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2003, 22 (06): 0-0 doi:

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CENTURY ACHIEVEMENTS AND NEW HISTORICAL MISSION OF ROCK MECHANICS AND ENGINEERING IN CHINA

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2003, 22 (06): 867-867 doi:

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This paper deals with the development issue of rock mechanics and engineering in China. The major achievements gained in the fields of rock mechanics study and engineering practice are briefly summarized. The paper shows the new opportunities faced to young generation of rock mechanics experts in connection with national development schemes. The author suggests that the rock mechanics community should pay attention to the study of some mechanisms of coupling processes in rocky mechanics and multiple meta-synthetics approaches to rock engineering problems.

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BRIEF REVIEW OF THE STRENGTH AND DEFORMATION CHARACTERISTICS OF SEDIMENTARY SOFT ROCK

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2003, 22 (06): 872-872 doi:

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The strength and deformation characteristics of sedimentary soft rock evaluated in relation to several large-scale research and construction projects in Japan are reviewed. The elastic stiffness at small strains，non-linearity due to strain and pressure level，and viscous properties are described. The elastic stiffness from triaxial tests using high-quality core samples while measuring stresses and strains accurately is basically the same as the corresponding value from field shear wave velocity. It is necessary to take into account the dependency of stiffness on shear strain and pressure level，which could be evaluated by relevant laboratory stress-strain tests while referring to results from relevant field loading tests. Loading rate effects due to the material viscous properties could be simulated by a non-linear three-component model.

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EXAMINING ANISOTROPY OF SEDIMENTARY SOFT ROCK

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2003, 22 (06): 894-894 doi:

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The inherent anisotropy of stiffness and strength of about 2 million years old sedimentary soft mudstone was investigated using core samples obtained from 50 m deep testing tunnel. In the triaxial compression test，the elastic modulus and compressive strength of the samples with the axis being horizontal in-situ were slightly larger than those with the axis being vertical，but the difference is not larger than 30%. So，strong anisotropy of the stiffness and strength was not seen in the site. The inherent anisotropy would depend on at least the geological history，and original rock type and depositional environment should be considered.

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FLUID INCLUSIONS AND THERMAL MICROCRACKING
IN INADA GRANITE

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2003, 22 (06): 899-899 doi:

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By direct microscopic observations of thin section of Inada granite in the heating process，decrepitation temperature of fluid inclusions in quartz and feldspar was determined to be in a range from 170℃ to 550℃，and thermal microcracking due to the decrepitation of the fluid inclusions was ascertained. Additionally，microstructural features of the microcracks induced by the decrepitation，such as the length，the orientation of the microcracks，were interpreted. It is likely that there is the universality with respect to the basic characteristics of the decrepitation of the fluid inclusions in all granites.

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CREEP BEHAVIOR OF SEDIMENTARY SOFT ROCK UNDER
TRIAXIAL COMPRESSION

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2003, 22 (06): 905-905 doi:

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In the laboratory of constant temperature-humidity，triaxial compression creep experiments were conducted under different stress states on three kinds of sedimentary soft rock. A lot of experiment results are examined and analyzed by five-element rheologic model and constitutive equation of variable compliance type. The relationship among many factors are obtained on the creep behaviour of sedimentary soft rock，such as axial strain，axial strain ratio，axial stress，and axial stress ratio.

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TENSILE STRENGTH OF GRANULAR MATERIALS*

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2003, 22 (06): 913-913 doi:

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The tensile strength of a single soil particle is usually measured indirectly by compressing the grain between flat platens until failure occurs，and is defined as the tensile stress at whole-particle fracture. The tensile strength appears to decrease monotonically with the diameter of particles，and is usually characterized by the Weibull statistics. For granular materials，it is impossible to measure constant tensile strength，unless the flaw effect is taken into account in the framework of fractal. The fractal dimension of flaw distribution equals to that of the fragmentation of granular materials. The Weibull statistics is modified using the fractal model of flaw distribution. Goodness-of-fit statistics shows that the modified model fits the experimental data much better than the conventional model. The modified model has only one parameter，the fractal dimension of fragmentation D，which can be determined using the mass-size distribution.

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THEORY AND APPARATUS FOR TESTING LOW-PERMEABILITY OF
ROCKS IN LABORATORY

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2003, 22 (06): 919-919 doi:

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In order to determine the low permeability of rocks both rapidly and reliably in laboratory，the rigorous analytical solutions for various kinds of laboratory permeability tests are derived. A versatile laboratory permeability testing system is also developed. This system can implement constant-head，constant flow-rate and transient-pulse permeability tests of specimen under high confining and pore pressures. Testing results demonstrate the effectiveness of both the rigorous analytical solutions and the testing apparatus.

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NUMERICAL MODELLING OF ROCK FALL USING EXTENDED DDA

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2003, 22 (06): 926-926 doi:

[PDF] 430 KB (1589)

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The reasonable design of protective structures to mitigate the hazards from rock fall depends on the knowledge of motion behaviors of falling stones，such as the falling paths，velocities，jump heights and distances. Numerical simulation is an effective way to gain such kind of knowledge. In this paper，the discontinuous deformation analysis (DDA) is applied to rock fall analysis. In order to obtain more reliable results，the following improvements and extensions are made on the original DDA. (1) Solve the problem of block expansions due to rigid body rotation error. (2) Add the function of modeling the drag resistance from air and plants so that the velocities of falling stones obtained by simulations are good enough in agreement with those by experiments in situ. (3) Add the capability to consider energy loss due to block collisions so that the jumping heights and distances obtained by simulations are good enough in agreement with those by experiments even for the slope with very soft layer on its surface. One of application examples is presented to show that the extended DDA is very effective and useful in rock fall analysis. Therefore，the presented method is expected to be put into wide use in slop stability analysis.

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HIGH ORDER RECTANGULAR ELEMENT OF MANIFOLD METHOD

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2003, 22 (06): 932-932 doi:

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The high order displacement function of rectangular element of manifold method is developed based on the theory of manifold method. This new method can simplify the forming of the mathematical meshes and physical covers，reduce the number of small physical covers，and precisely calculate the strain and stress by using the simplex integration. The linear cover displacement function is mainly discussed. The stiffness matrix is formulated. The calculation results，with an example shown，demonstrate that high order rectangular element of manifold method can get more accurate strain and stress.

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THREE DIMENSIONAL DISCONTINUOUS DEFORMATION ANALYSIS (3D DDA) AND ITS APPLICATION TO THE ROCK SLOPE TOPPLING

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2003, 22 (06): 937-937 doi:

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Numerical simulations are very important to the disaster preventions in rock slope engineering，and many researchers pay attention to the developments and applications of numerical analysis methods in this field recently，because of the developments of computer science. In order to simulate the behaviors of rock slopes with discontinuities more precisely，the numerical method is required to consider the effects of distributions of discontinuities，terrains，contacts among blocks and the large displacements in three dimensions. In this paper，both the theory of three dimensional discontinuous deformation analysis(3D DDA) and its application to simulate rock slope failure problems are discussed. DDA belongs to the discrete numerical analysis methods，and the contact judgment and contact force computation should be concerned. The contact forces are produced when blocks contact to each other. Usually，normal contact spring is employed to calculate the normal contact forces to prevent blocks from penetrating to each other during contacts，and the normal contact spring is deleted when blocks are leaving. In addition，the failure along discontinuous surfaces can be simulated easily by applying the Mohr-Coulomb failure criterion. The appropriate contact spring arrangement in 3D DDA follows the criterion of ‘no-penetration and no-tension’to obtain correct contact forces during contacts. The new approach has been successfully applied to simulate a rock slope toppling at Amatoribashi-nishi site in Japan. The simulation results are quite good in agreement with the video pictures obtained from the field. It is believed that the simulation is very helpful on investigation of the failure mechanism and process，and can provide useful knowledge to study the similar events in future.

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APPLICATION RESEARCH ON NON-SIMULTANEOUS COUPLING CALCULATION OF DEFORMATION AND SEEPAGE WITH
MANIFOLD METHOD AND FEM

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2003, 22 (06): 943-943 doi:

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The calculation code including manifold method (MM) and finite element method (FEM) is developed to study the non-simultaneous coupling problem of stress-strain and seepage for discontinuous material. A simple rock slope model is used to simulate the failure development process of the rock blocks due to the action of water pressure change along rock fracture surface. The calculated result shows that the presented coupling analysis method is effective for the coupling problems of discontinuous rocks from small deformation to failure process.

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APPLICATION OF UBIQUITOUS JOINT MODEL IN NUMERICAL MODELING OF HILLTOP MINES IN JAPAN

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2003, 22 (06): 951-951 doi:

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Numerical modeling of three cases (Fuka Mine，Okayama；Shouda Mine，Okayama；Tokiwa Mine，Fukushima) of mining in Japan using FLAC (fast Lagrangian analysis of continua) is introduced to evaluate the stability of hilltop excavation. Ubiquitous joint model is adopted to account for the presence of weak planes，such as weathering joints，bedding planes，in FLAC Mohr-Coulomb model. By studying the distribution of stress，displacement and safety factor，the stability of excavation can be evaluated and new suggestions based on the numerical modeling process can be presented. Further consideration and methodology of the numerical modeling method are also discussed.

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3D NUMERICAL SIMULATION ON THE INFORMATION-ORIENTED CONSTRUCTION FOR THE DEEP UNDERGROUND HOUSES

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2003, 22 (06): 957-957 doi:

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Modeling the effect of blasting-caused damage，anisotropy of rock masses and excavation sequence on deformational behaviour and stability of large-scale underground houses is important in the design and information-oriented construction of the pumped storage power plant. A powerful three-dimensional numerical method that can be applied for that purpose is presented in this paper. The influence of damage caused by blasting and discontinuities in rock masses on the stability of houses is considered by reducing the deformation coefficient E of the surrounding rock masses based on the relation to seismic velocity Vp. Numerical simulations of the underground excavation of the Omaru Pumping-up Hydroelectric Power Plant，which is one of the big construction projects in Kyushu island，Japan，were carried out to evaluate the influence of damage caused by blasting and reinforcement by rock bolts on the stability of powerhouses. The damaged range and mechanical properties of rock masses near to the walls of houses are determined by using the back analysis approach in which three lines of the measurement results during the arch part excavation process were used to verify the simulations. Finally，applying the improved model and properties of rocks，the house stability and reinforcement effect of the preliminarily designed support system are also estimated for the safety in the coming several bench excavation process.

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PROGRESS ON NUMERICAL MODELING OF GEOTHERMAL EXTRACTION DEVELOPMENT FOR OGACHI HOT DRY ROCKS

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2003, 22 (06): 965-965 doi:

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GEOTH3D，the coupled heat transportation and water flow source code for numerical simulation of geothermal power development experiment for the hot dry rocks in Ogachi，Akita Prefecture，is developed by Central Research Institute of Electric Power Industry of Japan，and introduced in this paper. Its theory，feature，application situation and some problems are described. With the reference to the advance of related software in the world，the coming tendency for the further efforts is discussed.

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GIS METHOD FOR SLOPE-UNIT-BASED 3D LANDSLIDE
HAZARD EVALUATION

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2003, 22 (06): 969-969 doi:

[PDF] 657 KB (1112)

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Based on a new geographic information systems (GIS) grid-based 3D deterministic model and taking the slope unit as the study object，the landslide hazard is mapped by the index of the 3D safety factor. Assuming the initial slip as the lower part of an ellipsoid，the 3D critical slip surface in the 3D slope stability analysis is obtained by means of a minimization of the 3D safety factor using the Monte-Carlo random simulation. All the calculations are implemented by a computational program 3DSLOPEGIS in which a GIS component is used for fulfilling the GIS spatial analysis function.

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STABILITY ANALYSIS OF LANDSLIDE BASED ON MECHANICS PRINCIPLE IN GIS

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2003, 22 (06): 977-977 doi:

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A new method for stability analysis of landslide，based on mechanics principle in GIS，is researched，and it will provide a new way for integrated evaluation on landslide stability. In this method，interactive conversion technology between 2D and 3D geologic information，spatial analysis technology of GIS，and Avenue of ArcView GIS are used.

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CONSTRUCTION AND APPLICATION OF GIS-BASED MODEL FOR SUBSIDENCE PREDICTION

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2003, 22 (06): 981-981 doi:

[PDF] 443 KB (742)

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GIS raster digitized model with face element is proposed and constructed. The displacement，stress and strain can be calculated with this model for any point in any overburden layer due to mining. Finally，the visual results are presented by coupling system in the case study，which are good example for the advanced application of geomechanics coupled with GIS.

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GIS-BASED STUDY ON ASSESSMENT SYSTEM FOR
ASPHALT MASTIC DETERIORATION

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2003, 22 (06): 985-985 doi:

[PDF] 393 KB (1143)

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Based on spatial data model on the GIS platform，an assessment system for asphalt mastic deterioration of water pumping storage power station is developed. The statistical information of wrinkles due to deterioration，such as length，area，etc.，can be extracted. After sophistication process of wrinkles，the fractal dimension can be calculated as a factor to assess the current deterioration condition. The system is implemented by the general technology of COM components between spatial data model and GIS，and could be a powerful tool for the other potential applications of GIS into rock mechanics for the different spatial analyses.

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CO2 AQUIFER STORAGE AND THE RELATED ROCK
MECHANICS ISSUES

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2003, 22 (06): 989-989 doi:

[PDF] 291 KB (1334)

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Carbon dioxide (CO2) is one of the major greenhouse gases whose concentration in the atmosphere has led to a significant climate change. The greenhouse issue has become a global concern，and some of major developed countries have devoted intensive effects to the development of various CO2 emission control technologies. CO2 aquifer storage is one of the technologies. The generic idea of CO2 aquifer storage is to store the gas in deep permeable sedimentary formations that are constrained by impermeable caprocks so that the gas can be almost completely isolated from the atmosphere for a very long period. Scientific evidences from nature analogues，laboratory experiments and computer simulations indicated that the geologic formations with suitable structure and hydrogeologic conditions are able to trap the gas. Cost estimations and industrial practices also showed that the existing technologies enable the storage with a cost lower than the carbon tax. Our investigations revealed that Japan has many promising storage sites，on land or off shore，with large storage capacities. A considerable part of them are close to emission sources，where there is no need for main pipeline，and therefore， the low-cost storage is possible.
The mechanical stability of a storage site is of critical importance for implementing the storage practice in Japan. However，the long-term mechanical process is involved in crustal activities，and geo-chemical and hydrogeologic processes. Such complex coupled processes are difficult to quantitatively assess. At this moment，it is recommended that the relatively stable sites for near-future storages can be found out through surveying and analyzing the information on present and historic geologic activities. However，the development of accurate quantitative assessment technologies is still important for finding more suitable sites and enhancing the contributions of aquifer storages to the emission cutting. This requires a deep understanding of such complex coupled processes，and a drastic improvement in exploration，monitoring and simulation techniques.

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FAULTING-INDUCED PERMEABILITY CHANGE IN SHIRAHAMA SANDSTONE AND IMPLICATION FOR CO2 AQUIFER STORAGE

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2003, 22 (06): 995-995 doi:

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The long-term safety assessment of CO2 aquifer storage requires a deep understanding of permeability evolution during inelastic deformations in sedimentary rocks. The permeability change has been measured in the entire process from elastic，plastic，post-failure to axial stress unloading for Shirahama sandstone subjected to triaxial compressions under various confining pressures. The measurements revealed that the confining pressure plays an important role in controlling inelastic deformation behavior and the tendency of the permeability evolution. In the brittle faulting regime under a low confining pressure，significant increase in permeability accompanied by dilatancy can be observed. In brittle-ductile transition regime and ductile regime，faulting or inelastic deformation does not necessarily and significantly enhance the permeability，and the permeability during deformation is lower than their corresponding initial values. Microscopic observations revealed that the two mechanisms：(1) shear-enhanced cracking，and (2) grain crushing，are responsible for these inelastic deformation and permeability evolution tendency. The presented results suggested that storing CO2 in those sites where ductile deformation prevails may be more safe.

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SEISMIC WAVE VELOCITY MONITORING OF CO2 MIGRATION IN POROUS SANDSTONES SATURATED WITH WATER

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2003, 22 (06): 1002-1002 doi:

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Laboratory experiments were conducted to measure the compressional wave velocities under hydrostatic pressure in Shirahama and Tako sandstones with a porosity of 12% and 24%，respectively. In dry samples，the pressure dependence of velocity is ascribed to the difference in pore structures. Velocities were also measured to map the movement of the injected CO2 within water-saturated samples during CO2 injection. In the water-saturated samples， velocity changes caused by the CO2 injection are typically on the order of 10%. A series of seismic tomography experiments are conducted on porous sandstone samples to demonstrate the use of cross-well seismic profiling for monitoring the migration of CO2 in geological sequestration projects.

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THREE-DIMENSIONAL ANALYSES ON THE LATERAL BEARING CAPACITY OF RIGID PILE FOUNDATION ON ROCK SLOPE

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2003, 22 (06): 1008-1008 doi:

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To develop the rational numerical method for predicting the deformation and failure of the rigid pile foundation on rock slope，a series of nonlinear elasto-plastic FEM analyses were conducted to simulate the field experiment on the bearing capacity and failure deformation of rigid pile foundation on rock slope under the lateral loading. In the analyses，rock was supposed to be a elasto-perfectly Mohr-Coulomb plastic material with or without considering the low-tension strength effect. The results obtained from the FEM analyses were compared with that of the field experiment. It was found that the load-displacement relation and the failure mechanism of the rigid pile foundation obtained from the 3D-FEM analyses，in which the low-tension strength effect for rock was considered，has a good agreement with the field experimental result. In addition，by making use of the above rational numerical method，the effects of distance from pile foundation to the top of slope and slope angle on the lateral bearing capacity were also successfully evaluated.

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THREE-DIMENSIONAL SLOPE STABILITY ANALYSIS BASED ON NONLINEAR FAILURE ENVELOPE

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2003, 22 (06): 1017-1017 doi:

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The effects of nonlinearity of strength envelopes on 3D slope stability analysis are investigated. A power relation for the nonlinear envelope is employed to derive the 3D factor of safety equations of an extended Spencer method which satisfies both force equilibrium and moment equilibrium. Then，a search procedure is presented based on dynamic programming to determine the 3D critical slip surface for a general slope. Linear and nonlinear strength envelopes used for slope stability computations are obtained by fitting curves to the 103 strength data of consolidated-undrained (CU) triaxial compression tests for compacted Israeli clay. Results of a typical 3D problem show that a linear approximation of the nonlinear strength envelope may lead to a significant overestimation of calculated safety factors.

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COUPLING MODEL OF BOLT REINFORCEMENT SYSTEM AND APPLICATION

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2003, 22 (06): 1024-1024 doi:

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A normal analytical model for reinforcement is proposed，on the basis of refined Shear-Lag model，to describe the mechanical coupling at the interface between reinforcement and rock/soil mass. Coupling and decoupling behavior of reinforcement in pullout test is analyzed，and a new method is suggested to evaluate actual shear strength of interface between reinforcement and rock/soil mass. Average shear force is smaller than actual shear strength. The difference is related not only to the embed length of reinforcement，but also to the deformation modulus of matrix material. Interaction influence of anchor length and matrix¢s deformation modulus is often ignored in normal pullout test，which may leads to large deviation. Rational anchor length is suggested for pullout test. Analysis of bolt around tunnel shows that there is a pullout area，neutral point and anchor area along bolt. The position of neutral point is not only determined by geometry of tunnel，but also influenced by the rock mass properties. Theoretical prediction coincides well with testing data.

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ARRAY MICROTREMOR SURVEY AND ITS APPLICATION TO CIVIL ENGINEERING

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2003, 22 (06): 1029-1029 doi:

[PDF] 519 KB (1782)

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The Array Microtremor Survey(AMS) is briefly presented and its application is discussed to geotechnical investigation for civil engineering based on field experiment data. For this method，first，microtremors are observed simultaneously by a number of seismometers deployed in an area on the ground surface，then，phase velocity of surface wave is calculated from the observed microtremors using stationary stochastic process theory，finally，the subsurface shear wave velocity structure is estimated by phase velocity inversion. To study the application of this method to shallow geotechnical investigation for civil engineering，a series of field experiments and theoretical analyses are made. The result of the study shows that shear wave velocity structure given by AMS agrees well with the result of the conventional P-S log method in general. Though the AMS is slightly inferior to the PS log in resolution，it gives good accuracy for thick layers. Unlike the P-S log method，the AMS does not need to drill a borehole，thus it can save both money and time and be gentle to the environment. Furthermore，since the traffic vibration is no more a noise，but it provides a source for high frequency signal，the AMS method can be considered as an inexpensive，fast and gentle method for geotechnical investigation in urban area.

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STUDY ON THE DETRITUS FROM DIFFERENT EXCAVATION
MACHINES AND METHODS

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2003, 22 (06): 1037-1037 doi:

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The particle size distribution of detritus sampled from different excavation machines and methods is calculated and analyzed. The comparison of the results shows that the particle size distribution of detritus follows the same mathematical model and is of similar trends.