2010-03期电子版文档 [复制链接]

Preliminary engineering application of microseismic monitoring technique to rockburst prediction in tunneling of Jinping II project

Chun’an Tang^1*, Jimin Wang², Jingjian Zhang^3
1 School of Civil Engineering, Dalian University of Technology, Dalian, 116024, China
² Jinping Construction Management Authority, Ertan Hydropower Development Co., Ltd., Xichang, 615012, China
³ School of Hydraulic Engineering, North China Institute of Water Conservancy and Hydroelectric Power, Zhengzhou, 450011, China
Received 2 August 2010; received in revised form 15 August 2010; accepted 20 August 2010
      

Abstract: Monitoring and prediction of rockburst remain to be worldwide challenges in geotechnical engineering. In hydropower, transportation and other engineering fields in China, more deep, long and large tunnels have been under construction in recent years and underground caverns are more evidently featured by “long, large, deep and in group”, which bring in many problems associated with rock mechanics problems at great depth, especially rockburst. Rockbursts lead to damages to not only underground structures and equipments but also personnel safety. It has been a major technical bottleneck in future deep underground engineering in China. In this paper, compared with earthquake prediction, the feasibility in principle of monitoring and prediction of rockbursts is discussed, considering the source zones, development cycle and scale. The authors think the feasibility of rockburst prediction can be understood in three aspects: (1) the heterogeneity of rock is the main reason for the existence of rockburst precursors; (2) deformation localization is the intrinsic cause of rockburst; and (3) the interaction between target rock mass and its surrounding rock mass is the external cause of rockburst. As an engineering practice, the application of microseismic monitoring techniques during tunnel construction of Jinping II Hydropower Station was reported. It is found that precursory microcracking exists prior to most rockbursts, which could be captured by the microseismic monitoring system. The stress concentration is evident near structural discontinuities (such as faults or joints), which shall be the focus of rockburst monitoring. It is concluded that, by integrating the microseismic monitoring and the rock failure process simulation, the feasibility of rockburst prediction is expected to be enhanced.

Key words: microseismic monitoring; numerical modeling; rockburst; prediction

2010-03-01.pdf (2341 K) 下载次数:341

A new classification of seepage control mechanisms in geotechnical engineering

Yifeng Chen1, 2, Ran Hu1, 2, Chuangbing Zhou1, 2*, Dianqing Li1, 2, Guan Rong1, 2, Qinghui Jiang1, 2
1 State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China
2 Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of Ministry of Education, Wuhan University, Wuhan, 430072, China
Received 14 July 2010; received in revised form 1 September 2010; accepted 6 September 2010


Abstract: Seepage flow through soils, rocks and geotechnical structures has a great influence on their stabilities and performances, and seepage control is a critical technological issue in engineering practices. The physical mechanisms associated with various engineering measures for seepage control are investigated from a new perspective within the framework of continuum mechanics; and an equation-based classification of seepage control mechanisms is proposed according to their roles in the mathematical models for seepage flow, including control mechanisms by coupled processes, initial states, boundary conditions and hydraulic properties. The effects of each mechanism on seepage control are illustrated with examples in hydroelectric engineering and radioactive waste disposal, and hence the reasonability of classification is demonstrated. Advice on performance assessment and optimization design of the seepage control systems in geotechnical engineering is provided, and the suggested procedure would serve as a useful guidance for cost-effective control of seepage flow in various engineering practices.
Key words: seepage flow; seepage control mechanisms; optimization design; coupled processes; initial states; boundary conditions; hydraulic properties

2010-03-02.pdf (4811 K) 下载次数:74

A new early-warning prediction system for monitoring shear force of fault plane in the active fault

Manchao He1, 2, Yu Wang1, 2, Zhigang Tao1, 2
1 Research Center of Geotechnical Engineering, China University of Mining and Technology, Beijing, 100083, China
2 State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing, 100083, China
Received 29 June 2010; received in revised form 20 August 2010; accepted 10 September 2010


Abstract: The most common method used to describe earthquake activity is based on the changes in physical parameters of the earth’s surface such as displacement of active fault and seismic wave. However, such approach is not successful in forecasting the movement behaviors of faults. In the present study, a new mechanical model of fault activity, considering the shear strength on the fault plane and the influence of the resistance force, is established based on the occurrence condition of earthquake. A remote real-time monitoring system is correspondingly developed to obtain the changes in mechanical components within fault. Taking into consideration the local geological conditions and the history of fault activity in Zhangjiakou of China, an active fault exposed in the region of Zhangjiakou is selected to be directly monitored by the real-time monitoring technique. A thorough investigation on local fault structures results in the selection of two suitable sites for monitoring potential active tectonic movements of Zhangjiakou fault. Two monitoring curves of shear strength, recorded during a monitoring period of 6 months, turn out to be steady, which indicates that the potential seismic activities hardly occur in the adjacent region in the near future. This monitoring technique can be used for early-warning prediction of the movement of active fault, and can help to further gain an insight into the interaction between fault activity and relevant mechanisms.
Key words: active faults monitoring; earthquake; early-warning system; shear strength

2010-03-03.pdf (1982 K) 下载次数:62

Predicting geological hazards during tunnel construction

Shucai Li*, Shuchen Li, Qingsong Zhang, Yiguo Xue, Bin Liu, Maoxin Su, Zhechao Wang, Shugang Wang
Geotechnical and Structural Engineering Research Center, Shandong University, Jinan, 250061, China
Received 15 June 2010; received in revised form 2 July 2010; accepted 15 July 2010

Abstract: The complicated geological conditions and geological hazards are challenging problems during tunnel construction, which will cause great losses of life and property. Therefore, reliable prediction of geological defective features, such as faults, karst caves and groundwater, has important practical significances and theoretical values. In this paper, we presented the criteria for detecting typical geological anomalies using the tunnel seismic prediction (TSP) method. The ground penetrating radar (GPR) signal response to water-bearing structures was used for theoretical derivations. And the 3D tomography of the transient electromagnetic method (TEM) was used to develop an equivalent conductance method. Based on the improvement of a single prediction technique, we developed a technical system for reliable prediction of geological defective features by analyzing the advantages and disadvantages of all prediction methods. The procedure of the application of this system was introduced in detail. For prediction, the selection of prediction methods is an important and challenging work. The analytic hierarchy process (AHP) was developed for prediction optimization. We applied the newly developed prediction system to several important projects in China, including Hurongxi highway, Jinping II hydropower station, and Kiaochow Bay subsea tunnel. The case studies show that the geological defective features can be successfully detected with good precision and efficiency, and the prediction system is proved to be an effective means to minimize the risks of geological hazards during tunnel construction.
Key words: tunnel projects; geological hazards; comprehensive prediction; tunnel seismic prediction (TSP); ground penetrating radar (GPR); transient electromagnetic method (TEM); analytic hierarchy process (AHP)

2010-03-04.pdf (598 K) 下载次数:93

Evaluation of hydrodynamic dispersion parameters in fractured rocks

Zhihong Zhao1, Lanru Jing1, Ivars Neretnieks2
1 Department of Land and Water Resources Engineering, Royal Institute of Technology, Stockholm SE-100 44, Sweden
2 Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm SE-100 44, Sweden
Received 10 August 2010; received in revised form 28 August 2010; accepted 10 September 2010


Abstract: A numerical procedure to determine the equivalent hydrodynamic dispersion coefficients and Péclet number (Pe) of a fractured rock is presented using random walk particle tracking method. The geometrical effects of fracture system on hydrodynamic dispersion are studied. The results obtained from the proposed method agree well with those of empirical models, which are the scale-dependent hydrodynamic dispersion coefficients in an asymptotic or exponential form. A variance case is added to investigate the influence of longitudinal hydrodynamic dispersion in individual fractures on the macro-hydrodynamic dispersion at the fracture network scale, and its influence is demonstrated with a verification example. In addition, we investigate the influences of directional flow and stress conditions on the behavior of hydrodynamic dispersion in fracture networks. The results show that the magnitudes of the hydrodynamic dispersion coefficients are relatively smaller when the flow direction is parallel to the dip directions of fracture sets. Compressive stresses significantly reduce hydrodynamic dispersion. However, the remaining questions are: (1) whether the deformed fracture network under high stress conditions may make the scale-dependent hydrodynamic dispersion coefficients have asymptotic or exponential forms, and (2) what the conditions for existence of a well-defined equivalent hydrodynamic dispersion tensor are. They need to be further investigated.
Key words: hydrodynamic dispersion; Péclet number (Pe); fracture networks; stress effects

2010-03-05.pdf (1586 K) 下载次数:59

Temperature-controlled triaxial compression/creep test device for thermodynamic properties of soft sedimentary rock and corresponding theoretical prediction

Sheng Zhang1, Hirotomo Nakano2, Yonglin Xiong2, Tomohiro Nishimura2, Feng Zhang2
1 School of Civil Engineering and Architecture, Central South University, Changsha, 410083, China
2 Department of Civil Engineering, Nagoya Institute of Technology, Nagoya, 4668555, Japan
Received 15 August 2010; received in revised form 30 August 2010; accepted 5 September 2010


Abstract: In deep geological disposal of high-level nuclear waste, one of the most important subjects is to estimate long-term stability and strength of host rock under high temperature conditions caused by radioactive decay of the waste. In this paper, some experimental researches on the thermo-mechanical characteristics of soft sedimentary rock have been presented. For this reason, a new temperature-controlled triaxial compression and creep test device, operated automatically by a computer- controlled system, whose control software has been developed by the authors, was developed to conduct the thermo-mechanical tests in different thermal loading paths, including an isothermal path. The new device is proved to be able to conduct typical thermo-mechanical element tests for soft rock. The test device and the related testing method were introduced in detail. Finally, some test results have been simulated with a thermo-elasto-viscoplastic model that was also developed by the authors.
Key words: temperature control; soft sedimentary rock; thermal triaxial compression test; thermal triaxial creep test

2010-03-06.pdf (1588 K) 下载次数:57

Numerical modeling of coupled thermo-mechanical response of a rock pillar

Yifeng Chen1, 2*, Chuangbing Zhou1, 2, Lanru Jing3
1 State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China
2 Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of Ministry of Education, Wuhan University, Wuhan, 430072, China
3 Department of Land and Water Resources Engineering, Royal Institute of Technology, Stockholm SE-100 44, Sweden
Received 14 August 2010; received in revised form 5 September 2010; accepted 12 September 2010


Abstract: Understanding the rock mass response to excavation and thermal loading and improving the capability of the numerical models for simulating the progressive failure process of brittle rocks are important for safety assessment and optimization design of nuclear waste repositories. The international cooperative DECOVALEX-2011 project provides a platform for development, validation and comparison of numerical models, in which the Äspö pillar stability experiment (APSE) was selected as the modeling target for Task B. This paper presents the modeling results of Wuhan University (WHU) team for stages 1 and 2 of Task B by using a coupled thermo-mechanical model within the framework of continuum mechanics. The rock mass response to excavation is modeled with linear elastic, elastoplastic and brittle-plastic models, while the response to heating is modeled with a coupled thermo-elastic model. The capabilities and limitations of the model for representation of the thermo- mechanical responses of the rock pillar are discussed by comparing the modeling results with experimental observations. The results may provide a helpful reference for the stability and safety assessment of the hard granite host rock in China’s Beishan preselected area for high-level radioactive waste disposal.
Key words: thermo-mechanical coupling; Äspö pillar stability experiment (ASPE); numerical modeling; DECOVALEX-2011 project

2010-03-07.pdf (356 K) 下载次数:70

Sensitivity and inverse analysis methods for parameter intervals

Guojian Shao1, Jingbo Su2
1 Department of Engineering Mechanics, Hohai University, Nanjing, 210098, China
2 College of Harbor, Coastal and Offshore Engineering, Hohai University, Nanjing, 210098, China
Received 30 April 2010; received in revised form 15 June 2010; accepted 25 June 2010


Abstract: This paper proposes a sensitivity analysis method for engineering parameters using interval analyses. This method substantially extends the application of interval analysis method. In this scheme, parameter intervals and decision-making target intervals are determined using the interval analysis method. As an example, an inverse analysis method for uncertainty is presented. The intervals of unknown parameters can be obtained by sampling measured data. Even for limited measured data, robust results can also be obtained with the inverse analysis method, which can be intuitively evaluated by the uncertainty expressed in terms of an interval. For complex nonlinear problems, an iteratively optimized inverse analysis model is proposed. In a given set of loose parameter intervals, all the unknown parameter intervals that satisfy the measured information can be obtained by an iteratively optimized inverse analysis model. The influences of measured precisions and the number of parameters on the results of the inverse analysis are evaluated. Finally, the uniqueness of the interval inverse analysis method is discussed.
Key words: interval analysis method; sensitivity analysis; reversible inverse analysis method; iteratively optimized inverse analysis method

2010-03-08.pdf (151 K) 下载次数:62

Stability of roadways in coalmines alias rock mechanics in practice

Richard Šňupárek, Petr Konečný
Institute of Geonics, Academy of Sciences of Czech Republic, Brno 60200, Czech Republic
Received 23 June 2010; received in revised form 28 August 2010; accepted 8 September 2010


Abstract: This paper describes the procedures for design of supports and stabilization measures in the roadways. The procedures are based on the system developed in Ostrava-Karvina coal basin in Czech Republic. The calculation of load bearing capacity of roadway supports contains the period of roadway construction and mining in the vicinities, based on the size of the natural rock arch. The loading of supports during mining comes from a stress wave in the rock mass in the forefront of coalface and the caving area of mined-out panel. The input data for the calculation method are deduced according to in-situ measurements of convergence and displacement in the roadways.
Key words: coalmines; roadways; stability; support; bolting


2010-03-09.pdf (1544 K) 下载次数:77

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