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Ge X.R.,Shanghai JiaoTong University | Ge X.R.,CAS Wuhan Institute of Rock and Soil Mechanics | Ge X.R.,State Key Laboratory of Geomechanics and Geotechnical Engineering | Hou M.X.,Shanghai JiaoTong University
Science China Technological Sciences | Year: 2012

As a main constituent of geological body, the rock masses have distinct differences from other materials, one of which is that rock masses are initially stressed in their natural states. Hence, it is an extremely challenging and significant research project to know the present residual stress of the rock masses in the earth's crust. Although some regularities of distribution of in-situ rock stresses can be deduced, the basic means to study the state of rock stress is in-situ stress measurement. After a brief review of several measuring methods of in-situ 3D rock stress, a new one, borehole wall stress relief method (BWSRM) to determine the in-situ 3D rock stress tensor in a single drilled borehole was proposed. Based on the principle of in-situ rock stress measurement with BWSRM, an original geostress measuring instrument was designed and manufactured. Preliminary experiments for determination of in-situ stress orientation and magnitude were carried out at an experimental tunnel in Jinping II hydropower station in China, where the buried depth of overburden was about 2430 m. The results showed that it was feasible to measure the in-situ 3D rock stresses with BWSRM presented in this paper. The BWSRM has a broad prospect for in-situ 3D rock stress measurements in practical rock engineering. © Science China Press and Springer-Verlag Berlin Heidelberg 2012.

Ge X.R.,CAS Wuhan Institute of Rock and Soil Mechanics | Ge X.R.,State Key Laboratory of Geomechanics and Geotechnical Engineering | Ge X.R.,Shanghai JiaoTong University
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

A new approach, named the Vector Sum Method (VSM), is proposed to analyze the anti-sliding stability problems for slope, dam foundation, etc. It is well known that the strength reduction method is generally applied in this field. But the stress state due to the strength reduction is a virtual state rather than a real one. So the safety factor calculated based on a virtual stress state is not physical sound. Some disadvantages of slope and dam foundation stability analysis methods based on strength reduction principle are discussed. To overcome the limitation of the strength reduction method, the VSM uses the real strength parameters rather than the reduced parameters to compute the stress field. The safety factor is computed based on the real stress state and the vector sum algorithm. Several typical examinations calculated by the vector sum method are presented. The comparison between results shows that the VSM is reasonable. The safety factor is calculated by an explicit formula in 2D case while by iterative computation in 3D case after the stress fields are acquired by finite element method or other methods. The VSM can be well applied to 3D problems for its simplicity and efficiency. © 2012 Taylor & Francis Group, London.

Sun J.-Z.,Wuhan University of Technology | Sun J.-Z.,State Key Laboratory of Geomechanics and Geotechnical Engineering | Xiao W.-H.,Wuhan University of Technology
Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology | Year: 2011

In view of the inconvenience to obtain internal deformation of soil and other shortcomings in the existing shield model test, transparent soil is synthesized by means of calcium bromide solution and fused silica, the testing system of shield model is designed on this basis. Cutter head of shield machine model can be rotated, and also be retracted into the shield shell, and both are controlled with screw, this may be used to model shield tunneling and decreasing of support force at tunnel face. During shield tunneling the laser is used to illuminate the cross-section of transparent soil in front of the shield, the digital camera is used to capture the images continuously, internal soil deformations are calculated using particle image velocimetry. So the microscopic mechanism of tunneling induced soil deformation is visualized truly.

Pan H.,Chinese Academy of Sciences | Pan H.,CAS Chengdu Institute of Mountain Hazards and Environment | Huang J.,Yunnan University | Wang R.,State Key Laboratory of Geomechanics and Geotechnical Engineering | And 3 more authors.
Journal of Earth Science | Year: 2013

Debris flows are the one type of natural disaster that is most closely associated with human activities. Debris flows are characterized as being widely distributed and frequently activated. Rainfall is an important component of debris flows and is the most active factor when debris flows occur. Rainfall also determines the temporal and spatial distribution characteristics of the hazards. A reasonable rainfall threshold target is essential to ensuring the accuracy of debris flow pre-warning. Such a threshold is important for the study of the mechanisms of debris flow formation, predicting the characteristics of future activities and the design of prevention and engineering control measures. Most mountainous areas have little data regarding rainfall and hazards, especially in debris flow forming regions. Therefore, both the traditional demonstration method and frequency calculated method cannot satisfy the debris flow pre-warning requirements. This study presents the characteristics of pre-warning regions, included the rainfall, hydrologic and topographic conditions. An analogous area with abundant data and the same conditions as the pre-warning region was selected, and the rainfall threshold was calculated by proxy. This method resolved the problem of debris flow pre-warning in areas lacking data and provided a new approach for debris flow pre-warning in mountainous areas. © 2013 China University of Geosciences and Springer-Verlag Berlin Heidelberg.

Lu H.,Wuhan University | Liu Q.,Wuhan University | Liu Q.,State Key Laboratory of Geomechanics and Geotechnical Engineering | Chen C.,State Key Laboratory of Geomechanics and Geotechnical Engineering | Wu Y.,Wuhan University
Disaster Advances | Year: 2012

The hard and soft interbedding stratum is widely distributed in the Three Gorges reservoir area and the Sichuan basin. Many landslide hazards occurred in this kind of stratum and its disaster mechanism is very complex. In this paper, take the typical hard and soft interbedding slope as an example, we made laboratory test on the rock mass and established a geological model of the hard and soft interbedding slope. Furthermore, based on the slope stability analysis and considering creep properties of weak intercalated layer, the disaster mechanism is clarified and appropriate prevention measures are proposed. The research here can provide technical guidance for slope stability analysis in the Three Gorges reservoir area and the engineering safety in the construction of the western development.

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