ABSTRACT: In this study, a hydro-mechanical coupled algorithm is proposed to solve unsaturated soil problems in FLAC3D. The seepage model is extended using the in-built FISH language. The SWCC for unsaturated loess was best-fitted using MATLAB. The obtained parameters were written as a subroutine and invoked in each step in the seepage model to simulate seepage in unsaturated soil. Water infiltration at one-dimensional condition was modeled and compared using both the finite difference method and the finite element method, suggesting that the extension of the seepage model is appropriate. A non-linear elasto-plastic model was then defined to consider wetting induced variations in soil modulus and shear strength. Based on above improvement, a hydro-mechanical coupled analysis was performed to simulate sinkhole formation in unsaturated loess. The findings are meaningful in the investigation of the unsaturated soil theory and in the application of FLAC3D to simulate unsaturated soil problems.
Water has been recognized as a major cause of geological disasters in numerous cases, in forms of intense rainfall, irrigation, snowmelt, and water-level changes etc. Under natural conditions, soil exposing on slope, pit and tunnel is commonly at partially saturated state, which shows different properties with saturated soil in aspects of permeability, modulus and strength etc. (Fredlund & Rahardjo 1993, Mao 2003). Due to common existence of thick soil layers in field, it cannot obtain reasonable numerical results without consideration of the hydraulic and mechanical behaviors of unsaturated soil, especially for infiltration problems.
FLAC3D is a general finite difference program for modeling soil and rock behavior produced by Itasca (Itasca 2002). FLAC3D provides a flexible tool, i.e. the in-built FISH language, to solve complicated geotechnical problems. It has been applied to a broad range of projects and scientific research. However, the current standard FLAC3D cannot be used reasonably to analyze unsaturated soil problems due to absence of some constitutive equations. To overcome above limitation, a hydro-mechanical coupled algorithm is proposed for unsaturated soil in this study. The algorithm is verified firstly, and then applied to a field case of sinkhole formation in unsaturated loess layer.
Yu, G. M. (Qingdao Technological University) | Zang, X. G. (Blue Economic Zone Construction and Security, Collaborative Innovation Center) | Guo, Z. H. (Qingdao Technological University) | Kang, Y. (Blue Economic Zone Construction and Security, Collaborative Innovation Center) | Lu, S. B. (Qingdao Technological University)
ABSTRACT: Risk factors of buildings safety, taking a hotel as an example, induced by line 3 of Qingdao subway excavation are summarized based on detailed exploration and investigation of rock and soil mass properties underground, hydrological properties, tunnel excavation and support methods, building structure type and foundation form. Mechanism and development trend of various factors are studied under cavern. The characteristics and laws of influence factors are summarized. The degree of building damage and influence of various factors on building safety are predicted. Technical approach is studied to avoid the risk. Specific measures are proposed to control the risk. These results will provide a useful guidance for tunnel excavation of Qingdao and also in similar area.
Rock and soil mass surrounding a tunnel will be inevitably disturbed by tunnel excavation. The original equilibrium state of geotechnical body was destroyed. The original in situ stress will redistribute which leads to the subsidence and deformation of surface. Thereby, the safety of the existing buildings on the ground will be threatened. It should strictly control subsidence and deformation of the strata and the buildings on the ground for buildings safety when anomalies occur during tunnel excavation. Pre-recovery measures should be taken to control further damage to the buildings and ensure the structure safety when subsidence value and deformation value exceeds the allowable value. The practice shows that the grouting is one of the effective measures to reinforce strata, reduce strata subsidence and protect the existing buildings on the ground (Yuan 2010).
Taking a hotel as an example, the subsidence value of the building foundation is predicted based on numerical simulation respectively, without grouting, grouting in weak strata and grouting in weak strata and within 1 m above, Grouting effect of weak strata is analyzed.
Tan, W. H. (University of Science and Technology Beijing) | Jiang, X. H. (University of Science and Technology Beijing) | Li, J. (University of Science and Technology Beijing) | Xu, L. H. (University of Science and Technology Beijing)
ABSTRACT: Cohesion and friction angles are the main parameters determining rock strength and deformation. In open-pit mines, the shear strength parameters cohesive forces and friction angles of rock will decay with the excavation of mining and the time existence of slopes, and eventually reached to a stable value- long-term strength. The slopes of Shuichang iron open-pit mine were selected to analyze the stabilities and reinforcement by using three-Dimensional Distinct Element method. Results showed that the horizontal displacements at the upper of the slope increased dramatically when long-term strength parameters were considered than not, and the slope was instable. The slope will be stable with the reinforcement of anchor cables. Therefore, long-term strength parameters must be considered when analyze the stability of slopes in order to ensure the accuracy of the slope stability evaluation.
Slope stability analysis in open pit mines is always a long-term task accompanied with mining. As the development of mining, rock mass is unloaded and the mechanics parameters of rock mass changed with time. Thus, the characteristic of time-development of rock mass must be considered when the stability of the slope is analyzed and reinforcement is designed to provide a reasonable solution for reinforcement in open pit mines.
Shuichang iron open-pit mine of the Capital Iron Company is located in Qian'an City, Hebei Province, it is the main raw material base of the company. The lithologies of the slope are mainly composed of quaternary artificial deposits, breccia, magnetite, gneiss etc. A large number of engineering practices show that the strength parameters are time-dependent. The reason of strength reduction is the destruction of rock mass, the chemical and physical reaction and the change of environment.
The slope in zone II of Shuichang mine was selected as a case. Considering the long-term strength of rock mass, three-dimensional discrete element software was used to evaluate slopes deform at before and after reinforcement.
ABSTRACT: The damage degree and acoustic emission characteristics of coal sample are closely related to coal-rock dynamic destabilization. According to destructive test of large size coal sample from Huating coal mine, the damage and acoustic emission test of large size coal samples with stratification structure of parallel and vertical are completed. The coal-rock failure process and damage degree are described by the using of state vector, which can forecast the catastrophic and rupture. Based on the analysis of related index of state vector, the damage degree of percentage is defined, which quantitatively reflects the local damage and rupture intensity of rock mass. This has theory and practice significance for the prediction of large scale mining out area instability and derivative disasters in strong earthquake zone.
In Western of china, the mining area of Huating, Ning Dong and Shizuishan belong to the strong earthquake area, a large range of dynamic instability have occurred in the mining process, which is a serious challenge to the safety of coal mining in western mining area. Damage and fracture of Non uniform medium is a challenging problem in mechanics, such as the damage evolution does not follow the steady accumulation in the stage of destruction and disaster, the traditional uniform theory of continuum mechanics is difficult to deal with (Bai et al. 2006). The phenomenon of emission occurs in the deformation process for the brittle materials such as coal and rock (acoustic, emission, AE), so the AE technology can be used for monitoring internal damage of material under loading (Lavrov 2003, Rudajev et al. 2000). As the coal damage and deformation has the inner relativity with the dynamic instability, the analysis of acoustic emission characteristics in the process of damage and deformation has been paid much attention to forecasting dynamic disasters. In addition, the law and mechanism of temporal and spatial distribution for coal medium collapse mostly are analysed by using numerical simulation, theoretical analysis and the uniaxial compression tests of coal sample with small size on the assumption of uniform medium (Xu et al. 2004, Wang et al. 2003), which has made pioneering advances.
Ren, F. H. (University of Science and Technology Beijing) | Guo, Q. F. (University of Science and Technology Beijing) | Zheng, J. W. (Xi'an University of Science and Technology) | Lai, X. P. (Xi'an University of Science and Technology)
ABSTRACT: Mining-induced dynamic disasters caused by coal-rock mass destabilization in fault effect region are very common. Quantitative determination on the Ranging of Deeper Critical Destabilization (RDCD) of coal-rock mass is critically important for the supporting parameters optimization and mining safety. According to the safety mining idea in fault effect region of Tunbao Coal Mine, controlling parameters of coal-rock stability were confirmed by taking advantage of Hoek-Brown failure criterion theory, hence, the expression of RDCD was shown as R=k + a. In order to obtain the RDCD, a sight instrument was used to collect the optical information of hostrock around deep mining roadway, then the joint fractures' development characteristics and their distribution characteristics with depth could be predicted. So, based on the theoretical analysis and in-situ measurement, the RDCD in fault effect region was determinated, and the maximum RDCD reached 2.51 m. At last, an asymmetric supporting scheme was also proposed, which has been proved effective in roadway stability and safety.
In mining process, the faults will impact the layout of work plane and roadway, also, faults in the goaf influence stability of mining roadway. Along with the working face advance, stress concentration in front of the working face will aggravate the fault activation and migration, which may induce serious dynamic disasters. Wang Chuanying (Wang et al. 2010) proposed Rock Mass integrity Index (RMDI) method to describe rock mass integrity through borehole camera technology. Peng Suping and Meng Zhao ping (Peng et al. 2001, Men get al. 2001 & 2006) suggested that there are low stress area and high stress concentration zone in the fault and its surrounding zone. Kang Hongpu (Kang et al. 2010) used the borehole structure plane method to research the internal character of the coal and rock mass. Lai Xingping (Lai et al. 2008, Lai 2002) analyzed the damage and deformation of surrounding rock based on the monitoring data, and gave the reasonable supporting parameters. Li Shucai (Li et al. 2008) used the borehole TV camera to in-situ monitor the zonal disintegration phenomenon of surrounding rock mass and analyzed the relationship between zonal disintegration range and roadway radius.
Ma, L. J. (PLA University of Science and Technology, Nanjing) | Wang, G. A. (PLA University of Science and Technology, Nanjing) | Liu, X. Y. (PLA University of Science and Technology, Nanjing) | Yi, Q. K. (PLA University of Science and Technology, Nanjing) | Wang, Y. S. (PLA University of Science and Technology, Nanjing)
ABSTRACT: To consider the effect of intermediate principal stress on rock failure, the generalized Hoek-Brown criterion was modified by incorporating a new term to quantitatively account for the nonlinearity of rocks in high stress states. The failure envelope of the modified generalized as the Hoek-Brown criterion in the principal stress space is a curved hexagonal pyramid which touches the three outer apices of the original Hoek-Brown criterion. In the (σ1 – σ3) – (σ3 + nσ2) plane, it has a nonlinear form of powerlaw curve. The comparison results with three failure criteria based on multi-axial test strength data of four rocks indicate that the new three-dimensional Hoek-Brown criterion achieved the least misfit to most of the test data, followed by the Mogi (1971) criterion, whereas the Hoek-Brown and the Drucker-Prager criterion have a poor performance compared to the former two criteria. The modified Hoek-Brown criterion is proved to be a good candidate for prediction multi-axia strength of rocks.
The famous Hoek-Brown strength criterion was developed specially for geomaterials by trial error and based on a wide range of triaxial test data. It has been applied successfully to a wide range of intact and fractured rock types during the past three decades. While, the Hoek-Brown criterion was originally proposed without considering the influence of the intermediate principal stress and could not predict the true triaxial strength of rocks very well. As a matter of fact, much more evidence has proved that the intermediate principal stress does affect the rock strength in many instances (Mogi 1976, 1971, 1972). Pan & Hudson (1988) attempted to extend the two-dimensional Hoek-Brown criterion to a three-dimensional version by establishing the relationship between the octahedral shear stress and the first stress invariant. To take into account the effect of intermediate principal stress, Singh et al. (1998) suggested a new strength criterion by replacing σ2 with average confining pressure for highly anisotropic rock material and jointed rock masses. Zhang and Zhu proposed a three-dimensional Hoek-Brown criterion for rock mass by combining the general Mogi criterion and the original Hoek-Brown criterion (Zhang and Zhu 2007, Zhang 2008). The Zhang Zhu criterion was then developed into a generalized version and modified utilizing three different Lode dependences to solve the problems with some stress paths (Zhang et al. 2013).
Cao, S. F. (Beijing Research Institute of Uranium Geology) | Liu, Y. M. (Beijing Research Institute of Uranium Geology) | Xie, J. L. (Beijing Research Institute of Uranium Geology) | Ma, L. K. (Beijing Research Institute of Uranium Geology)
ABSTRACT: The design of High-Level radioactive Waste (HLW) repository in deep geological media shows that the highly compacted bentonite is a kind of ideal buffer material. Buffer materials between waste tank and the surrounding geological body is the last artificial barrier neighboring waste. The coupled Thermo-Hydro-Mechanical (THM) behaviors of the compacted bentonite are of importance for the HLW repository when operation and closed. This mock-up test was carried out to investigate the properties under THM coupled conditions, which will be helpful for the future design of engineered barrier system of China-mock-up. The characterization of compacted GaoMiaoZi (GMZ) bentonite related to swelling pressure, relative humidity and temperature are presented and interpreted.
The deep geological disposal for High-Level radioactive Waste (HLW) has been considered as an urgent worldwide environment issue. China pays more and more attentions to nuclear waste with the development of great economical growth. The long-term and reliable insulation from the human environment has raised worldwide attention for the countries who build nuclear power stations. Safe disposal of high level radioactive waste is a challenging task facing the scientific and technological world (Wang et al. 2006a). In order to safely dispose of the high-level radioactive waste generated from the nuclear power plants and other nuclear facilities, a number of disposal concepts have been developed in many countries, and results show that the deep geological disposal of High-Level radioactive Waste (HLW) is considered worldwide as the most safe and feasible method to protect human being and environment for tens of thousands years (Zhang et al. 2006). The behavior of HLW repository is determined, to a large extent, by the characteristics of the design and construction of the engineered barriers and especially by the changes that may occur in the mechanical, hydraulic, and geochemical properties as a result of the combined effects of heat generated by the radioactive decay and of the water and solutes supplied the surrounding rock (Villar et al. 2012). The concept design of repository in different geological formations generally relies on a multi-barrier system, which typically comprises the natural geological barriers provided by the repository host rock and an engineered barrier system (Liu & Wen 2003; Wang 2010).
ABSTRACT: In recent decade, geophysical methods, such as microseismic monitoring, geotomography, and in-seam seismic techniques, have shown an increased significance in rock physical mechanics and mining engineering. Especially the developments of seismic monitoring bring hope to predict the rock burst and seismic hazards, where potential location determination of hypocenter is the key technology. In previous study, the location techniques all need two hypotheses: l) The propagation speed can be measured accurately; 2) Seismic wave propagates in homogeneous, isotropic geological structures. While in practical applications, heterogeneous geological structure makes the medium (what the seismic wave propagation) shows anisotropic feature instead of isotropic. Meanwhile measuring the propagation speed accurately is very difficult. In order to solve these two problems, localization method of microseismic source based on the genetic algorithm without pre-measuring speed is proposed. This method assumes that the seismic wave propagates in the direction of a spindle, and the propagation speed is the fastest along the spindle direction. The equations are established in which the source position, propagation speed and spindle orientation are variables. Finally, the equations were solved through genetic algorithm. The comparison between the predict results by our method and the experimental data measured in DongGua Copper showed that the proposed method can predict the source location more accurately, and with a good prospect.
In the practice of mining and underground geotechnical engineering, the breaking of rock under high stress is always accompanied by the releasing and propagation of seismic wave. While the corresponding microseismic events have occurred, a large number of information about rock damage can be defected (Fagan et al. 2013, Chen et al. 2014). Therefore, the rock internal behavior and rockburst and other mining disasters can be inferred by a process that contains microseismic signal acquisition, processing, analysis and research. The results can help us to preventing seismic hazards; ensure the safety of deep geotechnical engineering (Wang & Ge 2008, Chen 2009).
ABSTRACT: The study concentrates on the safety factors involved in rock slope stability of an open-pit porphyry copper mine. The analysis of the safety factors are based on the comparison of different optimized slope angles and the slope stability in different geological zones is also included in the research. By applying the methods of Flac3d and the limit equilibrium analysis, it can determine the possible failure zone and reasonable slope angle for open-pit mining. The conclusion is a great contribution to the following mining design and further production practice for open pit mining.
1 SURVEY OF MINING AREA
The mining area is located in the oblique east wing of the back of Xibeikulasi, and is relatively flat, which belongs to the low mountain hilly terrain. The altitude is 770 meters, the relative elevation is generally of 5 to 15 meters, and the scope of mineralization is an oval area with the length and width of about 1.0 km. The exposed stratum is Xibeikulasi Shangya Formation (C1X2) and Baogutu Xiaya Formation (C1B1) of Lower Carboniferous Series. The stratum is in nearly north-south direction, with tendency to the east and the dip angle of 60° to 70°.
2 SLOPE ROCK MASS QUALITY CHARACTERISTICS
The partition of the geology of the copper mine project is taken according to the surrounding topography and lithology around the area, combined with field geological survey and additional exploration results. During the partition, the hydrogeological conditions, fault joints and the engineering factors and geological factors of the crushed zone have been overall considered. The strip mine is divided into six.
Liu, X. Y. (State Nuclear Electric Power Planning, Design and Research Institute, Beijing) | Cai, W. (State Nuclear Electric Power Planning, Design and Research Institute, Beijing) | Wang, Y. (Jiangsu Nuclear Power Co. Ltd.)
ABSTRACT: Debris flow caused by the landside is one of complicated geologic hazards in mountain area, which is closely associated with geology, lithology, the mechanical characteristics of the rock and soil, rainfall, groundwater and land usage condition etc. The analysis of immanent relationships between landslide and Debris flow can not only provide some important information about landslide failure mechanism, but also be used as the basis of evaluation of Debris flow triggered by landslides. In this paper, the depth integral was applied in two-dimensional mathematical model of Debris flow which is based on the principle of conservation of mass and viscous Newtonian fluid Navier-Stovkes equation. Then, this equation was numerically computed by using the finite difference method. The relational expression between streams tilt angle and the width of affected range of Debris flow, which is obtained from statistics, was applied to analyse the possibility of Debris flow induced by landslides which once failed under the similar geological conditions. Combining with GIS, the model can also be used to predict impacted range of Debris flow by using risk map to show the zones that may be affected by the Debris flow.
Majority Debris flows usually happen after the occurrence along stem from the landside by the rainfall. They are results of the area of the landslides advanced to valley. The debris flows have the characteristics of sudden eruption, intermittent and enormous energy. Because of the destructive power, the debris flow may cause heavy casualties and serious economic losses. Therefore, the prediction of disaster area and motion trajectory has already become one of the most important the risk assessment. Geographic information system and digital model has become a practical and effective means in analyzing geologic hazard. These two techniques have strong treatment ability of spatial data and the attribute data, and can also be efficiently solved in data collecting, data processing, and data analysis about landslide and debris flow. By the method of the interaction between sensitivity factor of spatial distribution and digital model to assess to the hazard of the debris flow gully become hot spot.