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2007, 26 (3): 432-432 doi:

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2007-03期目录

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LARGE-SCALE LANDSLIDES AND THEIR SLIDING MECHANISMS IN CHINA SINCE THE 20TH CENTURY

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2007, 26 (3): 433-433 doi:

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The landslides occur frequently in China. In particular，large-scale landslides are dominant and extremely important. In West China，the large-scale landslides are notable for their scale，complex formation mechanism and serious destruction，which are typical and representative in the world. Data were collected from some typical large-scale landslides occurred in mainland of China since the 20th century. Among these cases，nine landslides were comprehensively analyzed and discussed. These cases represent different geological conditions，different triggering mechanisms and induced factors. This study shows that the fundamental cause for large-scale landslide in China is due to the topographical and geomorphological conditions. About 80 percent of large-scale landslides were found in the first slope-descending zone of the mainland topography around the eastern margin of Tibet plateau. Moreover，this area is the most active area of the plate tectonic activities. The intensive interactions between the endogenic and epigenetic geological process cause serious dynamic change of the high steep slope，which are resulted in the development of large-scale landslides. Strong earthquake，extreme weather conditions and the global climatic change are the main triggering factors of large-scale landslides. In South China，it is easy to trigger large-scale landslides when storm causes 200–300 mm/d of heavy rainfall. In Northwest China，the thawing of the frozen layer in spring is the main cause of large-scale landslides in loess region. In recent years，global warming causes the temperature to rise，snow line to shift，glacier recession and glacier lakes to collapse. These factors are also the triggering factors of large-scale landslides in some areas. In addition，the causation of more than 70 percent of large-scale landslides is closely related to the human activities. Detailed analyses of the cases show that the mechanisms of large-scale landslides in China are complex. The large-scale landslides can be summarized into three types：rock landslides，soil landslides and landslides in debris. The typical geomechanical models of large-scale landslides in rocks are shown as following：the “three sections” model(i.e. sliding-tension cracking-shearing)，“retaining wall collapse”model，“horizontal-pushing”model in horizontal strata，large-scale toppling model in anti-dip strata，and the creep-bending-shearing model，etc.. Each model corresponds to some specific rock structure conditions and deformation processes. When large-scale rock landslides occur，they are generally accompanied by the suddenly brittle failure of the“locked section”along the potential sliding surface. The“locked section”is extremely important to the deformation control and stability of the rock slope，which is also the key factor for the assessment of slope geohazard and for the development of control methods. It is shown in engineering practice that the correct understanding and using of geological and mechanical model are the fundamental keys for the prevention of large-scale landslides.

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THEORETICAL VERIFICATION OF RIGOROUS NATURE OF SIMPLIFIED BISHOP METHOD

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2007, 26 (3): 455-455 doi:

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Although the inter-slice shear forces are ignored in the simplified Bishop method and the complete equilibrium conditions are not completely satisfied，the achieved factors of safety of circular slip surfaces are in excellent agreement with the results of those rigorous methods. This is the one of the most difficult problems that have not been solved for a long time. The study shows that the absence of inter-slice shear forces in the factor of safety equation of the simplified Bishop method does not mean they actually disappear，but a certain term involving inter-slice shear forces equals zero. A set of inter-slice shear forces could be always found where not only the sliding body satisfies the complete equilibrium conditions，but also makes that term equals zero. Therefore，it is implied that the simplified Bishop method automatically satisfies the rigorous equilibrium conditions，which can be regarded as a rigorous inter-slice method.

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STUDY ON INTERACTION BETWEEN BACK POWERHOUSE SLOPE AND ARCH DAM OF GEHEYAN HYDROPOWER STATION

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2007, 26 (3): 459-459 doi:

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The interaction between the slope and dam body is evaluated by establishing numerical models of the slope and the dam simultaneously and adopting iterative algorithm based on the purpose of slope stability analysis and the dam body stress verification. This method not only improves the efficiency of modeling，but also reduces the difficulty of model construction. In order to simulate the construction processes and reveal the stress and deformation processes of the dam body and slope，the application of arch dam thrust is employed based on the states of excavation，unloading and reinforcement that have already been completed；and the effect of water pressure of the reservoir is also considered. The result indicates that the interaction between the slope and dam body is not remarkable；and the effect of the dam thrust against the slope displacement is within 30 m around the dam abutment，which means that the whole stability of the slope and the dam body will not be greatly influenced. The achieved result proves the rationality of the dam design；and it can provide references to the slope management and dam operation.

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NONLINEAR CREEP DAMAGE CONSTITUTIVE MODEL OF ROCK SALT AND ITS APPLICATION TO ENGINEERING

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2007, 26 (3): 467-467 doi:

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Rock salt is considered as a potential medium for energy storage，nuclear waste deposit for its excellent creep，low permeability and damage recovery behaviors. Based on laboratory creep test results of rock salt，nonlinear creep constitutive model and damage evolution equation are suggested. The developed constitutive model and damage evolution equation are programmed by FEM；and comparison between laboratory data and numerical results are given. Furthermore，the numerical code is applied to the simulation of creep and damage behaviors of underground salt caverns during natural gas injection and pumping. The creep damage evolution zones of the caverns are obtained from the numerical analysis. The achievements from the research work can provide references to the design of Jintan Underground Gas Storage.

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EXPERIMENTAL STUDY ON RELATIONSHIP AMONG PERMEABILITY，STRAIN AND BEDDING OF SOFT ROCK

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2007, 26 (3): 473-473 doi:

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In civil engineering，hydraulic engineering and nuclear wastes disposal engineering，great attention is focused on the influence of stress state on rock permeability. The permeability coefficients of clayey siltstone and brown mudstone were investigated by the transient pulse technique in the complete stress-strain curve. The results show that：(1) The permeability coefficient of clayey siltstone decreases in the stage of elastic deformation but increases in the stage of plastic deformation and the fractured phases. The permeability coefficient on the direction vertical to the bedding plane is larger than that on the direction parallel to the bedding plane. (2) The permeability of brown mudstone decreases in the stage of plastic deformation but keeps stable in the stage of creep deformation. The permeability coefficient on the direction vertical to the bedding plane is similar to that on the direction parallel to the bedding plane. Combined with the stress-train curves，it can be deduced that in the stage of elastic deformation，the permeability coefficient of clay siltstone is mainly influenced by porosity and small cracks；and in the stage of plastic deformation and the fractured phases，it is mainly influenced by small crack. In the complete deformation process，the permeability coefficient of brown mudstone is influenced by porosity and small cracks，boty effects are not distinguishable.

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ANALYSIS OF ENERGY FOR ROTARY DRILLING IN WEATHERED GRANITE FORMATION

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2007, 26 (3): 478-478 doi:

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Rotary drilling is a dominant way in geotechnical engineering borehole surveying. Based on the principle of conversation of energy，the energy for rotary drilling has been analyzed. Besides，a hydraulic rotary drill R–20 instrumented with a drilling process monitoring(DPM) system has been used for site investigation on weathered granite formation；and drilling energy is further analyzed based on the monitored data. The result shows that the penetrating energy in drilling is mainly kinetic energy dependant. The distribution of energy for rock failure is related with the strength characteristics of the penetrated formation. The kinetic energy is more than 98 percent and energy from effective thrust force is less than 2 percent when drilling in slightly weathered rock or fresh rock. However，the energy from the effective thrust force reaches to more than 22 percent，apparently increases with the increase in weathered degree of rock when drilling in soil or very strongly weathered rock. It shows that kinetic energy of drilling system and energy of effective thrust force can reflect the characteristics of the penetrated formation，which can provide theoretical foundation for identification of formation using penetrating energy in real-time.

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CT REAL-TIME SCANNING TESTS ON ROCK SPECIMENS WITH ARTIFICIAL INITIAL CRACK UNDER UNIAXIAL CONDITIONS

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2007, 26 (3): 484-484 doi:

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The crack propagation mechanism of the rock-like material that is carefully selected through comparison of similar physico-mechanical parameters is studied. The CT real-time scanning tests of the rock specimens with artificial single initial disk-like fracture are carried out to study the propagation mechanism of the 3D crack under compression stresses. From CT image analysis，it is preliminarily determined that the failure of the specimens is caused by the damage evolution of the crack. From the comparative analysis of CT values and CT variances in manifold areas，some valuable information and important parameters are obtained with increasing load as follows：(1) the courses of compressed crack；(2) self-similar propagation；(3) wings growth；(4) micro-cracks propagation；(5) cracks joining；(6) cracks accelerated growth；(7) damage evolution course of the specimen failure and the parameters of initial propagation strength；(8) propagation length of wing crack；and (9) self-similar propagation length of crack，etc.. The stress-strain curve is divided into four sections before failure of the specimen，and damage propagation mechanisms of initial fracture is given.

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NUMERICAL SIMULATION OF 3D COUPLED THERMO-HYDRO- MECHANICAL ANISOTROPY OF ARGILLITE ROCK FOR RADIOACTIVE WASTE DISPOSAL

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2007, 26 (3): 493-493 doi:

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For better understanding of thermo-hydro-mechanical coupling processes of argillite rock in Mont Terri project site during the long-time radioactive waste disposal，coupled fields of temperature，pore pressure and stress are studied during the heating and cooling phases with the theory of porous media mechanics. The anisotropy of thermo-hydro-mechanical behaviour is considered simultaneously during the calculation. The influence of the variation of water viscosity due to temperature variation on permeability of pore water is also considered during the simulation. The whole process of excavation，heating phase and cooling phase have been simulated in the calculation；and the calculated results are analyzed. It indicates that the anisotropy of thermo-hydro-mechanical behaviour of the argillite rock is the main factor affecting temperature distribution，pore pressure and stress fields. By comparing the simulated results of coupled isotropic model and anisotropy model，it is shown that the numerical results of coupled anisotropy model can objectively describe the coupled thermo-hydro-mechanical effect of the argillite rock located in the underground rock laboratory with thermal load. The simulation results also indicates that the argillite rock undertakes the compressive stress during the heating phase，while it undertakes tensile stress locally during the cooling phase；and these tensile stress maybe induce the generation of cracks in the rocks.

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FRACTAL DIMENSION OF ORIENTATION POLE DISTRIBUTION FOR ROCK MASS JOINTS

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2007, 26 (3): 501-501 doi:

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Orientation distribution of rock mass joints has been studied by scholars for about four decades，but the features of joint orientation distribution are still not easy to be described，because the orientation is distributed in the bivariate manner；and it is difficult to be used in the rock engineering. The method to combine the idea of box-counting method by Benoit Mandelbrot with the skill of lower hemisphere Schmidt equal area polar plot and the dynamic box-counting method by a computer program is employed to study the features of joint orientation distribution for each cluster. Then the fractal dimension of discontinuities pole on the lower hemisphere Schmidt equal area polar plot is calculated；and the basic regulations of orientation distribution and the relation between the fractal dimension and orientation dispersivity are put forward. The basic regulations of the fractal dimension of the joint orientation pole are that the more poles of the orientation clusters are，the higher value of the fractal dimension is. However，the results are not always the cases；and the fractal dimension values will be different when the values of the orientation ranges are different，even for the same amounts of poles of the cluster orientation. It shows that the higher fractal dimension of the orientation cluster is，the wider range of the orientation value for the cluster is，i.e. the more dispersivity is shown for the cluster orientation.

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DEFORMATION FEATURES OF SHUPING LANDSLIDE CAUSED BY WATER LEVEL CHANGES IN THREE GORGES RESERVOIR AREA，CHINA

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2007, 26 (3): 509-509 doi:

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The Three Gorges dam construction on the Yangtze River in China is the largest hydroelectric project in the world. After the first impoundment in June 2003，many landslides occurred or were reactivated. Shuping landslide is one of the most active landslides among them，which is a reactivated landslide occurred in shale and sandstone of Tertiary period. As soon as the first impoundment of the Three Gorges reservoir was conducted，serious deformation occurred in the Shuping landslide. It formed a large dangerous factor for the local residents and the shipment in the main stream of the Yangtze River. The deformation of the Shuping landslide is monitored by GPS extensometers；and crack measurements are summarized. Based on the monitored data，the deformation features of the Shuping landslide caused by water level changes are analyzed. Also，for the investigation of the groundwater situation，1 m-depth ground temperature measurement was conducted；and the groundwater veins were estimated. It is found that there was no obvious deformation occurred in the head of the landslide. Extension deformation occurred in the upper part，and comparison deformation occurred in the lower part，while the deformation at the middle part was not obvious. As indicated in GPS monitoring results sooner after the impoundment of the reservoir，the lower part has faster displacement rate downward faster than that of the upper part. Currently，the displacement of the lower part was almost terminated while the upper part displaced downward gradually and compressed the lower part at the current water level. Through the investigation on the groundwater and comparison of deformation with rainfall data，it is estimated that the water level change of the Yangtze River is not the only affecting factor for the reactivation of the Shuping landslide. Groundwater condition of the Shuping landslide should also be further investigated.

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DEDUCTION OF FAILURE CRITERION FOR GEOMATERIALS BASED ON MAXIMUM PRINCIPAL SHEAR STRAIN

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2007, 26 (3): 518-518 doi:

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Yield and failure are two different conceptions，and they are two different steps in the deformation processes of materials. In the stress space，the failure surface of perfect plastic materials keeps unchangeable. In the strain space，however，with the constant size of failure surface，its center location moves with the increase of plastic deformation. So the traditional criteria built in the stress space cannot determine whether the material is destroyed. On the contrary，the criteria built in the strain space can properly deal with the problem. The strain criterion for ductile shear failure based on the maximum principal shear strain is established. On the basis of triaxial compression test results of normally consolidated saturated clay，the development laws of stress and volume strain(drained) or pore water pressure(undrained) with strain are analyzed；and the results of numerical simulation with ANSYS are in consistent with the test results. So it is rational to take the shear strain of initial critical state as the limit failure strain. The formulas of the maximum principal shear strain are deduced；and the calculation cases for several commonly used yield criteria are presented.

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STUDY ON FRACTURE PATTERN OF OPEN SURFACE-FLAW IN GABBRO

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2007, 26 (3): 525-525 doi:

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A series of experimental studies are carried out to investigate the propagation of an open surface-flaw in gabbro samples under compression load. A new fracture pattern is observed where an anti-wing crack(its growth direction is opposite to that of wing crack) is induced at a distance away from the flaw tip in the region of compression stress zone. The wing crack appears at the later stage. Besides，the stress for crack initiation is strongly affected by the inclined angle a of the pre-existing flaw. The stress for crack initiation decreases when the flaw angle increases(30°≤a≤75°). Besides，the outburst phenomenon always appears at the flaw tips when the flaw angle equals about 45°，which may be an important parameter for the problem of the rock outburst. The initiation angle of the anti-wing crack is between 135°and 145°from the flaw plane. The growth of the anti-wing crack turns to the loading direction when the crack growth length equals about half of the flaw length. The results of acoustic emission(AE) support the observations from the experiments. The anti-wing crack pattern can be observed in all the specimens containing an open surface-flaw. However，the growth mechanisms of the anti-wing crack are not fully investigated up to now. A further study would be carried out in the future.

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THREE-DIMENSIONAL GRID-BASED STRATA MODEL AND SPATIAL ANALYSIS IN GEOTECHNICAL ENGINEERING

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2007, 26 (3): 532-532 doi:

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The technologies of geographic information system(GIS) and spatial information provide a new method for solving complex problem in geotechnical engineering，where the technology of model construction for strata and caverns in three-dimensional space is a key issue. Analysis of developing spatial three-dimensional strata model will make it possible for GIS to be successfully applied to geotechnical engineering. However，there are few references related to this subject at present. Based on a typical slope project in Longtan Hydropower Station，the technique for model construction of three-dimensional grid strata model which consists of multi-variant information such as monitoring facilities，construction measures and faults，is introduced. In addition，some spatial analysis algorithms such as generation of simple strata cross-section，intersection between strata and three- dimensional objects，hybrid sectional algorithm between strata and cavern，spatial calculation for area and capacity in arbitrary zone are discussed. The proposed technology will give some useful references to the continuous research on this subject.

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STUDY ON COMPUTATION METHOD FOR CASING LOAD INDUCED BY SOFT ROCKS

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2007, 26 (3): 538-538 doi:

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Casing failures are often caused by the rheological load generated by the soft rocks in China，which give rise to large economical loss. Based on the theory of the viscoelastic rheological model，the coupled mechanical model of the soft rocks，the concrete sheath and the casing is developed. Hence，the equations to compute the rheological load of casing and concrete sheath under the uniform in-situ stress are derived according to the analysis of constitutive law，geometric deformation compatibility，and static equilibrium. The software is developed；and the correlation between the casing load and the rheological parameters of the soft rocks，initial creep of the wellbore，mechanical properties of the concrete sheath is obtained. The results indicate that the rheological mechanical properties of the soft rocks，initial creep of the wellbore，mechanical properties of the concrete sheath have large effects on the casing load；and initial creep of the wellbore can reduce the rheological load and decrease the casing stress；however，no concrete sheath in the annulus can undergo the casing service life because the concrete sheath can increase the casing stress. The achieved results are coincident with the field data，which are already used for cementing and casing design in the Jianghan Oilfield，China.

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STUDY ON PACKING BODY SUPPORTING RESISTANCE OF ENTER-IN PACKING FOR IN-SITU GOB-SIDE ENTRY RETAINING IN FULLY- MECHANIZED TOP-COAL CAVING MINING FACE

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2007, 26 (3): 544-544 doi:

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Based on the technique of in-situ gob-side entry retaining with entry-in packing in fully-mechanized top-coal caving mining face(GEREPTF)，the mechanical model of the surrounding rock for GEREPTF is established according to the key strata theories. Based on these theories，the reasonable calculation formulas of the packing body supporting resistance are presented. According to the different field conditions，the interaction relationship between the packing body and the surrounding rock is also studied. The results show that the surrounding rock stability is closely related with the packing body and the entry support method. The adoption of bolting with bar，wire meshes and cable support techniques in the entry combined with the technical measures of timely packing and strengthening temporary support can guarantee the integrity of the entry. Thus the packing body and the surrounding rock can formulate a good and corporate carrying capacity system. It can improve the bearing capacity of the surrounding rock；so the necessary packing body supporting resistance can be greatly reduced. The successful field industrial test proves that the GEREPTF technique and its corresponding mechanical model and calculation formulas of the packing body supporting resistance can be adopted for the convenience and rationality，which can be employed for similar fully-mechanized top-coal caving mining face.

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DIGITAL IMAGE BASED CHARACTERIZATION METHOD OF ROCK¢S HETEROGENEITY AND ITS PRIMARY APPLICATION

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2007, 26 (3): 551-551 doi:

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A digital image based characterization method of rock¢s heterogeneity is developed according to the theory of digital image processing. In the proposed method，digital image processing method is used as a measurement tool to represent the actual spatial distribution of different materials and components in the rock samples. The heterogeneity described by this method is approaching to the actual heterogeneity of rock，which is mapped into the grid of finite element method(FEM). This characterization method is incorporated into rock failure process analysis(RFPA) code；and a numerical model that can actually reflect rock¢s heterogeneity is established，which overcomes the shortage that statistic theory is used to describe the heterogeneity of rock in traditional FEM. By simulating two regular laboratory tests(uniaxial compression and uniaxial tension tests)，real failure processes of granite are visually observed. The simulation results show that heterogeneity of rock has a great influence on its mechanical function and failure processes. This model provides an innovative method for the investigation on mechanical feature and failure mechanism of heterogeneous material such as rock，concrete and so on.

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EXPERIMENTAL STUDY ON DYNAMIC STRENGTH OF MUNICIPAL SOLID WASTE

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2007, 26 (3): 560-560 doi:

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To study the dynamic strengths of municipal solid waste(MSW)，the dynamic triaxial tests on artificial MSW samples were performed by using moderate-scale dynamic triaxial apparatus. It was found that the dynamic pore water pressure was considerably dependent on the dynamic strain. When the cyclic number exceeds a certain value，the dynamic pore water pressure of MSW will approach to a steady state；and the liquefaction was not found in vibration process. Based on the different strain failure criteria and the equivalent cyclic number，the dynamic strength parameters are obtained，which can be used in dynamic stability analysis of landfill. The dynamic strength curve of MSW has good normalization behavior；and through some representative tests，the expression of dynamic stress-strain relation of any equivalent cyclic number is achieved for different initial stresses，which can offer calculation formula and test parameters for estimating seismic settlement.

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FORMULATION MECHANISM OF HALF-WHITE BLACK CIRCLE IMAGES OF ROCK DENSITY DAMAGE INCREMENT WITH CT AND ITS REGISTRATION AND CORRECTION

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2007, 26 (3): 567-567 doi:

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Rock density damage increment with CT can be obtained by subtracting CT number of the undisturbed rock samples from that of the loaded rock samples. However，the special phenomenon may come into being when density damage increment data are translated into grey images. In such CT images，the circular contour line of rock samples is divided into two half circles. The half circle is white，and the other one is black. Such contour line of rock samples is called half-white black circle in this paper. In order to discover the information mechanism of the phenomenon，a group of CT test data，which are from the same scanning section of a sandstone sample at the four different stress steps，are used to analyze the CT number distribution. The analytical results show that there is the small offset between CT images，which is the reason that the half-white black circle phenomenon can be found in density damage increment images. After the small offset is corrected by registration processing，this phenomenon disappears.

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EXPERIMENTAL STUDY ON SHEAR BEHAVIORS OF BRITTLE MATERIALS UNDER CYCLIC LOADING

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2007, 26 (3): 573-573 doi:

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Shear tests under static and cyclic loadings were performed with direct shear equipment in order to explore the shear behaviors of brittle materials such as concrete，rock，etc. under different loadings. The direct shear equipment that allows static and dynamic shear tests，was designed based on MTS in the Vibration Laboratory of Hohai University；and brittle materials were modeled by mortar. Test results under static and cyclic loadings including 1，2，3 and 5 Hz show： (1) shear stress-displacement curves under static loading are similar to the strength envelope curves under cyclic loading that can be divided into four parts；(2) the peak strength and residual strength under cyclic loading are larger than those under static loading when other conditions were same，but they change inconspicuously with the frequency changes；(3) peak strength and residual strength increase with normal stress increase under both loading conditions；(4) failure strains under static loading are larger than those under dynamic loading and both increase with the normal loading increasing；and (5) shear dilatancy is obvious during the shearing process. The failure mechanism was described simply at last.

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CENTRIFUGAL MODELING TEST STUDY ON HIGH-EMBANKMENT WIDENING OF HIGHWAY

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2007, 26 (3): 580-580 doi:

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Based on the project of high-embankment widening of highway，the water content and degree of compaction of foundation soil，filling and improved soil by lime were determined by means of indoor physico- mechanical test. The centrifugal modeling tests were used to simulate increasing degree of compaction and improve soil by lime for coordinating deformation between new and old high-embankment widening. The test results show that the deformation of high-embankment widening was decreased，but differential settlement was not controlled effectively when the degree of compaction of high-embankment widening was increased to 93%，94% and 96% from 90%，93% and 95% correspondingly. Then both deformation of high-embankment widening and differential settlement were decreased when the filling was improved by 6% lime mixture；and the effects of deformation compatibility of high-embankment widening were enhanced. The in-situ monitoring data agree well with the results of centrifugal modeling test.

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APPLICATION OF FIBER BRAGG GRATING SENSING TECHNOLOGY TO TUNNEL MONITORING

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2007, 26 (3): 587-587 doi:

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On the basis of introducing the basic principle and advantages of fiber Bragg grating(FBG) sensing technology，the layout schemes of FBG and temperature compensation technology in the Bainijing Tunnel No.3 in Kunming City are put forward. After 24-hour continuous monitoring，the influence of daylong maximal difference in temperature on the changes of the Bragg wavelength is discussed；and reliability estimation of the Bragg wavelength obtained by temperature sensing system on each monitoring tunnel cross-section is carried out. The calculation results validate the reliability of the FBG measurement system as a result that the standard errors of the Bragg wavelength are less than 14 pm. Then，the eight-month strain monitoring data illuminate that alternation of dry season and rainy season as an important factor is the reason in strain fluctuation of monitoring spots and rainy season as the main reason for the increase of strain change. Finally，an important monitoring position is determined；and the secondary lining of the tunnel is stable at present. The achieved results show that the FBG is good at measuring strain distribution of tunnels due to its excellent characteristics compared with traditional electromotive sensors and other optical fiber sensors. As a result，it is a feasible and effective method for structural health monitoring and damage detection of tunnels.

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COMPARATIVE ANALYSIS OF STRATA PREDICTION MODELS FOR GROUND MOVEMENT INDUCED BY TUNNEL CONSTRUCTION

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2007, 26 (3): 594-594 doi:

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Stochastic medium method(SMM) and Peck method are widely used in the field of ground movement induced by urban soft ground tunneling in China. However，little is known on their relations of theoretical background，the application conditions，and how to evaluate the results from these two methods. Besides，the determination for the key parameters for SMM is also a problem because of the relative little experience from the engineering application in China. Based on the theoretical background study and case study analysis，the theoretical relationship between SMM and Peck method is discussed；and one of the main conclusions is that Peck method can be regarded as a simplification of SMM，but they both are suitable for relatively deeper excavation condition. However，Peck method is not acceptable for the ultra-shallow tunneling where the specific conditions are expected to cause considerable large errors. Although the Peck method is feasible in most urban tunneling conditions，the SMM has a broader application against Peck method in terms of its theoretical background. The relations between the parameters of these two methods are also studied；and some simple but efficient methods for the determination of the parameters have been proposed. The suggested methods are proven and verified by many practical engineering projects；and they can significantly improve the adaptability of SMM in engineering application.

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EXPERIMENTAL STUDY ON RHEOLOGICAL ENGINEERING PROPERTIES OF COARSELY GRANULAR RED SANDSTONE SOIL

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2007, 26 (3): 601-601 doi:

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In order to analyze the rheological properties of coarsely granular red sandstone soil in the highway embankment engineering，a series of rheological experiments were conducted on the rheological device that was developed by the authors. Through these rheological experiments，the rheological properties，the main factors affecting the coarsely granular red sandstone soil¢s rheological properties and a rheological model of the coarsely granular red sandstone soil were studied. The experimental results show that the principal stress was the main factor that affects the rheological strain action. According to these rheological tests data，creep curves under the low principal stress conditions(s ≤0.8 MPa) display the linear viscoelastic rheological properties；while creep curves under the high principal stress conditions(s＞0.8 MPa) show the nonlinear viscoelasto-plastic rheological properties. The linear viscoelastic rheological model(Burgers) can describe the linear rheological properties well. At the same time，Burgers rheological model parameters are identified by the modified least square algorithm with the test data. The test data show that the Burgers rheological model can describe the linear rheological properties，including the declining rheological phase and stable rheological phase as well，but can not describe the nonlinear rheological properties，especially the accelerating rheological phase. According to the nonlinear viscous elastoplastic rheological properties，a new viscoplastic rheological body(VPB) model based on hyperbolic function is put forward to describe the accelerating rheological phase of coarsely granular red sandstone soil under the high principal stress conditions. Then，a new 6-element nonlinear viscoelasto-plastic rheological body(VEPB) model is set up by putting the new viscoplastic rheological body model and the Burgers model. According to the rheological test data，the parameters of the VEPB are identified by the modified least square algorithm method. During the rheological tests，there is a good agreement between the creep test curves and the VEPB rheological model¢s creep curves，which is testified that the VEPB model is reasonable and the viscoelasto-plastic rheological Burges model could describe all rheological phases of coarsely granular red sandstone soil including the accelerating rheological phase.

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STUDY ON BLOCK ELEMENT METHOD FOR DYNAMIC ANALYSIS

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2007, 26 (3): 608-608 doi:

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Dynamic analysis of structures is one of main issues of structural design，especially for structures of rock masses containing various discontinuities. Numerical analysis is an important method for the problem. Block element method(BEM) is an effective numerical method for the analysis of rock masses. BEM is employed to expand the dynamic analysis of structures. At first，the formulas of mass matrix and damping matrix for dynamic analysis of BEM are presented；then，the dynamic equilibrium equations of the block system subjected to the inertia forces，the damping forces，the dynamic loads and the elastic forces are formulated. Finally，two examples are studied with the method. Both of the results are very close to those calculated by other methods. BEM has advantages in pretreatment of large numbers of discontinuities contained in rock masses；so it is expected to be widely used in stability analysis of complicated rock masses under dynamic or seismic loadings.

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EXPERIMENTAL STUDY ON TEMPERATURE AND RESPONSE OF SEASONAL ACTIVE LAYER OF TUNNEL¢S SURROUNDING ROCK IN PERMAFROST REGION ON QINGHAI—TIBET PLATEAU

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2007, 26 (3): 614-614 doi:

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The excavation of tunnel will affect the thermal stability of surrounding rock in permafrost region. Accordingly，an active layer close to the supporting system of tunnel is formed in the surrounding rock under seasonal thawing and freezing. Based on the excavation of Fenghuoshan Tunnel of Qinghai—Tibet Railway，a detailed experimental investigation is conducted. Some useful conclusions of the active layer¢s thermal regularity are achieved. First，an important fact of in-situ experiment is that temperature of frozen rock behind the liner varies with time and space linearly. Second，another interesting phenomenon is that thawing depth of surrounding rock surpasses the natural thawing depth of this region during construction period. For instance，some areas¢ thawing depths are found below 5 m，while the natural value of this region is only 1.36–2.11 m. Analytical result indicates that the temporary heat produced during excavation causes the additional thawing of frozen rock/soil behind liner，such as chamber blasting，machine operating，construction illuminating，and so on. According to the in-situ data，regression analysis shows that the ratio of thawing depth value during construction and its natural thawing value of this region vary with the ratio of atmospheric temperature inside to outside of the tunnel linearly. Finally，the achieved data illustrate that thawing depth is less than that of the region¢s natural value after tunnel excavation，which is deemed as a vital fact：the special insulating layer which is set between the primary support and the liner structure. Similarly，regression analysis shows that the ratio of thawing depth after excavation to its natural value changes with the ratio of atmospheric temperature inside to outside of the tunnel linearly，i.e. the atmospheric temperature in the tunnel refers to surface temperature of surrounding rock，where temperature monitoring units are installed on the surface of the primary support behind insulating layer.

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STUDY ON INTERVAL NONLINEAR FUZZY JUDGMENT METHOD OF ROCK MASS CLASSIFICATION

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2007, 26 (3): 620-620 doi:

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Aiming at localization and deficiency of existed fuzzy classification methods for rock mass quality in underground structures，the nonlinear weighting operation of fuzzy matrix as well as the interval feature of the weight vector and membership of the factors for the rock mass classification are specially studied considering the properties of the fuzziness and grade of factors. Moreover，by using nonlinear fuzzy matrix composition operator and interval mathematical theory along with the analytical method of relative superiority of the interval number matrix，the interval nonlinear fuzzy judgment method for rock mass classification is established，which can reduce the judgment subjectivity and enhance the influences of the adverse factors on the judgment results. So the method makes the rock mass classification much more rational and easier to operate. The computation results of practical engineering and its comparison with those of other classification methods show that it is reliable and reasonable.

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DYNAMIC ANALYSIS METHOD OF SLOPE STABILITY BASED ON LURR THEORY

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2007, 26 (3): 626-626 doi:

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The theory of load-unload response ratio(LURR) is introduced to analyze dynamic slope stability. The LURR model of slope is established by studying laws of load-unload response ratio of slope under seismic load；and a concept of load-unload response degree(LURD) is suggested to substitute the factor of safety. With this concept，a new method of dynamic slope stability is explored；and deformation analysis and stability evaluation are well combined. Taking the right bank of Majiayan reservoir for example，a dynamic analysis is performed using the suggested method. Compared the calculating results with pseudo-static method，finite element method and Newmark sliding block method，it is verified that the presented method is reasonable. The new method has priority to traditional dynamic analysis method in precision；and it can carry out deformation and stability analysis at the same time.

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APPLICATION OF GREY-NEURAL NETWORK MODEL TO LANDSLIDE DEFORMATION PREDICTION

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2007, 26 (3): 632-632 doi:

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According to the monotonously increasing characteristics and the nonlinear characteristics of landslide displacement time series，the displacement of landslide is decomposed into trend item and random item based on the responding composition model. The trend and random items of displacement time series are predicted by grey-neural network model；and the implementation process of grey-neural network model is discussed. As an example，the grey-neural network model is applied to the prediction of the short-term displacement of Maoping landslide based on the in-situ displacement data. The reasonable result shows the validity and feasibility of the grey-neural network model for landslide displacement prediction.

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DISCUSSION ON“NONLINEAR VISCOELASTO-PLASTIC RHEOLOGICAL MODEL(HOHAI MODEL) OF ROCK AND ITS ENGINEERING APPLICATION”

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2007, 26 (3): 637-637 doi:

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REPLY TO “DISCUSSION ON‘NONLINEAR VISCOELASTO- PLASTIC RHEOLOGICAL MODEL(HOHAI MODEL) OF ROCK AND ITS ENGINEERING APPLICATION’”

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2007, 26 (3): 641-641 doi: