2010-04期论文电子版 [复制链接]

Ming Lu^*
SINTEF Rock Engineering, Trondheim, Norway
Received 13 October 2010; received in revised form 13 November 2010; accepted 20 November 2010

Abstract: Oil and gas can be stored underground by a variety of means, such as in depleted oil and gas fields, in aquifers, in rock salt caverns, in unlined mined rock caverns, in lined shallow caverns and abandoned mines. Different types of underground storages require different geological and hydrogeological conditions and are associated with different rock engineering problems. However, the common issue is to ensure the gas- and oil-tightness of storage caverns. In other words, the stored oil and gas must not escape from the storage caverns. This may be realized by different means according to the types of storages and the sites geological conditions. There are basically two approaches of gas leakage control, i.e. permeability control and hydrodynamic containment. The latter involves the use of a water curtain system in many cases, which creates an artificial hydraulic boundary condition and helps to establish the required groundwater condition when needed. In addition to the common problems, the underground storage of liquefied petroleum gas (LPG) requires special attentions to the opening of rock joints, which result from the tensile thermal stress induced by the low storage temperature. Great care must be taken in choosing abandoned mines for oil and gas-storage since it is quite rare that the natural site conditions can meet the usual requirements, in particular for the gas tightness. The paper provides a general description of the gas leakage control for underground oil and gas storage projects, and addresses various rock engineering problems associated with selected types of storages in detail.

Key words: oil storage; gas storage; rock cavern; rock mechanics; gas leakage

A study of jacking force for a curved pipejacking

K. J. Shou, J. M. Jiang
Department of Civil Engineering, National Chung Hsing University, Taichung, China
Received 25 August 2010; received in revised form 30 October 2010; accepted 8 November 2010


Abstract: For a pipejacking, the jacking force is critical to balance the resistance force and to move the pipe string forwards. The driving mechanism of a curved pipejacking is more complicated than a straight-line pipejacking, and its jacking force is also more difficult to be determined. The paper theoretically studies the jacking force of a curved pipejacking by considering the static equilibrium of earth pressure, resistance at cutting face, friction at pipe surface, and the driving force behind the pipe string. The derived theoretical formula can be used to estimate the driving forces of a straight-line or a curved pipejacking. Case study was performed by applying the theoretical and empirical formulae. After calibration, the corrected formula is more accurate and more applicable.
Key words: pipejacking; curved pipejacking; jacking force; statics analysis

Stability and reinforcement analyses of high arch dams by considering deformation effects

Qiang Yang, Yaoru Liu, Yingru Chen, Weiyuan Zhou
State Key Laboratory of Hydroscience and Hydraulic Engineering, Tsinghua University, Beijing, 100084, China
Received 5 September 2010; received in revised form 8 October 2010; accepted 15 October 2010


Abstract: The strict definition and logical description of the concept of structure stability and failure are presented. The criterion of structure stability is developed based on plastic complementary energy and its variation. It is presented that the principle of minimum plastic complementary energy is the combination of structure equilibrium, coordination condition of deformation and constitutive relationship. Based on the above arguments, the deformation reinforcement theory is developed. The structure global stability can be described by the relationship between the global degree of safety of structure and the plastic complementary energy. Correspondingly, the new idea is used in the evaluations of global stability, anchorage force of dam-toe, fracture of dam-heel and treatment of faults of high arch dams in China. The results show that the deformation reinforcement theory provides a uniform and practical theoretical framework and a valuable solution for the analysis of global stability, dam-heel cracking, dam-toe anchorage and reinforcement of faults of high arch dams and their foundations.
Key words: deformation reinforcement theory; structure stability; unbalanced force; plastic complementary energy; high arch dams

Chemo-mechanical couplings in compacted argillite submitted to high-pH environment

O. Cuisinier, F. Masrouri
LAEGO, Nancy Université, Nancy, France
Received 16 October 2010; received in revised form 5 November 2010; accepted 10 November 2010


Abstract: In the French concept of deep nuclear wastes repository, the galleries should be backfilled with excavated argillite after the site exploitation period. After several thousands of years, the degradation of the concrete lining of the galleries will generate alkaline fluid (pH > 12) that will diffuse through the backfill. The objective of the paper is to describe the influence of such solute diffusion on the microstructure and the mechanical behavior of compacted argillite. Saturated-portlandite water was circulated through compacted samples for 3, 6 and 12 months at 20 °C or 60 °C, respectively. The microstructures before and after fluid circulation were determined with mercury intrusion porosimetry. Since it was planned to introduce additives (bentonite or lime) in the remoulded argillite to backfill the deep galleries, such mixtures were also studied. The results show that the influence of the alkaline fluid on the properties of the argillite is a function of the nature of the additive. The pure argillite undergoes slight modifications that can be related to a limited dissolution of its clayey particles. Conversely, intense alteration of the bentonite-argillite mixture was observed. Lime addition improves the mechanical characteristics of the argillite through the precipitation of cementitious compounds.  

Key words: chemo-mechanical couplings; alkaline plume; argillite; microstructure; shear strength

Jianchun Li1, Haibo Li1, Guowei Ma2

1 State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071, China
2 School of Civil and Resource Engineering, University of Western Australia, Crawley, 6009, Australia
Received 10 August 2010; received in revised form 15 September 2010; accepted 28 October 2010


Abstract: Seismic wave interaction with a slippery rock joint with an arbitrary impinging angle is analytically studied based on the conservation of momentum on the wave fronts. Based on the displacement discontinuity method, the wave propagation equations are derived for incident P- and S-waves. By comparison, the calculated transmission and reflection coefficients for normal incident waves are the same as the existing results, which proves the wave propagation equation obtained in the paper is correct. The wave propagation derived in the context can be applied to incident waves with different waveforms. Stochastic seismic waves are then used to analyze the seismic wave interaction with the slippery rock joint, where the stochastic seismic waves are generated from frequency spectra. The parametric studies are carried out to investigate the effect of type, intensity and impinging angle of the incident seismic waves on the wave propagation across the slippery rock joint.
Key words: stochastic seismic wave; slippery rock joint; wave propagation; wave fronts; conservation of momentum

Phenomena and theoretical analysis for the failure of brittle rocks

Faquan Wu1, Jie Wu2*, Shengwen Qi1
1 Key Laboratory of Engineering Geomechanics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
2 Engineering College, China University of Geosciences, Wuhan, 430074, China
Received 8 October 2010; received in revised form 8 November 2010; accepted 15 November 2010


Abstract: Rockburst, an unstable failure of brittle rocks, has been greatly concerned in rock mechanics and rock engineering for more than 100 years. The current understanding on the mechanical mechanism of rockburst is based on the Coulomb theory, i.e. compressive-shear failure theory. This paper illustrates a series of tensile and tensile-shear fracture phenomena of rockburst, and proposes a methodology for the analysis of fracture mode and its energy dissipation process based on Griffith theory. It is believed that: (1) the fracture modes of rockburst should include compressive-shear, tensile-shear and pure tensile failures; (2) the rupture angle of rock mass decreases with the occurrence of tensile stress; (3) the proportion of kinetic energy in the released strain energy from a rockburst may be much larger than that transferred into surface energy; and (4) the understanding on the tensile and tensile-shear failure modes of rockburst may change the basic thinking of rockburst control, i.e. from keeping the reduction in initial compressive stress   to restricting the creation of secondary tensile stress.

Key words: failure of brittle rock; tensile-shear fracture; Griffith criterion; released strain energy; kinetic energy

Considerations of rock dilation on modeling failure and deformation of hard rocks—a case study of the mine-by test tunnel in Canada

Xingguang Zhao1*, Meifeng Cai2, M. Cai3
1 Beijing Research Institute of Uranium Geology, Beijing, 100029, China
2 School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
3 School of Engineering, Laurentian University, Sudbury, P3E 2C6, Canada
Received 10 October 2010; received in revised form 30 October 2010; accepted 5 November 2010


Abstract: For the compressive stress-induced failure of tunnels at depth, rock fracturing process is often closely associated with the generation of surface parallel fractures in the initial stage, and shear failure is likely to occur in the final process during the formation of shear bands, breakouts or V-shaped notches close to the excavation boundaries. However, the perfectly elastoplastic, strain-softening and elasto-brittle-plastic models cannot reasonably describe the brittle failure of hard rock tunnels under high in-situ stress conditions. These approaches often underestimate the depth of failure and overestimate the lateral extent of failure near the excavation. Based on a practical case of the mine-by test tunnel at an underground research laboratory (URL) in Canada, the influence of rock mass dilation on the depth and extent of failure and deformation is investigated using a calibrated cohesion weakening and frictional strengthening (CWFS) model. It can be found that, when modeling brittle failure of rock masses, the calibrated CWFS model with a constant dilation angle can capture the depth and extent of stress-induced brittle failure in hard rocks at a low confinement if the stress path is correctly represented, as demonstrated by the failure shape observed in the tunnel. However, using a constant dilation angle cannot simulate the nonlinear deformation behavior near the excavation boundary accurately because the dependence of rock mass dilation on confinement and plastic shear strain is not considered. It is illustrated from the numerical simulations that the proposed plastic shear strain and confinement-dependent dilation angle model in combination with the calibrated CWFS model implemented in FLAC can reasonably reveal both rock mass failure and displacement distribution in vicinity of the excavation simultaneously. The simulation results are in good agreement with the field observations and displacement measurement data.  
Key words: hard rocks; brittle failure; deformation; dilation angle model; confinement; plastic shear strain; mine-by test tunnel

Three independent parameters to describe conventional triaxial compressive strength of intact rocks

Mingqing You
School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, 454010, China
Received 28 October 2010; received in revised form 20 November 2010; accepted 1 December 2010


Abstract: The strengths of 12 rocks cited from literatures increase in a nonlinear way with increasing confining pressure against the Coulomb criterion. The criteria with power forms like the generalized Hoek-Brown criterion are not available for describing the strength properties in the whole test range for Indiana limestone, Yamaguchi marble and Vosges sandstone, of which the differential stresses are approximately constant at high confining pressures. The exponential criterion with three parameters fits the test data of those 12 rocks well with a low misfit. The three parameters are independent of the uniaxial compressive strength (UCS), the initial increasing rate of strength with confining pressure, and the limitation of differential stress.
Key words: strength criteria; criterion parameters; exponential criterion; intact rocks

Research on unloading nonlinear mechanical characteristics of jointed rock masses

Jianlin Li1, Lehua Wang1, Xingxia Wang1, 2, Ruihong Wang1, Zhuang Cheng1, Li Dang1
1 Key Laboratory of Geological Hazards for Three Gorges Reservoir Area of Ministry of Education, China Three Gorges University, Yichang, 443002, China
2 College of Hydraulic and Environmental Engineering, China Three Gorges University, Yichang, 443002, China
Received 12 October 2010; received in revised form 5 November 2010; accepted 16 November 2010


Abstract: Geological environments of rock mass projects are always very complicated, and further investigations on rock mechanical characteristics are needed. There are considerable distinctions in rock mechanical characteristics under unloading and loading conditions. A series of tests are conducted to study the stress-strain relationship of rock masses under loading and unloading conditions. Also, the anisotropy, the size effect, and the rheological property of unloading rock mass are investigated. The tests presented in the paper include model test and granite rheological test, which are conducted considering geological condition, rock mass structure, in-situ stress field of the permanent shiplock of the Three Gorges Project. The main differences between loading and unloading rock masses are stress paths, yield criteria, deformation and strength parameters, etc.. Different structural plane directions affect unloading rock mass evidently. With increasing size, the tensile strength, the compressive strength, the deformation modulus, the Poisson’s ratio and the anisotropy of rock mass all decrease. For sandstone samples with parallel bedding planes, the cohesion c increases but the internal friction angle   decreases under unloading condition when compared with the values under loading condition. While for samples with vertical bedding planes, the trend is adverse. The rheological property of rocks has close relationship with the tensile stresses of rock masses. When the sandstone samples are tested under high stress condition, their rheological properties are very obvious with the unloading of confining pressure, and three typical rheological stages are shown. Rheological rate changes with the variations in axial stress and confining pressure.
Key words: unloading rock mass; unloading test; anisotropy of rock mass; size effect; rheological rate

Improvement of silty clay by vacuum preloading incorporated with electroosmotic method

Baotian Wang1, M. Q. Vu2
1 Institute of Geotechnical Engineering, Hohai University, Nanjing, 210098, China
2 Department of Soil Mechanics and Foundation Engineering, National University of Civil Engineering, Hanoi, Vietnam
Received 2 June 2009; received in revised form 18 September 2010; accepted 10 October 2010


Abstract: A laboratory test was performed to assess the effectiveness of vacuum preloading incorporated with electroosmotic (EOM) treatment on silty clay (combined method) for reclamation projects like new disposal ponds, where the horizontal electrode configurations beneath the soil layer were possible and the drainage pipes and the prefabricated vertical drains (PVDs) system could be easily installed in advance before the sludge dragged from sea bed or river bed was filled into the site. Three groups of tests were conducted on the silty clay from Qinhuai River in Nanjing, China. The model is able to apply vacuum pressure at the bottom of the soil layer and a direct current electric field simultaneously. It is also possible to measure the pore pressures at different depths of soil column, and the changes in settlement and volume with the elapsed time. In this study, the vacuum preloading method, vacuum preloading applied at the bottom (VAB method), was applied and the cathodes were installed beneath the soil layer. The results obtained indicate substantial reduction in water content, and increases in dry density and undrained shear strength in comparison with those obtained by the vacuum preloading only, particularly at the positions close to the anode. The combined method utilizes the vertical drainage flow created by the electroosmosis integrating the horizontal drainage flow created mostly by the vacuum pressure. The total drainage flow can be calculated as a result of the vertical drainage flow by electroosmosis only and the horizontal drainage flow by the vacuum preloading only. The way of placement of the cathode and the anode in the combined method also overcomes the disadvantage of EOM method itself, i.e. the appearance of cracks between the anode and the surrounding soil. Moreover, it is observed that the vacuum preloading plays a primary role in earlier stage in deduction of free pore water; meanwhile, the electroosmotic method is more efficient in later stage for absorbing water in the diffused double layers of soil.
Key words: vacuum preloading; VAB method; soil improvement; consolidation; pore pressure; undrained shear strength; dry density; electroosmotic method

Numerical simulation of dynamic response of operating metro tunnel induced by ground explosion

Yubing Yang1, Xiongyao Xie1*, Rulu Wang2
1 Key Laboratory of Geotechnical Engineering, Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China
2 Shanghai Metro Operation Co., Ltd., Shanghai, 200003, China
Received 10 October 2010; received in revised form 28 October 2010; accepted 10 November 2010


Abstract: To evaluate the effects of possible ground explosion on a shallow-buried metro tunnel, this paper attempts to analyze the dynamic responses of the operating metro tunnel in soft soil, using a widely applied explicit dynamic nonlinear finite element software ANSYS/LS-DYNA. The blast induced wave propagation in the soil and the tunnel, and the von Mises effective stress and acceleration of the tunnel lining were presented, and the safety of the tunnel lining was evaluated based on the failure criterion. Besides, the parametric study of the soil was also carried out. The numerical results indicate that the upper part of the tunnel lining cross-section with directions ranging from 0 to 22.5° and horizontal distances 0 to 7 m away from the explosive center are the vulnerable areas, and the metro tunnel might be safe when tunnel depth is more than 7 m and TNT charge on the ground is no more than 500 kg, and the selection of soil parameters should be paid more attentions to conduct a more precise analysis.
Key words: ground surface explosion; numerical simulation; metro tunnel; dynamic response

林编辑辛苦了
非常感谢！