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2008, 27 (11): -0 doi:
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2008, 27 (11): -2161 doi:
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SURFACE RUPTURE AND HAZARD CHARACTERISTICS OF WENCHUAN EARTHQUAKE WITH MAGNITUDE 8.0 IN SICHUAN PROVINCE

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2008, 27 (11): -2173 doi:
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On May 12 of 2008，the Wenchuan M8.0 earthquake in Sichuan Province occurred on the Longmenshan tectonic belt at the eastern margin of the Qinghai—Tibet Plateau. Through field investigation and survey，the major surface rupture occurred on the segment of Beichuan—Yinxiu fault from the southwest of Yingxiu to Shikanzi of Nanba in Pingwu County，with a length of 220 km. It shows the fault produces a thrust and dextral slip. The maximum displacement along the fault is about 6 m；horizontal component is equivalent to the vertical direction. Another segment from Xiange in Dujiangyan City to Sangzao in Anxian County produces a 100 km coseismic surface rupture in length，also displaying a thrust and dextral characteristic of the fault. The maximum vertical displacement on this segment is about 2 m；and the ratio of the vertical component and the horizontal is between 1∶3 and 1∶1. The distribution of surface rupture and the characteristics of coseismic displacements show that the thrust-dextral slip of Beichuan—Yingxiu fault led to the Wenchuan M8.0 earthquake，representing strong ground motion destroy，surface cracking directly and secondary geological hazards(such as landslip，hillside creep) pulling down or burying the civic structures. Based on macroscopical survey，studies of InSAR，and records of seismographs，the axis of isoseismal line extends at N40°–50°E orientation along the Longmenshan tectonic belt. Its typical characteristic is a unilateral，multipoint instantaneous rupture. The earthquake produced three intensity damaged areas with seismic magnitude XI，and remarkably enhanced the damages of normal earthquake attenuation in the North Sichuan province，the South Gansu Province and Hanzhong region of Shaanxi Province.

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RESEARCH ON TRANSIENT CHARACTERISTICS OF EXCAVATION UNLOADING

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2008, 27 (11): -2184 doi:
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On the basis of the analysis of process of excavation unloading and the calculation of its releasing duration，it is shown that the excavation unloading during rock blasting is a transient process under middle to high in-situ stress conditions. It is proposed that the transient characteristics of the excavation unloading and correspondingly induced dynamic responses of surrounding rock should be considered under middle to high in-situ stress conditions. Problems such as the determination of divisional excavation unloading corresponding to millisecond delay initiation，the path of transient releasing of excavation unloading，releasing of excavation unloading-induced vibration and the mechanism of dynamic loosening of jointed rock mass induced by the transient unloading of in-situ stress，etc. are also discussed. Finally，two historical cases of excavation unloading-induced vibration and dynamic failure of jointed rock mass in Pubugou and Ertan Hydropower stations are presented as verifications.

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FITTING AND EVALUATION OF TEST DATA USING UNIFIED STRENGTH THEORY

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2008, 27 (11): -2193 doi:
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Unified strength theory is the development of Coulomb criterion with analyzing the effect of intermediate principal stress. It deems that rock has the same strength under conventional triaxial compression and tension；and a zigzag is used to describe the effect of intermediate principal stress on strength. The theory has been studied deeply and used widely. The true triaxial strengths of eight rock samples using the theory are fitted；and the processes of parameters determination and misfits of the fitting solutions are also given. If the parameters of Q and K are determined from the relationship between pseudo-triaxial strength and confining pressure，and only parameter b is determined from true triaxial strengths，the theory can not describe main characteristics of the influence of intermediate principal stress on strength. The misfits for several rock samples may be higher than those from Coulomb criterion. If the parameters of Q，K and b are determined on the least misfit to the whole set of strengths，the theory has a pretty fitness. However，the pseudo-triaxial strengths of several rocks from the best fitting solutions have great scatterness from the real magnitudes. Also，it does not correspond to the experimental results that rock has the same strength under conventional triaxial compression and tension；the maximum increase of strength from intermediate principal stress has a linear relation with the minor principal stress；and the first-order derivative of strength has an interruption at the peak point. Insufficiency of experimental results and dispersion within test data make great difficulty in reviewing the feasibility of the best fitting solutions.

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EXPERIMENTAL RESEARCH ON MECHANICAL PROPERTIES OF GRANITES UNDER UNLOADING CONDITION

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2008, 27 (11): -2205 doi:
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Based on unloading tests of rock samples，the deformation，parameters and fracture features of rocks under unloading are studied. The test results show that：(1) The characteristics of intense rebound deformation，distinct dilatancy and brittleness failure of rocks are all shown in the process of unloading. (2) Deformation modulus E gradually decreases and Poisson ratio m increases in the process of unloading. The deceasing amount of E is 5%–27%，while m increasing 50%–335%. The variables all increase with initial confining pressure increasing and unloading intensity，which are related with volumetric strain. (3) The cohesion c decreases but the internal friction angle increases relatively with the loading tests，and both are less with unloading intensity. The peak value of c decreases 33.2%–47.8%，and remains normal value of 65.3%–77.6%；peak value of increases 14.7%–33.2%，and remains normal value of 5.9%–9.4%. (4) The fracture is characterized by strong tensile，and all tensile cracks are fully developed，showing hypo-unloading when the rock samples are unloaded in two directions；and the shear fractures expand following tensile cracks.

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POWER FUNCTION BASED MOHR STRENGTH CRITERION FOR MARBLE WITH UNLOADING CONFINING PRESSURES

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2008, 27 (11): -2214 doi:
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Conventional triaxial test and pre- and post-peak unloading confining pressure tests of marble have been performed. Mohr stress circles under different confining pressures and envelopes are achieved. The results indicate that linear Mohr envelope can not match stress circle very well；and the Mohr-Coulomb criterion describing marble strength will bring large error. In order to solve the problem，a nonlinear Mohr strength criterion is proposed，i.e. power function Mohr strength criterion，to fit the test data and compare the theoretical values and test values. The failure curve of power function Mohr strength criterion in p plane is presented；and the failure curve of Mohr-Coulomb strength criterion is then compared. It is shown that the power function of Mohr strength criterion can describe marble strength much better.

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RESEARCH ON CHARACTERISTICS OF CORAL REEF CALCAREOUS ROCK IN NANSHA ISLANDS

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2008, 27 (11): -2221 doi:
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Mechanical properties of calcareous rock become one of the new research issues in geotechnical engineering while embarking upon ocean resources exploitation and marine works construction. Physico- mechanical properties of calcareous rock samples，which are taken from Yongshu and Zhubi coral reefs in Nansha Islands in South China Sea，are tested. The tests include ultrasonic wave test，uniaxial tensile strength test，uniaxial compression strength test，and triaxial compression strength test. The results show that the porosity of calcareous rock is much larger than that of other rocks；and the longitudinal elastic wave velocity is linearly decreased with the increase of porosity. Longitudinal elastic wave velocity is between 2 700 m/s and 3 700 m/s. The difference of dry and saturated tensile strengths is not evident；and the results show that the strength of calcareous rock does not decrease when it is saturated by water. Calcareous rock is brittle but it is different from granite. Multi-fracture planes emerge along the growth line of coral when breakdown occurs and it keeps considerably high residual strength. It is found that the damage pattern is determined by lithologic frame of calcareous rock.

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SUSCEPTIBILITY ANALYSIS OF DEBRIS FLOW TO ROCKS BASED ON HYDROLOGICAL CHARACTERISTICS OF THEIR
WEATHERING PRODUCTS

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2008, 27 (11): -2227 doi:
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The susceptibilities of debris flow to different rocks vary obviously；and the Xiaojiang River basin is taken as a case study to analyze the susceptibilities of debris flow to different rocks. Nineteen samples of weathering products of 9 kinds of rocks with different elevations and five samples of debris flow depositions are collected in five debris flow valleys in upper，middle and lower reaches of the Xiaojiang River basin. The hydrological characteristics of each sample are analyzed by liquid and plastic limits and permeation experiments. Three indices of hydrological characteristics，such as plastic limit wP，plastic index IP and permeability coefficient KT，are selected；and the Euclidean distance is employed to analyze the susceptibilities of debris flow to different rocks based on the hydrological characteristic analysis of the samples. According to the analytical results，the order of the susceptibilities of debris flow to these nine kinds of rocks in increasing sequence is as follows：basalt，argillaceous limestone，dolomite，slate，Quaternary deposit，sandstone，siltstone，phyllite and mudstone. In order to check this order，the susceptibilities of debris flow to rocks of various valleys in Xiaojiang River basin are calculated based on the results of susceptibility analysis. According to the susceptibilities of all valleys and distributions of debris flow valleys in Xiaojiang River basin，the susceptibilities of debris flow to different rocks are reasonable；and it may be helpful for the assessment of debris flow hazards and prediction of debris flow.

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RESEARCH ON CAVING CHARACTERISTICS OF SHIZHUYUAN POLYMETALLIC MINE UNDER MULTI-MINED-OUT-
AREA CONDITIONS

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2008, 27 (11): -2234 doi:
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The Shizhuyuan polymetallic mine is mining by room-and-pillar open stope method for more than 10 years. After 36 designed rooms are mined out，there left 260×104 cubic meters mined-out areas with 8 000 square meters of the maximum continuous exposed face of roof without filling for some reasons. For the sustainable mine development and the safe mining，one main issue is how to management of multi-mined-out-area and the pillar mining. After comparison of many calculation methods，the caving method is chosen. Some useful results are achieved as follows. (1) After the proper evaluation of engineering geology with RMR，Q，MRMR and GSI systems，the mechanical parameters of rock mass are derived by generalized Hoek-Brown failure criterion. (2) After the stability of residual pillar is calculated by Bieniawski method，many mining schemes for the determination of mining method are modeled by three-dimensional elastoplastic finite element method. Based on the modeling and analytical results，the caving method is finally selected. (3) Caving areas for each stage of caving mining is figured out by the latest Laubscher caving stability graph method and extended Mathews stability method. (4) Strata displacement parameters such as caving angle are determined by the radial basis function neural network；the height of cushioning layers for different mined-out-areas is established. (5) For the purpose of safety mining，the ground pressure monitoring system such as acoustic emission，displacement and pressure that are suitable for the hard rock mining are designed and installed. The technological routes of the ground monitoring and an early warning case are also listed，which are proven to be successful with practical data.

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RELATIVE PERMEABILITY LAW OF MULTIPHASE SEEPAGE UNDER HIGH TEMPERATURE AND PRESSURE IN A GAS CONDENSATE RESERVOIR

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2008, 27 (11): -2244 doi:
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[PDF 312 KB] (1994)

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It is most important for modeling the flow state to obtain the representative relative permeability curves of condensate oil/gas，oil/water and gas/water，which are the basic curves most commonly used in numerical modeling and well testing analysis. The fluid flow accompanies the phase change during the reservoir development in a gas condensate reservoir with high temperature and high pressure. Therefore，the relative permeability of the traditional testing with analog oil and gas can not be used for replacing the relative permeability obtained under the reservoir. Based on the analysis of the physical properties of the reservoir rocks and fluid properties，the seepage law of the multiphase is researched under the reservoir temperature and pressure with the condensate oil and gas of the Tazhong oil field in Tarim basin；and the relative permeability curves of condensate oil/gas，oil/water and gas/water are obtained. The results show that the two-phase flow of the oil/water，oil/gas and gas/water will not appear in low porosity and permeability rock；and the two-phase flows of the oil/water，oil/gas and gas/water have large flowing areas and high displacement efficiencies in high porosity and permeability fractured reservoir under the reservoir temperature and pressure. These results offer a very important basic data to simulate or predict the performance of a gas condensate reservoir with high temperature and high pressure.

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RESEARCH ON MECHANICAL PARAMETERS OF SUBCLASSIFICATION ROCK MASS OF HIGHWAY TUNNEL

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2008, 27 (11): -2252 doi:
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The surrounding rock classification is under discussion in the code for design of highway tunnel，and it can not satisfy the construction requirements. Therefore，the subclassification of surrounding rock is performed. Based on the subclassification，the physico-mechanical indices of rock subclassification are achieved. Firstly，based on the subclassification methods，the combination of rock masses with different hardnesses，tectonic structural planes and structural planes combination degree is presented. Numerical experiments on every combination are also performed. Using the experimental results，in-situ investigation and statistical analysis，certain physico-mechanical indices of subclassification rock mass are gained. As for the soil surrounding rock，two ways，i.e. field test and investigation，and statistics analysis，are employed to evaluate the physico-mechanical indices of surrounding rock masses；and then，the laboratory physico-experimental results are combined to determine the actual physico-mechanical indices of soil surrounding rock masses.

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EFFECT OF RAINFALL INFILTRATION ON STABILITY OF MUDSTONE-SOIL MIXTURE EMBANKMENT

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2008, 27 (11): -2260 doi:
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Rainfall infiltration into mudstone-soil mixture embankment is one of the most important factors affecting slope stability. In order to understand the landslide mechanism of mixture embankment induced by rainfall infiltration，the artificial rainfall simulation tests are carried out on a typical highway mudstone-soil mixture embankment of Jiyuan—Shaoyuan expressway. Some field variables of embankment slope during the rainfall are monitored，such as pore water pressure，stress state，deformation and surface displacement of soils. The influences of mudstone-soil mixture embankment slope stability due to rainfall infiltration are discussed. The initiation and formation mechanism of landslide are researched and the trends of development of the slope stability are also evaluated. The field monitoring results and numerical analysis both show that the deformed zone of mudstone-soil mixture landslides caused by rainfall infiltration lies under the slope，and the maximum deformation value appears on the slope surface. The crack makes the rainfall easily get into the deep soil layer，and thus a retaining water layer under slope surface will emerge. The layer causes the increase of the pore water pressure and the decrease of the effective stress together with the disintegrative and suction softening of mudstone. The decrease of strength has great effect on factor of safety(FOS) of the embankment slope stability.

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MONITORING AND ANALYSIS OF EFFECTS OF DRAINAGE TUNNEL ON CRUSHED-ROCK SLOPE

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2008, 27 (11): -2267 doi:
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The measured data of the groundwater level，rainfall and the drainage tunnel discharge about the landslide are studied. Compared with the data of the groundwater level monitored by artificial and automatic measures before and after the implementation of underground drainage works，it is shown that the slope groundwater level has declined after excavating the underground drainage tunnel in crushed-rock slope. By analyzing the correlation of the groundwater level and rainfall，it is shown that the rising of the groundwater level is generally lagged behind the rainfall process；and if there has any accumulation rainfall previously，the groundwater level may be raised immediately with the latter strong rainfall，and the landslide will be induced. By analyzing the relationship between the drainage tunnel discharge and rainfall，it presents that the change of the drainage tunnel discharge is basically synchronous with the rainfall. And only when the rainfall is larger than a certain threshold value，the tunnel drainage discharge will increase correspondingly. By studying the changes process both of the drainage tunnel discharge and the groundwater level，it is shown that the increase of the drainage tunnel discharge is earlier than the rising of the groundwater level. Therefore，the maximum height of the groundwater level can be effectively reduced for the drainage role of the drainage tunnel during a rainfall process. The correlation of the groundwater level，rainfall and the drainage tunnel discharge is discussed based on the monitored data；and it is shown that the underground drainage tunnel measures in crushed-rock slope are reasonable and effective. If any similar crushed-rock slope needs to be controlled，the underground drainage tunnel would be a good choice.

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COMPARISON TESTS ON FIELD BIDIRECTIONAL MIXING COLUMN FOR SOFT GROUND IMPROVEMENT IN EXPRESSWAY

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2008, 27 (11): -2272 doi:
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With a review of disadvantages of ordinary deep mixing techniques in China，the bi-directional mixing technique is developed and presented. In order to investigate the improving effect and economic benefits of slurry bidirectional mixing column for soft ground improvement in expressway engineering，comparison tests between bidirectional and ordinary deep mixing column sites were conducted in the same geological condition field of Shanghai—Jiangsu—Zhejiang expressway，Jiangsu Province，China. The strength characteristics of columns and behaviors of the composite ground under embankment filling were analyzed. It is indicated from the in-situ standard penetration tests(SPT) and unconfined compression tests on coring samples taken from the column that the strength along the columns with bidirectional mixing technique is almost uniform，while strength with the ordinary deep mixing method decreases rapidly with depth. The bearing capacity of bidirectional mixing column composite ground is higher than that of ordinary deep mixing column composite ground. At the same embankment height，the load sharing ratio of bidirectional mixing column is higher than that of ordinary deep mixing column. The ground surface settlement and the maximum lateral displacement at embankment toe of bidirectional mixing testing section are less than those of ordinary deep mixing method. It is also shown that the excess pore water pressure caused in bidirectional mixing composite ground during the embankment filling is less than that in ordinary deep mixing ground，which is benefit for speeding up the filling in the bidirectional mixing ground. In addition，the bidirectional mixing technique can eliminate grout spill phenomena，decrease the disturbance to surrounding soil and save construction time. The results show that bidirectional mixing technique is an efficient and economic method for soft ground improvement in expressway engineering.

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A 3D DETERMINISTIC MODEL BASED PROBABILISTIC METHOD FOR LANDSLIDE HAZARD ASSESSMENT OF LARGE MOUNTAINOUS AREA

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2008, 27 (11): -2281 doi:
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In order to quantitatively assess landslide hazard of a large mountainous area，a slope-unit-based probabilistic methodology that involves a three-dimensional(3D) deterministic model coupled with a geographical information system(GIS) is proposed. An automatic method is developed to divide a study area to slope units. For each slope unit，a GIS-based 3D slope stability analysis model is applied to the calculation of the distribution of 3D factor of safety through a Monte Carlo simulation for the unknown shape of slip surface. Assuming the resultant 3D factor of safety follows a log-normal distribution，a widely-used reliability index is then used to quantitatively evaluate the probability of unsatisfactory performance of each slope unit. At the same time，the location and the magnitude of critical slip surface(s) can also be identified by minimizing the trial 3D factor of safety. An advanced GIS is developed to efficiently implement all of the computational procedures. This method integrates the advantages of both 3D deterministic model and probabilistic method，which can quickly and efficiently complete a large number of 3D modeling and calculations of factors of safety，realizing the quantitative assessment of a natural mountainous area with complexly topographical and geological conditions. The effectiveness of the proposed method has been tested in a practical application to a landslide-prone road slope area in Japan.

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QUANTITATIVE EVALUATION OF HOUSE DEFORMATION AND CRACKS CAUSED BY TUNNEL-CROSSING

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2008, 27 (11): -2288 doi:
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House cracks and over-deformation are hot issues in tunnel-crossing urban territory，and related studies of calculation of house cracks and its risk evaluation lag far behind the needs of engineering. Based on practice of Xiamen Airport Road Tunnel-crossing building blocks，house deformation and cracks can be quantitatively calculated and explained with W-W failure criterion，Mazars damage model，and yield approach index(YAI) model. By comparison，results show that YAI model is essentially one kind of generalized plastic zone；and its result is distribution of safety degree of house cracks. And Mazars damage model is typical tensile damage model，thereby house cracks can be evaluated by the damage factor. Meanwhile，with YAI or Mazars damage model for numerical simulation of tunnel-crossing process，nonlinear relationships between house cracks and tunnel construction process will be nicely established；thus house cracks can be quantitatively evaluated and pre-controlled. As a whole, simulation results of deforming and cracking process have good coincidence with in-situ measured house fractures and deformation.

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TENSION MEASUREMENT OF GEOGRID IN CENTRIFUGAL
MODEL TEST

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2008, 27 (11): -2295 doi:
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A centrifugal test was conducted on a reinforced embankment on soft clay using the interlayer of a three-dimensional geonet，which was made of high density polyethylene(HDPE) as model geogrid. In combination with the analysis of the photographs taken in flight，the development and distribution of tensions of the model grid were obtained. The strain gauges with epoxy resin were calibrated through continuous loading and multi-stage loading tensile test；and then elastic model and generalized Kelvin model were used to describe the characteristics，respectively. The experimental results show：(1) generalized Kelvin model is suitable to describe the mechanical properties of epoxy resin with the time factor；(2) as the stage of creep process has not been considered，the tension calculated by elastic model is approximately 16% greater than calculated by generalized Kelvin model，and the deviation is varied with the extension rate；and (3) the tension calculated based on the observed photographs is in agreement with that based on the measured strain. It is found that the accuracy depends on the displacement direction and magnitude.

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RESEARCH ON MICROSEISMIC ACTIVITY RULES IN DEEP HIGH-STRESS CONCENTRATION DISTRICT

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2008, 27 (11): -2302 doi:
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Based on monitoring the “time-space-intensity” of dynamic hazards，such as rockbursts，the research on activity rules of mining shock in deep coal mine is presented，especially in the area with high-stress concentration. By the microseismic(MS) monitoring system of Sanhejian Coal Mine，the activity rules of mining shock in the complete mining process of high rockburst liability working face 9202 are analyzed. The achieved results are as follows. (1) The strong correlation between the activity of mining shock and the district¢s maximum vertical stress gradient is revealed：the higher the maximum vertical stress gradient value is，the stronger mining shock signal is. The frequency spectrum would obviously move to a lower frequency band. (2) The different types of mining shock signals have the corresponding waveforms and frequency spectrum characters. Signal caused by relieve-shot presents the wide frequency spectrum，multi-peak high frequency characteristics，but rockburst omen signal shows a lower frequency and amplitude，and the main shock signal has a higher frequency and amplitude compared to omen signal. (3) To monitor and recognize rockburst danger district，the strong correlation among the intensity of mining shock signal，the amplitude of electromagnetic emission(EME) signal and drilling bits is observed. At last，the weakening and controlling technology of mining shock intensity was put forward on the basis of reducing the stress concentration factor，and in-situ practice，the anticipated effects are obtained.

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TREATMENT EFFECT ANALYSIS OF SHALLOW-BURIED CRUSHED SURROUNDING ROCKS UNDER UNSYMMETRICAL PRESSURE REINFORCED WITH SURFACE PREGROUTING TECHNOLOGY IN HIGHWAY TUNNEL

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2008, 27 (11): -2309 doi:
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Considering the case of shallow-buried crushed surrounding rocks under unsymmetrical pressure in a section of Guangfu tunnel to improve the strength of surrounding rocks and arching effect of tunnel，high pressure pre-grouting technology with cement grouting and cement-silicate grouting from ground surface is proposed to reduce the groundwater permeability of the surrounding rocks，and to protect water resources and ensure the safety of construction. The treatment effect is analyzed by numerical simulation and field experiment. The comprehensive analysis shows that after grouting，integral degree and strength of surrounding rocks are improved；and the velocity of convergence and crown settlement are increased. The deformation of tunneling is reduced；and the initial support and secondary lining mechanical behaviors are improved. The treatment of grouting is shown with good effect.

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CHARACTERISTICS OF MICROSEISM AT TYPICAL PERMAFROST SITES IN QINGHAI—TIBET PLATEAU

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2008, 27 (11): -2316 doi:
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Based on microseism tests at the typical permafrost sites along the Qinghai—Tibet Railway，the characteristics of frequency spectra of the permafrost sites are determined. The changes of the predominant frequencies with ground temperatures and permafrost tables，and the differences in frequency spectra between permafrost sites and loess sites are analyzed. Statistical curves of frequency spectra by Fourier analysis at these typical permafrost sites in the plateau are the shapes with single dominant peak value. The predominant frequencies of microseism¢s vertical components are between 3.3 Hz and 4.8 Hz；and the horizontal predominant frequencies are between 2.3 Hz and 4.7 Hz. The microseism is a macroreaction of lithologic characteristics，especially physico-mechanical features of those shallow strata，which depends on the strength of permafrost sites；and it will be changed with the ground temperatures and permafrost tables. Analytical results show that the predominant frequencies of microseism¢s vertical components are correlated with ground temperatures and permafrost tables at the permafrost sites：the higher the ground temperature is，the lower the vertical predominant frequency is；the higher the permafrost table is，the greater the vertical predominant frequency is. It indicates that there is a close relation between predominant frequencies and the strengths of permafrost sites. Moreover，a comparative result of microseism¢s predominant frequencies in permafrost sites and loess sites reveals that there is an obvious difference in predominant frequencies of microseism between the two different areas：the ranges of predominant frequencies at the permafrost sites are narrower than those of the loess sites；and there is a higher value of predominant frequency of microseism in the permafrost sites.

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MODEL TEST STUDY ON EFFECT OF GROUND FISSURE ON OPEN-CUT METRO TUNNEL WITH INTEGRAL LINING

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2008, 27 (11): -2324 doi:
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Based on the Xi¢an metro line No.2 passing through ground fissure active zones，the effect of ground fissure movement on open-cut metro tunnel with rectangular integral lining was studied by a large-scale structural model test with geometric proportion of 1∶5. The test results show that with settlement of the hanging wall of ground fissure increasing，the contact pressure of tunnel top increases in the hanging wall but decreases in the footwall；the contact pressure of tunnel bottom increases in the foot wall but reduces to zero in the hanging wall. When the settlement of hanging wall of ground fissure reaches 20 cm，the tunnel bottom in the hanging wall comes apart from soil，and tunnel lining within 2.5 m from ground fissure in the footwall firstly is found with cracks，so the foundation treatments such as grouting are needed in time. At the meantime，tunnel bottom is basically in compression；tunnel top is in tension in the footwall and initially in tension then in compression in the hanging wall. The deformation and failure model of tunnel induced by ground fissure is tensile failure，and tunnel cracks mainly appear in the footwall of ground fissure，but tunnel located in the hanging wall is basically good，which is just adverse to that the damage of buildings or structures on the ground surface caused by the ground fissure mainly in the hanging wall. The conclusions can be presented as the reference to structural design and prevention measures of metro tunnel passing through the ground fissure active zone.

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PROTECTION TECHNIQUES OF STEEP ROCK SLOPE WITH JYC ECOLOGICAL BASE MATERIALS IN HIGH-COLD AND
HIGH-ALTITUDE AREA

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2008, 27 (11): -2332 doi:
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[PDF 291 KB] (1430)

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According to the climate characteristics and the ecological environment in high-cold and high-altitude area of the West Sichuan Province in China，the local vegetation configuration pattern in the ecological slope protection has been proposed. Through a series of indoor and outdoor experiments，a new-type ecological base material of JYC is developed successfully. By indoor mixture ratio orthogonal test，the components of ecological material and its proportion have been studied，especially the coupling relation between its various characters and plant growth is analyzed. The in-situ experiment of ecological slope protection in more than three years has shown that the JYC has good performance of cohesion，and the ecological engineering structure composed of the base material, anchors，wire netting and plant roots makes the base material and the shallow layer of steep rock slope stable. Through the repeated rainfall erosion and the severe cold weather，it is proven that the JYC is able to bear and resist drought，freezing and corrosion. And the long-term spot sampling tests show that the new-type ecological base material of JYC contains rich nutrient content，the total nitrogen of JYC is more than 0.2%，effective phosphorus more than 20 mg/kg，effective potassium more than 200 mg/kg，and organism more than 5%，which can offer the nutrient for more than 10 years to the plant growth. The slope protection technology of ecological base material of JYC is more suitable for environmental protection and economical benefit than those of shotcrete-bolt support and grass planting by spraying concrete. The method of ecological base material slope protection embedded in macromolecule materials and magnetic manure is the development direction of slope vegetation protection technology for steep rock slope in the high cold and high altitude area.

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STABILITY EVALUATION AND TREATMENT SIMULATION OF AN EXPRESSWAY LANDSLIDE

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2008, 27 (11): -2340 doi:
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Based on the engineering geological exploration and site investigation of a landslide site induced by roadbed excavation on an expressway，the engineering geological conditions and the deformation characteristics of the landslide are described. It is concluded that the landslide is caused by excavation of the roadbed to decrease sliding resistance and to form a sliding air-face，resulting in the slope sliding along the weak interlayer between the overlying completely and intensely weathered siliceous sandy slate of the Jiangkou Group belonging to the Sinian System and the underlying intensely weathered siliceous sandstone of the Banxi Group. The numerical modeling results of stability indicate that the landslide is caused by low shear strength of the sliding plane and toe excavation，and that the resisting force should be applied to the toe of the slope by backfilling，and that stabilization measures should then be taken before continuing excavation of the roadbed. The shear strength reduction method is employed to compute the variations of the factors of safety with the depth of excavation before and after the slope is supported by anti-slide piles. It is indicated that the factor of safety of slope after stabilization is 1.33 when it is excavated to the designing roadbed；and it can meet the safe demand of the engineering.

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COMPARISON OF NUMERICAL SIMULATION WITH FINITE ELEMENT METHOD FOR VACUUM PRELOADING

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2008, 27 (11): -2347 doi:
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Based on the equivalent consolidation degree，the method that considers the smear effects diminishing the permeability of the clay in the smear zone，which can be transformed into the reduction on horizontal permeability coefficient of the soil in the efficient zone，is presented. The influence of consolidation degree induced by the size of element is discussed，in which the work-load of preprocessing can be saved and the smear effects are considered. The 3D finite element model is set up；and then the numerical simulation is executed combining with the project of vacuum preloading in Guangzhou Nansha Port. By comparing the results obtained by the usually used plane-strain method and the measured data，it is found that the results with the method proposed by J. C. Chai，which can transform the ground with sand-drains into homogeneous ground，are conservative，while the results with the method of the equivalent sand-walls are over-estimated；and it adjusts the permeability coefficients that are dependent on the intervals of sand-drains layout. The consolidation deformation with 3D FEM of ground installed by sand-drain presents more accurate than that of plane-strain method.

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DEVELOPMENT AND APPLICATION OF COAL AND GAS OUTBURST SIMULATION TEST DEVICE

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2008, 27 (11): -2354 doi:
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[PDF 437 KB] (1689)

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In order to understand the mechanism of coal and gas outburst，the large-scale test device for coal and gas outburst simulation is developed. The device is composed of outburst assembly，fast-releasing component，load-bearing frame，electric servo-controlled loading system，reversal unit，main frame bracket and accessories. The functions of this test device are analyzed as follows. (1) By using the electric servo-controlled loading system，uniform load and step load on the outburst coal sample can be realized；meanwhile，the outburst phenomenon caused by the concentrated stress in front of the coal face can be simulated. (2) This device can simulate five kinds of coal and gas outburst experiments on coal beds with different obliquities，which are under the different gas pressures and geostresses. (3) The foam-stainless steel is used to separate the coal sample from the air intake on the soleplate of the outburst assembly to realize the plane-charging for the outburst coal sample. (4) By using the fast-releasing component，the outburst ostium can be opened at once and its pressure will become zero. (5) The full process of coal and gas outburst can be monitored by this device. The experimental results indicate that the typical outburst hole appears，the powder coal shows the obvious separation；and the larger the outburst intensity is，the larger the gas pressure is. The experimental results agree well with the in-situ outburst characteristics and indicate that the large-scale coal and gas outburst simulation test device can simulate the outburst of coal and gas effectively.

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SERIALIZED DEVELOPMENT OF CSD–60 SLIDING MICROMETER

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2008, 27 (11): -2363 doi:
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[PDF 262 KB] (1324)

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CSD–60 sliding micrometer is developed in three stages，and precision sensor and INVAR steel are adopted in the device development. The CSD–60 sliding micrometer is developed from gauging distance and contraction style based on overseas products. Three invention patents are authorized；and the new products such as three-petal sliding micrometer are presented. Data acquisition instrument is considered corresponding to the products for improving the efficiency of in-situ tests；and related software is developed for data processing；so the firsthand monitoring information can be achieved. Long-term experiments on calibration and linearity assembly are performed for the serial products. Statistical analysis of the experimental data shows that observation theory and structure of instrument are greatly improved in the third stage；three-petal contact is prior to four-petal one in geometric stability. The precision of CSD–60 sliding micrometer is 0.02 mm/m with working temperature ranging from –10 ℃ to 50 ℃. Its water resistance is over 0.5 MPa，which can meet the requirements of civil engineering. If high accuracy sensor is applied to CSD–60 sliding micrometer or three-petal contact method is substituted for four-petal one，the gauging precision of CSD–60 sliding micrometer will be further improved.

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DISCUSSION ON THEORY AND PRACTICE OF ZONAL DISINTEGRATION IN SURROUNDING ROCKS OF DEEP ROADWAYS

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2008, 27 (11): -2369 doi:
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[PDF 432 KB] (1790)

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A discussion on zonal disintegration phenomenon and related theoretical problems in surrounding rocks of deep roadways were held in an academic salon about new ideas and new theories by Chinese Society for Rock Mechanics and Engineering. The contents of this academic salon cover the latest research achievements on zonal disintegration，e.g. measurement in-situ stresses and experimental research result analyses of a laboratory，explanation and different phenomena and their formation mechanisms about zonal disintegration，and the development of numerical analysis methods. Moreover，some hot issues such as the meaning and research methods about zonal disintegration are also discussed. Although the study of zonal disintegration is in a groping state and some controversies on present research results still exist，the discussions are very helpful for scientific achievement in this research subject and have an enlightening influence on acknowledgement and disposal methods of this research work on zonal disintegration.

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STUDY ON INTELLIGENT BACK ANALYSIS METHOD FOR LONG-TERM STABILITY OF ROCK ENGINEERING AND ITS APPLICATIONS

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2008, 27 (11): -2376 doi:
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[PDF 98 KB] (1379)

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四位华人青年学者荣获国际岩土力学计算方法与进展协会(IACMAG)大奖

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2008, 27 (11): -2377 doi:
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[PDF 154 KB] (1768)