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2009, 28 (09): 0-0 doi:

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STUDY AND APPLICATION OF INVERSE CONTROLLING TECHNOLOGY FOR 3D GEOMECHANICAL MODEL CONSTRUCTION OF UNDERGROUND ENGINEERING

LI Zhongkui，WANG Aimin，WANG Kezhong，LIAO Yi，FU Shengyao

2009, 28 (09): 1729-1734 doi:

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As an important research method，geomechanical model test is used to analyze the deformation and stability state of rock engineering and underground engineering. Construction technologies of the model often determine the feasibility of the model test and the credibility of the result to large extent. The controlling technology for 3D geomechanical model has been researched，through introducing two three-dimensional geomechanical model tests；how the bulk density grows as the depth increases in the inner model was studied by taking samples on in-situ tests with different depths，which were constructed and controlled by the fixed volumes of the materials of the models. A design and construction method is suggested；the bulk density of model material reduces as the depth increases by the so called inverse controlling method，which was carried out in another three-dimensional model test of the subway station extended from shield tunnel. The results of sampling taken from in-situ of the model test show that constructing model by this design method is available；and the density and property of the model material are uniform and stable.

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RESEARCH ON LARGE-SCALE TRIAXIAL COMPRESSIVE RHEOLOGICAL TEST OF SOFT ROCK IN DEPTH AND ITS
CONSTITUTIVE MODEL

CHEN Weizhong1，TAN Xianjun1，LU Senpeng1，YANG Jianping1，WU Guojun1，YU Hongdan1，
WANG Zhengming2，ZHU Lin2

2009, 28 (09): 1735-1744 doi:

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The in-situ rheological test under three-dimensional stress is a very useful way to reflect the actual rheological properties of filed rock mass. The test process，method and results of in-situ large-scale true triaxial test are presented. Variation law of deformation with time is further analyzed；and the experimental curve is described using a nonlinear kinetic creep model. Then，the theoretical rheological equation is established；each parameter of creep model is obtained and the rheological characteristics of deep soft rock are well reflected. The results show that the creep rate of mudstone is not only related to stress state，but also to time. The results can be applied to the estimation of long-term deformation of engineering tunnel in soft rock engineering and design of support，which have important reference values to the optimization design of tunnel support of soft rock.

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STUDY ON SOME ENGINEERING GEOLOGICAL PROBLEMS OF WEST ROUTE OF SOUTH-TO-NORTH WATER TRANSFER PROJECT

WANG Xuechao

2009, 28 (09): 1745-1756 doi:

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The assess principle and basic idea of regional tectonic stability are discussed based on engineering practice. The zoning of regional tectonic stability is obtained according to geological data in region of first stage West Route of South-to-North Water Transfer Project. Faults nearby the project are nonactive. There are no active faults and seismic epicenters in dam sites and tunnel areas. The crust of the project site is relative stable. The surrounding rock masses are mainly grades II-III，and rock classifications of grades IV-V are distributed regionally. Density of rockburst is not high. Deformational phenomena of surround rocks exist in slate strata and faulted zones. In case of surrounding rock and deformation feature，the tunnel boring machine(TBM) is applicable to the project. The possible water quantities flowing into tunnel are calculated initially. There are possible zones of groundwater inflowing in the section of shallow tunnel，syncline core and faulted zones.

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STUDY OF 3D GEOMECHANICAL MODEL TEST OF ZONAL DISINTEGRATION OF SURROUNDING ROCK OF DEEP TUNNEL

ZHANG Qiangyong，CHEN Xuguang，LIN Bo，LIU Dejun，ZHANG Ning

2009, 28 (09): 1757-1766 doi:

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In order to simulate the generating condition and reveal the failure mechanism of zonal disintegration， the formation process of zonal disintegration through 3D geomechanical model test of the Dingji coal mine deep tunnel in Huainan mine is reconstructed area and the changing laws of strain and displacements of the surrounding rocks by means of various advanced and exact measurement methods are obtained. The formation conditions and failure laws of zonal disintegration of deep tunnel have been revealed through model test，which lays a solid test foundation for further studying nonlinear deformation and failure mechanism of deep tunnel.

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GUIDED WAVE DETERMINATION METHOD OF SERVICE LOAD IN PARTIALLY GROUTED BOLT

HE Wen，WANG Cheng，NING Jianguo，TANG Yonggang

2009, 28 (09): 1767-1772 doi:

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Longitudinal guided wave is used to inspect the service load in the partially grouted bolt nondestructively. The stress distribution characteristics of free section and anchoring section in the partially grouted bolt under service load was first analyzed and tensile stress keeps constant in the free section of the bolt. Then group velocity of longitudinal guided wave propagating in the free section of the bolt under different tensile stresses was calculated. The results show that the group velocity decreases linearly with the increase of tensile stress within the elastic distortion range. Experiments were conducted to study the reflection of longitudinal guided wave from the upper interface of anchoring section of partially grouted bolt；and it shows that the upper interface reflection wave can be observed clearly when the frequencies of guided wave are 45–75 kHz. The reflection of longitudinal guided wave from the upper interface of partially grouted bolt and the time of guided wave propagating in the free section of the bolt can be used to determine the service load in the partially grouted bolt；and the theoretical and experimental results of service load-propagation time have the same trend.

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IN-SITU TEST ON SURROUNDING ROCK DEFORMATION IN SUPER- LARGE SECTION AND LARGE-SPAN TUNNEL

ZHOU Dingheng1，QU Haifeng2，CAI Yongchang1，CAO Liqiao3，YANG Hongwei4

2009, 28 (09): 1773-1782 doi:

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According to construction of Longtoushan two bores and eight lanes tunnel with super-large section and span in Guangzhou，the monitoring of surrounding rock deformation was carried out. Based on the measured data，the law of the deformation varying with time and the longitudinal and radial incidences of different construction procedures were analyzed. It is shown that the surrounding rock deformation can be better controlled using the two-side pilot drifting method. During the construction of super-large section and span tunnel，the excavation of the upper bench in the right drift，the down bench in the left drift and core rock have great influence on surrounding rock deformation，which are the main stages to control the surrounding rock deformation. The longitudinal incidence of the excavation of the super-large section and span tunnel is about one time of the drift diameter，about 6 to 8 m. And the radial incidence in the vertical direction of the ceiling is about 25 m and radial incidence in the 30° direction of the ceiling in the left drift is about 15 m. The experience and conclusions presented can be used as reference in the design，construction and site monitoring of similar tunnels.

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STUDY OF DISPLACEMENT PREDICTION MODEL OF LANDSLIDE BASED ON RESPONSE ANALYSIS OF INDUCING FACTORS

DU Juan，YIN Kunlong，CHAI Bo

2009, 28 (09): 1783-1789 doi:

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The change of landslide displacement is determined by dynamic functioning of inducing factors besides the basic geological conditions. In order to establish the response relation between dynamic changes of landslide displacement and inducing factors，time series decomposable model is used to decompose the displacement into trend term and periodic term by moving average method. Trend term displacement is determined by the potential energy and constraint condition of the slope and is predicted by displacement polynomial function. Periodic term displacement is affected by the periodic dynamic functioning of inducing factors，such as rainfall，reservoir level fluctuation and so on. The rainfall of current month，cumulative rainfall of anterior two months，reservoir level fluctuation of current month and cumulative increment of total displacement in current year are selected as influencing factors，and the multivariable BP neural network is adopted to predict the displacement. The prediction values of trend displacement and periodic displacement are superposed to obtain total displacement prediction. This model is used to deal with the data of displacement，rainfall and reservoir level fluctuation of Baishuihe landslide in the Three Gorges reservoir area. The results indicate that the prediction model based on the inducing factors and the landslide displacement comprehensively can reflect the key role of dynamic change of inducing factors in displacement development and can improve the precision and effectiveness of prediction results.

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ANALYSIS OF CONSTRUCTION MONITORING OF LARGE-SECTION BOX CULVERT JACKING PROCESS UNDERPASS EXPRESSWAY

QIN Weimin1，CHU Bin2，LONG Lizhi3

2009, 28 (09): 1790-1797 doi:

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There is a large-section box culvert jacking underpass expressway in Zhengzhou—Kaifeng city access project with the largest section size in China. Systematic monitoring work is arranged for the project，the deformation on expressway and the box posture control are focused on the whole jacking process. Monitoring results show that over half of total settlements appear after the first box section underpass on west side expressway；the southern region is over 60% and the northern region is over 54%；while the box culvert is jacked into the 3/4 width of the expressway，the deformation on expressway begins to speed up on both ends. Analysis shows that engineering characteristics such as thin coverage，large-section and unfavourable geological conditions are the main factors leading to large deformation on expressway；the fact that design idea has not been carried out in jacking process increases the deformation on expressway，which leads to poor quality in construction of pipe shed and pilot draft. By analysing the monitoring information of the box and the surrounding environment，some reference can be achieved in similar projects in the future.

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MODEL TEST STUDY OF SLOPE INSTABILITY INDUCED BY
RAPID DRAWDOWN OF WATER LEVEL

JIA Guanwei，ZHAN Liangtong，CHEN Yunmin

2009, 28 (09): 1798-1803 doi:

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There are many slopes adjacent to water in nature，such as river banks，coastal dykes，earth dams，and reservoir and lake banks. Rapid drawdown of water levels often induces landslides of this kinds of slopes. A large-scale model test was performed to investigate the failure mode and causes of landsides of the slope adjacent to water during rapid drawdown of water level. The model slope is 15 m long，6 m high and 5 m wide，and the height of sloping part is 4 m. A water-level control system was developed to implement the simulation of the rapid drawdown of water level. Pore water pressures，total earth pressures，the slip surfaces and formation and development process of cracks on the slope were recorded during the simulation process by digital camera，high precision sensors，side tracers，etc.. The model test results indicate that the pore water pressure inside the slope showed a significant delay related to the drawdown of water level outside the slope. It indicates that measures that can lower the water levels inside the slope should be helpful to stabilize the slope. The failure mode that developed during rapid drawdown of water level was of the multiple retrogressive type. The experimental results can provide an improved understanding of the physical behavior and failure mode of soil slopes subjected to rapid drawdown of water level.

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AMELIORATION AND APPLICATION OF COAL AND GAS OUTBURST SIMULATION EXPERIMENT DEVICE

XU Jiang1，TAO Yunqi1，2，YIN Guangzhi1，LI Shuchun1，CHENG Mingjun1，PENG Shoujian1

2009, 28 (09): 1804-1809 doi:

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In order to ensure the better effect of coal and gas outburst simulation experiment，aiming at shortages of originally developed simulation test platform，the outburst mould and its additional coal forming device have been improved and developed. Using the technologies of ring direction and surface sealing，etc.，omnidirectional sealing，good sealing result for a long time under 2 MPa gas pressure is obtained. With three groups of different circular outburst port diameters，different outburst port experiments of coal and gas outburst simulation under non-replace outburst mould can be conducted，which is economical and practical. Depending on connection between existing temperature，pressure sensors and its additional test control software，real-time monitoring of change law of coal temperature and gas pressure in the process of outburst can be realized conveniently. The separated coal sample molding equipment can add the preconcerted compacting pressure accurately；and it is well established for its flexible operations. The simulation tests carried out by the improved coal and gas outburst simulation test device indicate that there are threshold values of gas pressure and outburst aperture which affect coal and gas outburst occurring or not. When they are greater than the threshold values，the outburst intensity will increase with the increase of the gas pressure or outburst aperture. As the power of outburst，the gas pressure has a certain porphyrization effect on the outburst coal powders. In addition，the temperature change of coal body during coal and gas outburst process has also verified that it is thermopositive when coal absorbs gas，while it is decalescent with releasing gas.

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HIGH RESOLUTION REMOTE SENSING SURVEY AND MECHANISM ANALYSIS FOR YANMEN VILLAGE LANDSLIDE

WANG Zhihua，XU Qide，XU Bin

2009, 28 (09): 1810-1818 doi:

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A landslide occurred on July 7th 2007 in Yanmen village of Daxian County，Sichuan Province，and it caused economic loss of about RMB 0.15 billion. The information of the geological environment of the Yanmen slope，the displacement of roads，pools and tree groups，and the elevation variety before and after the landslide occurrence had been captured using high resolution satellite image with digital landslide technique. Based on the deformation characteristics the slope is divided into 4 regions：main sliding region，retrogressive sliding region，intensive influence region and influence region；and their moving styles are considered as quick push+sand soil liquefaction and flow in plane manner at the front part，retrogressive sliding，tension cracks，deformation and partial displacement caused by tension force，small cracks and deformation caused by land shake. With DEM，the volume of mass of sliding out and deposit from ground before landslide were estimated as 132.6×104 and 132.2×104 m3 respectively；and combining with drilling data，the landslide volume from sliding surface is estimated as 1.97×106 m3. The lithology and geological structure conditions for Yanmen village slope are feasible for forming a landslide but it is difficult to form large-scale and thick ones since it faces a small and narrow valley which is suitable for developing partial and shallow landslides. Long-term and intensive rainfall was the main inducing factor for forming Yanmen village landslide. As for whole slope，the movement of landslide occurred on July 7th，2007 had not release energy sufficiently，therefore，in conditions of continuous rainfall，landslides may occur in parts of the slope but it is hard to have the large-scale landslide of whole slope.

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SAFETY MONITORING AND STABILITY ANALYSIS OF LARGE-SCALE AND COMPLICATED HIGH ROCK SLOPE

ZHANG Jinlong1，2，XU Weiya1，2，JIN Haiyuan1，2，LIU Dawen3，CAI Dewen3

2009, 28 (09): 1819-1827 doi:

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The stability of high rock slope is one of important issues during construction period of a hydropower station，which is related to success of project. The stability of the left bank excavation slope of Jinping first stage hydropower station is remarkable because of its high ground stress，faults and fissures developed，large-scale excavation，deep unloading and complicated geological conditions. The layout of safety monitoring of the left bank excavation slope is introduced；the deformation trend，spatial distribution and the relationship between deformation and excavation of surface deformation points are investigated. The deformation size and the relationship between deformation and structural face of multi-point extensometers are discussed. The deformation laws of rock mass of the left bank slope are obtained based on the comprehensive analysis of the monitoring results of surface deformation points，multi-point extensometers，graphite bar-type extensometers，measurement of valley width，anchor cable dynamometers and shearing-resistance tunnels. The research result shows that the influence scope of excavation in left bank slope is larger than 80 m；and the magnitude of relaxation deformation of the left bank slope is relatively large. The process of transfer and release of slope rock mass is long and the longer time is needed for the slope to reach complete stability. The monitoring results can be used for reference by other similar engineering.

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STUDY OF METHOD FOR SIMULTANEOUSLY MEASURING ADSORPTION-DEFORMATION-PERMEABILITY OF COAL

FANG Zhiming1，LI Xiaochun1，BAI Bing2

2009, 28 (09): 1828-1833 doi:

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In recent years，with the increasing concern of CO2 sequestration in coalbed and enhanced coalbed methane production by gas injection technologies，lots of scholars start the research on measuring adsorption，sorption-induced deformation and permeability of coal；and a large number of test devices and technologies have been developed. However，it is difficult to measure adsorption，sorption-induced deformation and permeability on one test specimen at the same time，and there is no similar report on related method and test device. A method for simultaneously measuring adsorption，sorption-induced deformation and permeability，which uses the cylindrical block as test specimen，and deformation sensor for sorption-induced deformation measurement and dual-syringe pump for adsorption and permeability measurement，has been proposed. The principle，test device and procedure of the method have been described first，and then，a test has been carried out for simultaneously measuring adsorption，sorption-induced deformation and permeability of coal by use of CO2. The results indicate that the proposed method and test device are suitable for simultaneously measuring adsorption，sorption-induced deformation and permeability of coal，and the results are satisfying.

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EXPLORATION OF TWO-GATEWAY NETWORK PARALLEL ELECTRICAL TECHNOLOGY FOR EXPLORING THIN-COAL AREA WITHIN COAL FACE

WU Rongxin1，ZHANG Pingsong1，LIU Shengdong2

2009, 28 (09): 1834-1838 doi:

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The two-gateway network parallel electrical technology is first prevented to explore the thin-coal area within coal face，which is a new geophysical surveying means for the geological anomaly bodies especially within the large width of coal faces that are difficult to be detected by the conventional radio-wave penetration method. With more simple data-collecting modes，the network parallel electrical method realizes the synchronous potential measurement of whole electrode array；so the data-collecting efficiency is greatly improved and the signal-to-noise ratio is also well enhanced. The collected data can be used for resistivity inversion of different electrode devices. The two-gateway two-dimensional resistivity tomography makes full use of the data collected by the network parallel electrical instrument from the several survey lines of both gateways with the electrodes set in the coal wall along the central lines；then，the resistivity variations between the two gateways are acquired. Based on the electrical property differences between thin-coal area and normal coal seam，the capable resistivity images of thin-coal area are analyzed. In addition to the known geologic data，property and distribution ranges of thin-coal area can be analyzed. The exploration case for thin-coal area from the mechanized coal face in Zhangji coal mine of Huainan Coal Mining Group Corporation shows that，the method can explore the areal extent of thin-coal area within coal face，which gives a good guidance to coal production.

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A REVIEW OF STEADY STATE SEEPAGE IN A SINGLE
FRACTURE OF ROCK

XIONG Xiangbin，ZHANG Chuhan，WANG Enzhi

2009, 28 (09): 1839-1847 doi:

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Three aspects of seepage research in a single fracture are involved as follows：(1) the behavior of fluid flow in a single fracture，which studies the fluid flow models and flow velocity distribution in a single fracture；(2) the main factors controlling fluid flow in a single fracture，including stress，aperture，roughness，filling material，multi-field coupling and so on；(3) the methods of single fracture flow numerical simulation，including techniques of generating numerical fracture and numerical simulation methods. These current achievements are reviewed systematically. Based on discussion of the encountered problems，several results are summarized. The law of fluid flow in a single fracture is very complex. There are still many ambiguities in the research of seepage model and mechanism. It is recommended to introduce precision instrument to meet the requirement of experience. Shear stress influence on seepage is another hot issue. 3D stress and tensile influence on seepage stress are also the future research direction. But the lack of equipment，which could be used to simulate the complex stress state，is the “bottleneck”；the evaluation of the fracture roughness is complicate. Since numerical simulation and experience complement each other，it is very important to choose a reasonable numerical simulation method.

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METHODOLOGY FOR MODELING OF COMPLEX GEOLOGICAL FAULTS IN GEOTECHNICAL ENGINEERING BASED ON ELEMENT RECONSTRUCTION

ZHANG Yuting，XIAO Ming，ZUO Shuangying

2009, 28 (09): 1848-1855 doi:

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The modeling of geological faults is a difficult issue in the numerical analysis of geotechnical engineering. The methodology for modeling of complex geological faults is proposed by using element reconstruction. This method firstly discretizes the analysis objects without taking geological faults into consideration. Then，by conducting element reconstruction，the geological faults can be constructed into the model. The element reconstruction is to establish fault-free models by using eight-node hexahedron element at first. Afterwards，by using four-node tetrahedron，five-node rectangular pyramid and six-node triangular prism，the meshes that are intersected by structural planes can be reconstructed and the fault-contained model is obtained. And the fault-contained model has multi-form elements. Then，the proposed method is illustrated with its applications to several geotechnical examples，including the modeling of geological faults in complex underground bifurcation pipe，abutment and foundation of gravity dam and large-scale underground caverns. These applications prove the effectiveness of proposed method. The numerical analysis is further conducted by taking underground caverns as an example. By using common software，the excavation simulation is performed on the fault-free model and fault-contained model of underground caverns，respectively. The elements of geological faults in fault-contained model are directly simulated by entity elements. By comparing the results of different models，it is discovered that the distributions of surrounding rock deformation and stress show a remarkable discontinuous feature in the fault-contained model. The surrounding rock intersected by geological faults observes an increase of displacement and a release of stress. This indicates that the meshes generated by the proposed modeling method can be used in numerical analysis and influences of geological faults on surrounding rock stability can be properly reflected as well. Thus，the reliability of proposed method is demonstrated，providing the modeling of complex geological faults in geotechnical engineering with a convenient way.

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INTERACTION ANALYSIS OF DOUBLE HOLES EXTREMELY CLOSE APPROACHING PARALLEL SHIELD TUNNELS CONSTRUCTION

TAO Lianjin1，SUN Bin2，LI Xiaolin2

2009, 28 (09): 1856-1862 doi:

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The case study presented is based on a new shield tunnel approaching，which is close to an existing subway tunnel in Beijing. With theoretical analysis，numerical modeling and the feedback of field monitoring，the influences on the existing shield tunnel in terms of longitudinal and transverse displacements，bending moment，and axial force brought by the newly parallel approaching one are investigated. And it reveals that there is the longitudinal effect on the existing tunnel when the extremely close shield moves forward，which is presented as the phenomenon of “early stress arrival and deformation lagging”. The study results verify that the effectiveness of the cross steel support is remarkable and especially the transverse steel support makes a great contribution to the improvement the existing tunnel stress state，which may provide informative experience for relevant cases.

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NEW METHOD OF CALCULATION OF PROJECTILE PENETRATION INTO ROCK

WANG Mingyang1，TAN Keke2，WU Huajie1，3，QIAN Qihu1

2009, 28 (09): 1863-1869 doi:

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According to the theory of short wave and internal friction model，the resistance of projectile is obtained from relationship of momentum conservation on the wavefront and continuum condition of the surface of projectile. The ratio scale relationship of penetration and perforation is revealed by the relationship energy transfer in the process of fragmentation zone to radial crack zone. A new generalized formula for calculating the penetration depth of non-deformable projectile is obtained from the projectile. The comparison between experiential formula results and the theoretical results verifies the validity of theory.

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DYNAMIC DETECTION OF OVERBURDEN DEFORMATION AND FAILURE IN MINING WORKFACE BY 3D RESISTIVITY METHOD

ZHANG Pingsong1，2，LIU Shengdong2，WU Rongxin1，CAO Yu3

2009, 28 (09): 1870-1875 doi:

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The three-dimensional DC method and technology for detecting overburden failure are introduced. Through several bores drilled in the top and floor rock of the coal seam in laneway，the detecting section between two bores is formed. Then through 64 poles fixed in different location of bores，the characteristics of the electric field in the top rock of different periods can be surveyed according to the mining plan. Through 3D inversion，the rock¢s resistivity of detecting area can be gained. So the changing characteristics of overburden distortion and failure from overtaking stress of mining to stable failure of anaphase can be analyzed and researched comprehensively. It provides effective technical parameters for safety production of mine. During the detecting application to overburden failure by 3D electrical method between two bores in Huainan Mine，28 groups of data are obtained continuously. The dynamic developing characteristics of overtaking stress and rock¢s distortion and destruction because of mining are analyzed and given. The height results of caving zone and fractured zone are inosculate with the calculating value according to the mining regulations under water，railway and building. The results of application show that the detecting technology by 3D electrical method between two bores has several merits，such as low cost，accurate results and dynamic detecting characteristics，and so on，compared with the traditional drilling method from ground and other detecting methods in mine. The independent and innovative technology has remarkable application and extending values in similar mines.

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EXPERIMENTAL STUDIES OF SUBSIDENCE AND EXPANDABILITY OF MONTMORILLONITIC SOFT ROCK PARTICLES UNDER ELECTROCHEMICAL TREATMENT

WANG Dong1，KANG Tianhe1，CHAI Zhaoyun1，HAN Wenmei1，2，LIU Zhiping3

2009, 28 (09): 1876-1883 doi:

[PDF] 240 KB (1286)

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An experimental apparatus affecting the expandability of montmorillonitic soft rock particles under electrochemical treatment has been developed；experimental study of the subsidence and expandability of soft rock particles affected by distilled water，NaCl solutions，NaCl electrolyte concentrations and electric gradients is carried out. The experimental results are as follows：the treatment of direct current can change subsidence rate of soft rock particles in distilled water but its volume expandability is not affected when the subsidence is in stable state. With increasing in NaCl electrolyte concentrations，the subsidence rate of soft rock particles increased and then the swelling ratio declined of negative index while the subsidence was finished. On the basis of the stabilization and then addition of the electric gradient of 0.5 V/cm，sample volumes decrease，and the swelling ratio of soft rock particles has the same variation with above mentioned. It seems that the electric gradient of 0.5 V/cm can provide sufficient electromotive force for the subsidence and the expandability of soft rock particles. Increment of electric again gradient can not affect the volume expandability of samples in stable state after the electric gradient of 0.5 V/cm applied. With the increment of electrolyte concentrations，both electrical currents of soft rock particles and temperatures of the experimental system increased with the treatment time，both electrical currents and temperatures reduced because electrolyte concentrations weakened. During the electrochemical treatment，electrode reactions and electrolysis have been observed. It caused the variance of pH values of soft rock particles. pH value decreases in the anodic region which is acid while pH value increase in the cathodic region which is alkaline.

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EXPERIMENTAL STUDY OF EARTH PRESSURE FOR ANISOTROPIC SAND CONSIDERING LATERAL DISPLACEMENT

SONG Fei1，2，ZHANG Jianmin1，2

2009, 28 (09): 1884-1895 doi:

[PDF] 450 KB (1318)

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Strong dependence of earth pressure coefficient on lateral strain constraint is investigated by strain path tests of anisotropic sand under different constant strain increment ratios. In addition，centrifuge model tests for earth pressure are conducted to vertify the rules of material test. On the basis of centrifuge model test results，variation of earth pressure and displacement field of the backfill with wall movement is compared and analyzed for anisotropic soil with different particle orientations. It is shown that for the two cases in which the maximum principal stress acts perpendicular to and parallel with the bedding plane，the difference of the sliding mass and the earth pressure is small when the backfill is near the K0 state. While it becomes larger with the increase of wall movement. The sliding mass and the earth pressure are relatively smaller when the maximum principal stress is perpendicular to the bedding plane. In comparison with the isotropic case，anisotropy can increase the earth pressure at rest；but it has little effect on the earth pressure at the limit state，indicating that the effect of compression anisotropy is obviously stronger than that of strength anisotropy.

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TEMPERATURE AND DEFORMATION DIFFERENCES BETWEEN SOUTHERN AND NORTHERN SLOPES OF HIGHWAY EMBANKMENT ON PERMAFROST

CHOU Yaling1，SHENG Yu2，WEI Zhenming3

2009, 28 (09): 1896-1903 doi:

[PDF] 293 KB (1492)

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Based on the observation data of the embankment in test section K369，the characteristics of the ground temperature and the deformation of the embankment are analyzed；and the relationship between the ground temperature and the deformation is presented. The observation data indicate：(1) the embankment transverse deformation difference has close relationships with the ground temperature transverse difference of the embankment，and it is controlled by the ground temperature state and its variation；(2) the difference of solar radiant amount on slopes results in transverse thermal difference in the embankment，and also leads to the transverse uneven settlement difference；and (3) the development of embankment deformation lags behind the development of embankment temperature，so the time of the largest settlement deformation is not equal to that of the maximum thaw depth. For the embankment with uneven deformation，the times of the largest settlement deformation on two sides of embankment are different；and the time of the largest settlement deformation on the south side is later than that on the north side of the embankment. The deformation difference will be aggravated with time；and finally the embankment stability is affected by longitudinal cracks of embankment caused by asymmetric settlement of permafrost.

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DYNAMIC STABILITY PSEUDO-STATIC ANALYSIS OF
REINFORCEMENT SOIL SLOPES

ZHAO Lianheng，LI Liang，YANG Feng，DAN Hancheng，LIU Xiang

2009, 28 (09): 1904-1917 doi:

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The reinforced soil structures are employed widely due to the technical and economical advantages in static state. In addition，the use of reinforced soil structures in seismic areas has been increased due to their excellent seismic stability，but the vertical seismic effects on the stability of reinforced soil structures are seldom considered. The effects of horizontal and vertical pseudo-static forces on reinforcement soil slopes are investigated by applying the kinematical approach of limit analysis theory. In particular，the effects of the distribution mode of the reinforcement force on the seismic stability of reinforced soil slopes have been investigated as well. Both rotational failure surface and planar slip surface are considered and each analytical expressions is derived to calculate the reinforcement force，which are required to prevent failure and the critical height of reinforced slopes subjected to earthquake loading. The upper bound solutions for each analytical expression are presented by applying a nonlinear sequential quadratic programming algorithm. From the contrastive analysis，it is shown that the solutions presented here agree well with available predictions both in simple static state and dynamic state. All of the seismic force，the material characteristic of soil and the gradient of slope have significant effects on the seismic stability of reinforcement slope. The effect of vertical seismic acceleration on the stability of reinforcement slopes is significant，especially for steep slope，poor quality filler and high value of horizontal seismic acceleration，which means that ignoring the effect of the vertical seismic acceleration could result in an unsafe design. Besides，some suggestions for engineering practice are proposed.

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AN ELASTOPLASTIC CONSTITUTIVE MODEL OF SANDS CONSIDERING CYCLIC ROTATION OF PRINCIPAL STRESS AXES

TONG Zhaoxia1，2，ZHANG Jianmin2，ZHANG Ga2

2009, 28 (09): 1918-1927 doi:

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The deformation behavior of sands under cyclic rotation of principal stress axes can be concluded as follows based on the current test results. Firstly，the volumetric strain induced is increased with the increase of cycles number，yet its increase rate is lowered with its progressive accumulation. Secondly，the hysteretic loop is produced for the shear stress and strain components. And the unclosed hysteretic loop tends to be closed with the increase of rotation cycle numbers. Thirdly，the obvious non-coaxiality between directions of the plastic strain increment and stress shows segment characteristics. Finally，the effects of the intermediate principal stress parameter are significant. The accumulation rate of the volumetric strain is increased with the increase of the intermediate principal stress parameter under otherwise identical conditions. Based on the above physical fundamentals of sands subjected to cyclic rotation of principal stress axes，a new cyclic elastoplastic constitutive model for saturated sands aiming at describing the deformation behavior of sands due to cyclic rotation of principal stress axes is developed. And its effectiveness under the complex stress paths including cyclic rotation of principal stress axes is verified by comparison of simulation model and test results；and it is shown that the proposed constitutive model is capable of predicting reasonably the developments of strain components and the volumetric strain in various conditions including principal stress axes rotation.

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CONSISTENT MODEL OF TRANSLATIONAL FAILURE ANALYSIS
OF SANITARY LANDFILLS WITH REFUSE DAM

TU Fan，WU Xiaojie，WANG Quanfeng

2009, 28 (09): 1928-1935 doi:

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Consistent model to analyze the translational failure of sanitary landfills with refuse dam along the lateral phase and the base of landfill as well as the back or base of refuse dam is developed. The failure body is divided into active，middle and passive wedges. An equation is established to calculate the safety factors through limit equilibrium analysis of every wedge. According to the maximum relative differences between average and true safety factors；and the relationship between the safety factors of wedges and whole fills are analyzed. The safety factors are also compared with the results of the model of two wedges for landfills without refuse dam and the model of one failure style only for landfills with refuse dam. It is shown that the consistent model is corrective，suitable and comprehensive. The model can consider the influence of the section of refuse dam，the force direction between the back of wall and the waste fill as well as the cohesion along the interfaces of combined liner system，which overcomes the limited conditions of some models. The model can also be used to analyze the translational failure of landfills without refuse dam. The optimum design of refuse dam can be conducted according to the results of the consistent model.

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MESO-MODEL TESTING AND NUMERICAL SIMULATION OF NAIL-SOIL CONTACTS DURING PULL-OUT

ZHOU Jian1，2，GUO Jianjun1，2，CUI Jihong3，JIA Mincai1，2

2009, 28 (09): 1936-1944 doi:

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Using technique of image visual tracing and non-target measuring，the meso-model tests of the rough nail-soil during pull-out in dense sand were carried out. The displacement field of the nail-soil contacts，trajectories of the sand particles，and shear strain of sand particles of contacts were analyzed during the process of pull-out of nail-soil. The result shows that in the first instance，the displacement motion of the particles is vertical and then was horizontal；also the particles have shear expansion action. The soil shear strain around the nail-soil changes in radial and regional role from top to bottom of the nail is symmetry. Based on the model test，the particle flow code in 3D(PFC3D) method was introduced to simulate the pull-out process of nail-soil，Firstly，the law of displacement field of contacts between soil and nail in model test was verified in meso-scale. Then，the PFC3D method is used to discover some changes regular of meso-mechanism，such as the porosity and coordination numbers during the process of the pull-out of nail-soil. It is revealed that the porosity of the sand around nail-soil reduced with the increase of the distance to the nail-soil；and the porosity contour of the sand in the end of nail-soil was gradually outward proliferation，which was irregular concentric circles；coordination numbers were the smallest around the nail and soil contacts，and gradually increasing to the outside. The study is expected to contribute to disclose the mechanism of soil nail pull-out and the development of contacts.

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2009, 28 (09): 1945-1945 doi:

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2009, 28 (09): 1946-1946 doi:

[PDF] 107 KB (1260)

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