5.0%. It shows that different acid types play different roles in deterioration of carbonate and silicate rocks. In the case of mixed acids，the deteriorations of strength and hardness of marble gradually increase with the increase of the content of vitriol acid. However，the activities of vitriol，nitric acid and hydrochloric acid are equal for diabase. It shows that the mechanisms of erosive function in carbonate rock are different from that in silicate rock under the mixed acid conditions. Generally，the deteriorations of strength and hardness in both marble and diabase are more intensive in the case of mixed acids than that in the individual case. Further，in both cases，the deteriorations of marble are more intensive than those of diabase，and the damage in tensile strength，UCS，and Shore hardness will decrease in order.

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INTERACTION OF SURROUNDING ROCK OR SOIL AND LINING OF A PRESSURE TUNNEL

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2005, 24 (14): -2449 doi:
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Based on Biot′s theory，the interaction of surrounding rock or soil and structure in a pressure tunnel subjected to internal water pressure is investigated by using the coupled seepage-mechanical model of porous elastic medium. Considering the relative permeability of lining and surrounding rock or soil，the tunnel is assumed to be partially sealed. So，a stress coefficient depending on the porosity of medium is proposed to determine the value of internal water pressure in medium and in pore water，respectively. The analytical solutions of stress，displacement and pore pressure are derived in Laplace transform domain with and without considering the rigidity of lining. Numerical results in time domain are obtained by Durbin′s inverse Laplace transform and used to analyze the influence of stress coefficient and relative rigidity of lining and soil on stress，displacement and pore pressure.

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TRANSMISSION MODEL OF WEAK INTERCALATION AND ITS VIBRATION ISOLATION PROPERTIES

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2005, 24 (14): -2456 doi:
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The weak intercalations have an impedance action on seismic wave propagation in spite of its adverse influence on engineering body. In the past，the adverse influence has been researched more than their properties of the base isolation. However，the research on the base isolation properties of weak intercalations can not only offer us more theoretic foundation for reducing damage and preventing disasters induced by the action of earthquake waves，but also help to explore the dynamic character of rock joints. In fact，the weak intercalations may be approximately regarded as a kind of joints when they become very thin. Based on some theories of plane elastic wave propagation，the transmission model of weak intercalations for P wave fields is established and used to analyze propagation properties varying with incidence angles，depth，impedance ratio of the weak intercalations. Finally，the mechanism of waveform distortion of transmission wave is also discussed.

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STRESS CONTROL IN HOLLOW CYLINDRICAL TORSIONAL SPECIMEN FOR STUDY OF DOUBLE SHEAR UNIFIED STRENGTH

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2005, 24 (14): -2463 doi:
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The ultimate line of the double shear strength theory in p plane is a polygonal line according to the double shear unified strength theory. The theory is simple in form and convenient to use. In order to verify the shape of the strength line of materials，the apparatus with complex stress control function is needed to reveal the strength characteristics in complex stress conditions. In the light of double shear unified strength theory，the equations for controlling stress of the hollow cylindrical specimen subject to the specific double shear stress paths are derived. The design of the specific stress paths and the stress control equation are proposed correspondingly.

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PREDICTING SLOPE STABILITY BASED ON n -SVR ALGORITHM

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2005, 24 (14): -2468 doi:
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A slope stability predicting model based on n -SVR algorithm，which uses only characteristic parameters of slopes，is put forward. To overcome the difficulty in model selection in the algorithm，leave-one-out method is used to design predicting model；and grid-search method is used to search suitable values of parameters of the predicting model. Leave-one-out method can select appropriate model objectively，avoiding the shortcoming of designing model by experience. The search result shows that with these two methods，the appropriate predicting model can be searched. Applying the predicting model to predict safety factors of 11 slopes after learning with other 71 samples；the result is satisfactory. It is more accurate than a modified BP algorithm and classical SVR；and it shows that the proposed model is effective. Moreover，a new method based on n -SVR algorithm is presented to guide slope design. It can acquire slope safety factors of different schemes by characteristic parameters of slopes quickly and accurately，and evaluate the stability of slope，which will facilitate the determining of an economic and safe slope design scheme.

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MODEL TEST STUDY ON LANDSLIDE UNDER RAINFALL AND RESERVOIR WATER FLUCTUATION

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2005, 24 (14): -2476 doi:
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The landslide model test results under the conditions of rainfall and reservoir water fluctuation from the
′2000 scientific specified plan of Monitoring and prediction of Geological Hazards of Three Gorges Region are introduced. The test systems，including indoor artificial rainfall control system，reservoir water level control system，control system of the large-scale rising and falling of experimental platform，and the measurement systems for multi-physical parameter measurement，non-contact optical displacement measurement，and g -ray water content measurement system，were set up. Taking the Shiliushubao Landslide as an example，the deformation characters of reservoir-triggered landslide are studied.

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ANALYSIS OF RHEOLOGICAL CHARACTERISTICS AND STABILITY OF SURROUNDING ROCK MASSES OF XIAOLANGDI HYDROJUNCTION UNDERGROUND CAVERNS BY USING FLAC3D

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2005, 24 (14): -2484 doi:
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The underground workshop of Xiaolangdi Hydrojunction is a large-scale underground opening complex consisting of the diversion tunnel，the main power house，the bus bar chamber，the main transformer chamber，the tailgate chamber，the draft tube and the tailrace tunnel. The three-dimensional continua fast Lagrangian analysis software FLAC3D is employed in the analysis. The viscoplastic model in FLAC3D for the rheological constitutive relation of surrounding rock masses is adopted. The three-dimensional meshes for numerical calculation have a range of 357.10 m×246.44 m×451.50 m，and have 44 600 elements and 48 705 nodes. The draft tube and tailrace tunnel’s concrete lining is simulated using the shell elements. The supporting structures of the main power house，such as prestressed cables，tension bolts and shotcrete lining，are simulated through improving rock mechanical parameters within the anchored scope. The whole excavation process is divided into seven excavation-supporting steps in the light of the practical excavation process. The time to exert excavation load for each step is set at the middle point of the corresponding step. For the application of the initial geostress，deadweight stress is selected as vertical component；and a lateral pressure coefficient of 1.0 is chosen for horizontal stress based on measured and theoretical analysis results. Mechanical parameters of rock masses are determined through back analysis of displacement measurement data of 5 years (1997－2002). Several analysis results and conclusions are given：(1) After the excavation，the horizontal displacements at the middle of the main powerhouse upstream and downstream sidewalls are considerably large with a maximum value of 1.66 cm. Only a small scope of plastic zones appears during the excavation. (2) Both the calculated and measured convergence rates are about 0.003 mm/day in the 4 years after completion of the project (1998－2002). (3) Rock creep will exist in a very long time，but the creep rate is very small and gradually reduces to an extremely small value，and no new plastic yielding occurs within 100 years considered in the calculation. So the surrounding rock masses are in good stability condition. But the creep displacement may reach to a considerably great extent and be harmful to the rock supporting structures and other concrete structures in the underground workshop.

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SEISMIC WAVE PROPAGATION IN VISCOELASTIC AND NEARLY SATURATED ROCK

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2005, 24 (14): -2490 doi:
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Considering engineering practice，seismic wave propagation in nearly saturated rock is studied by using the viscoelastic two-phase model. This model can consider the effect of the viscosity of rock skeleton and saturation degree on the propagation of the seismic wave. The propagation characteristics of seismic wave in nearly saturated rock can be understood comprehensively and the model is more reasonable than other models for study of seismic wave propagation. The effect of saturation degree，frequency，water content on the wave velocity and attenuation coefficient are studied by numerical examples；and some valuable conclusions are given.

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INVESTIGATIONS ON EVALUATING CRITERIA OF STABILITIES FOR ENERGY (PETROLEUM AND NATURAL GAS) STORAGE CAVERNS IN ROCK SALT

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2005, 24 (14): -2497 doi:
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Because of special mechanical behaviors of rock salt，evaluating criteria of stabilities have fundamental differences between energy (petroleum and gas) storage caverns in salt and in rock formations；and there are no unified criteria and design regulations for storage cavern in rock salt worldwide. The stabilities of caverns are evaluated by means of numerical analysis methods such as FEM or FLAC. Generally，most evaluations of stabilities for caverns in rock salt are carried out as follows：Firstly some criteria of caverns are set up on basis of the caverns and mechanical behaviors of rocks associated with rock salt and caprocks；Then experiments for rock salt and other rocks such as rockcap are performed，and some parameters concerned with calculation are gained；Finally analysis and evaluation for the stabilities of storage caverns could be conducted by means of the results of numerical calculation and simulation. The contents and evaluating criteria of stabilities for storage caverns in rock salt are proposed；and some formulas associated with evaluation of stabilities are given. These criteria can be divided into three aspects：(1) criteria of stabilities such as no walls spalling，no creep rupture，safe pillar control，and subsidence control on the ground；(2) criteria of tightness such as maximal interior pressure control principle；(3) and criteria of usage such as convergence rate control for caverns. Control values of stability evaluation are given according to engineering experiences for operation of some storage caverns，the utilizing ratio of strength around the cavern is no more than 40%－50% as control value of no wall spalling，and the variation of strain around the cavern is no more than 3% in Germany as control value of no creep rupture，for instances. Meanwhile，a sample in China is given. In the sample it states how to evaluate stabilities for the caverns，but it is emphasized that some aspects of the criteria are maybe modified on basis of different properties for storage caverns and rock salt.

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EARTHQUAKE RESPONSE OF SHALLOW SUBWAY TUNNELS IN SOFT FOUNDATION

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2005, 24 (14): -2506 doi:
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By considering the characteristics of soft soils in Nanjing city，a representative soft foundation is selected to be investigated. Firstly，the curves of dynamic shear modulus ratio G/Gmax and damping ratio versus dynamic strain g of the soils in this site are obtained by GZZ–1 free vibration column test system improved by Nanjing University of Technology. Secondly，as far as the Nanjing Subways are concerned，the earthquake response of shallow subway tunnels in soft foundation is analyzed by 2D finite element method. In the calculation model，the effect of soil-tunnel dynamic interaction and the nonlinear behavior of soil are considered by the equivalent linear method. It is shown that the force induced by middle and strong ground motions are very large. The damages are very likely to occur at places with central angles of ±35° or so to the top and bottom of the tunnels. These conclusions are in good agreement with records of seismic damage of subway.

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STABILITY ANALYSIS OF RANDOM BLOCK ROCK OF UNDERGROUND POWER HOUSES OF XILONGCHI PUMPED STORAGE PLANT

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2005, 24 (14): -2513 doi:
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Stability analysis of random block rock of underground power houses of Xilongchi Pumped Storage Plant is carried out by three-dimensional fissure network simulation technique and block theory；and effectiveness of anchoring support on instable block rock is checked. The rationality of reinforcement scheme and anchoring support parameters are proved. The results provide a reliable basis for project design and construction.

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RESEARCH ON COUPLING CHARACTERISTICS OF FLUID FLOW AND STRESS WITHIN ROCK

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2005, 24 (14): -2518 doi:
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Based on the review of the current research achievements in the field of coupled fluid flow and stress in rock，the research methods can be boiled down into 3 types. The first is drawing empirical formulas from coupled fluid flow and stress experiments directly. The second is establishing function according to existent empirical formulas，deducing the variable expression in the established functions by mechanical method and then determining the formulas. The third is establishing coupled relational expression by mechanical tool based on various physical models that simulate seepage phenomena. Based on this classification，the current research works are introduced with their rationality and applicability analyzed. Moreover，future development and the possible improvement are briefly discussed. Firstly，in order to fulfill the requirement of engineering application，the research of coupled fluid flow and stress in combination of porous rock and fractured rock and the corresponding numerical model should be developed. Secondly，there is great research space in the field of anisotropic coupled fluid flow and stress in rock and this work is necessary. New coupled triaxial fluid flow and stress experiment equipment should be developed to study the seepage property under true triaxial stress. Thirdly，because of non-reversible characteristics of rock deformation influence rock permeability，it is necessary to enhance the testing study on rock permeability under stress that changes in a non-monotone way. Fourthly，the research of coupled between fluid flow and stress and research of rock failure should be combined. It is very helpful to explore the inherent seepage mechanism that promotes the combination of macro-research and micro-research. Finally，it is important to take physical，mechanical and chemical effects into account in the coupled research because the three effects appear at the same time when water flows in rock.

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3D VISUALIZATION MODEL OF MINING GEOTECHNIQUE AND ITS APPLICATION

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2005, 24 (14): -2526 doi:
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It is an important development direction for mining geotechnical engineering to build perfect 3D visualization model of mining geotechnique，which provides model information for analysis and estimation of stability timely and exactly，and integrative information to help geotechnical engineers to make right judgments. This paper integrates the characteristics of mining geotechnique information，utilizes the module techniques of computer，realizes the visualization of mining geotechnical engineering computation figures and applies it successfully to mining engineering practice.

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RESEARCH ON CHARACTERISTICS OF WAVE PROPAGATION IN PILE ENCLOSED BY SOILS

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2005, 24 (14): -2531 doi:
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The variation of velocity and the absorption coefficient of waves in piles enclosed by soils with different Young modulus and damping coefficients are studied systematically by means of numerical analysis. It is shown that the wave velocity decreases with the decreasing of Young modulus and increasing damping coefficients；and the absorption coefficient increases with the increasing of Young modulus and damping coefficients. The absorption coefficient and wave velocity are approximately of negative linear correlation. The result of numerical calculation and measured data show that，when the excitation pulse width becomes bigger，the propagation velocity increases and the damping coefficients decrease. As the transmitting characteristics are different for pulses with different frequency components；the soils around the pile has the frequency dispersion and dissipation effect on the waves. The measured curve can be decomposed into different waveband components by wavelet analysis. The characteristics of dispersion and dissipation of soils to waves can be investigated by comparing the excited signal and the reflection curve.

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NUMERICAL ANALYSIS OF THE VENTILATED EMBANKMENT WITH THERMAL INSULATION LAYER IN QINGHAI—TIBET RAILWAY

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2005, 24 (14): -2537 doi:
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In order to prevent embankment from absorbing heat in hot season，the ventilated embankment with thermal insulation layer is proposed. The thickness of heat insulator is 20 mm and paved 20 cm above upper surface of ducts. The finite element formulae are derived from the differential equation of three-dimensional temperature fields involving phase change by Galekin method. The temperature distributions of the ventilated embankment with and without thermal insulation layer are calculated respectively under the case that the annual mean air temperature in Qinghai-Tibet Plateau will be warmed up by 2.6℃ in the future 50 years and the mean annual temperature at the native surface is about －1℃. The results indicated that the insulation layer reduces little absorption of heat for permafrost under embankment in the case and the effect of heat insulation is not so good. The conclusions are given in term of the results of analysis and comparison.

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RESEARCH ON THICKNESS OF REFORMATIVE SOIL IN ROADBED

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2005, 24 (14): -2546 doi:
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The essential of decreasing temperature by reformative soil in cold regions is the change of the transfer mechanism of reformative soil layer through changing the structure of soil. According to mechanism of heat transfer in porous media，the minimum reformative soil thickness that is needed to form heat convection in the soil layer is induced by analysis of natural convection heat transfer in reformative soil. The results can provide references to the application of reformative soil to engineering projects in cold regions.

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RESEARCH ON BEARING CAPACITY AND SETTLEMENT PROPERTY OF PRESSED-IN PILE IN XI′AN LOESS AREA

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2005, 24 (14): -2548 doi:
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By analyzing the load transmission mechanism of pressed-in pile in loess foundation，a kind of hyperbolic curve is proposed to fit the load transmission function between pile and its neighboring soil. Two parameters Kc and Ke are introduced to modify the c and E0 of soil by considering the influence of compacting effects caused by pressing-in of piles in loess. Based on test data of the 96 piles in Xi′an area with detailed soil and pile parameters and p-s curves，an experiential formula of Kc and the CPT resistance qc of the soil around pile base and the empirical relationship between Ke and concrete grade are established. The proposed method is validated through the comparison between the results of calculated and tested p-s curves.

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STRENGTH CHARACTERISTICS AND MECHANISM OF LOESS SOLIDIFIED WITH NEW POLYMER MATERIAL SH

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2005, 24 (14): -2554 doi:
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Polymer materials have wide prospect of application to soil solidification engineering. SH is a new water-soluble solidification material. Based on the uniaxial compressive strength test，and modern analysis methods such as X-ray diffraction(XRD)，Fourier transform infra-red(FTIR)，scanning electron microscope，X-ray energy dispersive spectrum(EDS) and surface area/micro porosity，the mechanism and strength characteristics of the SH solidified loess are analyzed. The research results show that the strength of the solidified loess increases with the content of SH，but the interrelationship is not linear，and long-term strength of solidified loess is very high. After loess is solidified by SH，the compressibility decreases，and the collapsibility is lost. The admixing of the SH changes the structure of the loess. It makes the connection of loess grains stronger. By hydrogen bond，ion exchange，absorption of macromolecular and flocculation；the physicochemical interaction may occur between SH and the loess. This may be the main reason for the improvement of the strength of the loess.

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TWO-NODE CONTACT ELEMENT METHOD AND ITS NUMERICAL VALIDATION

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2005, 24 (14): -2560 doi:
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A new type of contact element，two-node contact element (TCE)，is proposed. The TCE is composed of two nodes and its impacting domain. Because it doesn′t use the interpolation method as the traditional joint element does，but employs the impacting function as its interpolation function；it shows considerable flexibility in dealing with the more complex joint cases. It means that the mechanical behavior of one small joint section，which possesses one contacted node-couple，is only determined by the behavior of its own contacted node-couple，and is not related to the behavior of node-couples of other joint sections. The special constitution of TCE makes its application more extensive. TCE stiffness matrix is deduced. At last，the proposed method is employed to model a simple jointed rock mass，then the numerical results from TCE is compared with that from traditional 4-node joint element. The comparison shows that a well agreement exists between the two methods，which indicates that the proposed method is valid and applicable.

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PRINCIPLES OF PIPE ROOF APPLIED TO SHALLOW-BURIED TUNNELS IN SOFT GROUND

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2005, 24 (14): -2565 doi:
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Aiming at the argument that whether the large pipe roof or small pipe roof should be adopted in the construction of shallow-buried tunnels in soft ground，the function mechanism of pipe roof is analyzed and the requirements for‘shed’and‘frame’to developed on the tunnel arch are put forward based on the in-situ measurement in Jiefang Road Tunnel in Hangzhou City and centrifuge model tests. According to the theory of shed and frame，it is pointed out that pipe roof can consolidate the ground and disperse the ground stress and reduce the excavation release stress. It was demonstrated that，in the pipe roof and grating system，the pipe roof can disperse the ground stress and the grating is load-bearing body based on the 3D FEM analysis of one underground passage located in Shanghai. The design and construction parameters for the three kinds of the pipe roof systems are also put forward. The pipe roof system can be divided into three kinds according to the pipe diameter，namely small pipe roof，medium pipe roof and large pipe roof.

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APPLICATION OF PHP SLURRY TO DRILLING OF OVERLENGTH AND EXTRA-LARGE-DIAMETER BORED PILES

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2005, 24 (14): -2571 doi:
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PHP (partially hydrolyzed polyacrylamide) slurry is especially suitable for the drilling of overlength and extra-large-diameter bored piles. Its economical efficiency and construction efficiency are dependent on the following key factors：manufacturing of raw materials，manufacturing process，cycling system and construction control. According to geological and hydrologic conditions of the site of Su-Tong Bridge，the testing pile project has adopted PHP slurry cycling system，which has been proved in the practice to have achieved thickness of mud cake around piles less than 1 mm and thickness of sediments at pile tip of zero.

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GREY-CORRELATION ANALYSIS OF FACTORS INFLUENCING DEFLECTION OF THE ROUND FOUNDATION PIT OF THE SOUTH ANCHORAGE OF WUHAN YANGLUO YANGTZE RIVER HIGHWAY BRIDGE

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2005, 24 (14): -2576 doi:
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To ensure the security of the Yangtze River levee nearby，the deflection of the diaphragm wall of the round foundation pit for the south anchorage of Wuhan Yangluo Yangtze River Highway Bridge must be strictly controlled. So after the brief presentation of the construction process of the project，factors that contribute to deflection of the diaphragm wall are examined；and three parameters，namely depth of excavation layers，thickness of inner lining and width of excavation part，are recognized as the main factors. Then grey-correlation theory is applied to analyze the correlation between these parameters and deflection of the diaphragm wall. It is shown that depth of excavation layers and width of excavation part have more influence than thickness of inner lining. Therefore，to restrict the deflection of the diaphragm wall，it is more efficient and economical to adjust the depth of excavation layers and/or the width of excavation part than to increase the thickness of inner lining. The analysis method and the conclusion can be applied to this project and other similar projects.

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EXPERIMENTAL STUDY ON DAMAGE CHARACTERISTICS OF CONCRETE BY USING WAVELET THEORY

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2005, 24 (14): -2581 doi:
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A series of standard cube concrete of different grades were tested under impact load to study the damage characteristics of concrete. The experiments indicate that concrete of different grades under impact load has different ranges of damage；its interior damage is anisotropic；and its resistance to impact increases with the increasing of its strength. The interpretation of arrival time of head waves is accurate and reasonable by using ultrasonic velocity to describe material interior damage and wavelet transform noise cancellation method to treat ultrasonic signals. Regularities of energy distribution in each wave band have evident changes with the change of damage after the decomposition of ultrasonic signals by wavelet. It also illustrates that energy is more sensitive to damage than ultrasonic velocity is when energy distribution in one wave band is used to describe damage.

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NUMERICAL ANALYSIS OF JOINT TYPES BETWEEN TOE SLAB AND FOUNDATION OF CFRD IN ALLUVIAL DEPOSIT LAYER

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2005, 24 (14): -2588 doi:
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Two types of joints，the rigid joint and the flexible joint，between toe slab and foundation of the concrete-faced rockfill dam(CFRD) of the Nalan Hydropower Power Station are analyzed by 3D elastoplastic finite element method. Numerical results show that the joint types make small difference to stress-strain behavior of dam，dam foundation and face slab，and they have no obvious influence on stress behavior of toe slab and diaphragm wall，but obvious influence on deformation behavior of toe slab and diaphragm wall. The deformations of toe slab and diaphragm wall in the rigid joint are smaller than the flexible joint. The results of the rigid joint show that deformations of facing joint are quite big，even exceed the deformation capacity of common sealing structure. The flexible joint is recommended based on this numerical analysis.

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DESIGN METHOD FOR CROSS-SECTION SIZES OF GRIDS INSERTED IN THE FRONT OF A BOX CULVERT SURROUNDED BY PIPE-ROOF

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2005, 24 (14): -2593 doi:
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[PDF 55 KB] (1009)

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The subway crossing project through Hongxu Road in Shanghai is the pipe-roof project with the biggest cross-section box culvert up to now in the world. It is constructed in saturated soft soil stratum in the Beihong Road located in the middle ring-road in Shanghai. In order to keep cutting surface stable during pushing the box culvert in the front of which many steel grids are inserted；it is very important to design rational sizes of grids. According to analysis of soil arch effect near the cutting surface of the back end of a grid，rational design approach of cross-section sizes of grids is given on the basis of three important conditions，namely mechanical equilibrium equations，shear intensity principle of soil，and self-stability condition of soil mass. Its concrete calculation procedure is given in detail with the practical project.

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COMPLEX METHOD BASED ON MINIMUM SIMILARITY DEGREE SUBSTITUTING RULE AND ITS APPLICATION TO SLOPE STABILITY ANALYSIS

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2005, 24 (14): -2597 doi:
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[PDF 93 KB] (988)

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A modified search strategy is presented to improve the global search ability of the basic complex method. A better design point can be located on the optimization line of each design point of the current complex respectively. Several new complexes are thus obtained by replacing each design point with its better design point. The new complex with the strongest diversity is the expected one in the current iteration，thereby defining a modified complex method，which is as straightforward as the basic complex method. The ability of the new complex method to find the global optimum is verified in the search of the critical failure surface with the true minimum factor of safety of two non-homogeneous soil slopes.