Probabilistic assessment of rock slopes stability using the response surface approach——A case study

This paper examines the stability condition of a jointed rock slope in the south western region of Saudi Arabia using deterministic and probabilistic approaches, under both dry and wet conditions. The study area is characterized by complex geology in rugged terrains. The stability analysis is carried out using the code FLAC3 D to generate a 3-dimensional, ubiquitous joint model, to determine the influence of the dominant, unfavourable discontinuity orientation with respect to the slope face. The deterministic analysis is first implemented using the mean values of the selected random variables, namely the dip,dip direction and friction angle of the dominant discontinuity set, and the stability condition is assessed with a factor of safety based on the classical frictional joint constitutive model. A Box-Behnken design(BBD) approach is then adopted to create the surface response function as a second order polynomial for the factor of safety. To do so, fifteen FLAC3 D models are generated in accordance with the BBD.Based on this, 10,000 simulations of different slope realizations are carried out using Monte-Carlo simulation technique, and the probability of unsatisfactory of performance of the rock slope is assessed. It is shown that the probabilistic approach provides more insight and confidence in the stability condition of the rock slope, both under dry and steady state heavy rainfall conditions. A discussion is presented on the significance of accepting lower safety factors when heavy rainfall conditions are encountered.     

Application of three-dimensional discrete element face-to-face contact model with fissure water pressure to stability analysis of landslide in Panluo iron mine

1 Introduction Rock slopes usually contain many jointed surfaces such as joint fissure. When subject to water seepage, the jointed surfaces will induce many geologic disasters such as land- slide and mudflow, and these will do great loss to the national economic development. Therefore, it is very important to deeply understand the mechanism of these disasters. Site observations and analysis on the landslide show that water is one of the key factors to induce landslide[1―8]. All methods calcu…     

Probabilistic approach for open pit bench slope stability analysis——A mine case study

The geotechnical slope design of an open pit wall starts at the bench scale configuration. At this scale, the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a result, structurally-controlled failures(e.g. planar, wedge or toppling) are most likely to occur. The probabilistic approach offers a major advantage over the traditional deterministic method in that it accounts for the different degrees of variability and uncertainty often encountered in rock properties. This paper presents a bench slope stability assessment for an open pit mine in Peru using a probabilistic-based approach by coupling a kinematic analysis based on stereographic projection techniques followed by a kinetic analysis by means of the limit equilibrium method. Finally, these two probabilities are combined to provide an overall measure of the probability of failure(PoF) of the bench slope system. The case study is characterized by significant scatter in the geometrical and mechanical properties of the joints.Extensive surface mapping was conducted at 36 different sites following the ISRM suggested procedures.Several direct shear tests were carried out. It is shown that by combining field and laboratory measurements and engineering judgment, the probability density functions(PDF) of the discontinuity parameters can be obtained. These are then used in a Monte Carlo simulation process to compute both kinematic and kinetic probabilities of failure. The overall probability of failure aims to provide the design engineer with a tool to critically evaluate the bench performance from a geotechnical risk perspective and to provide a basis for future bench design optimization.     

Influence of canopy ratio of powered roof support on longwall working stability——A case study

The case study describes longwall coal seam A in a hard coal mine, where longwall coal face stability loss and periodic roof fall occurrences had been registered. The authors have attempted to explain the situation based on in-situ measurements and observations of the longwall working as well as numerical simulation. The calculations included several parameters, such as powered roof support geometry in the form of the canopy ratio, which is a factor that influences load distribution along the canopy.Numerical simulations were realized based on a rock mass model representing realistic mining and geological conditions at a depth of 600 m below surface for coal seam A. Numerical model assumptions are described, while the obtained results were compared with the in-situ measurements. The conclusions drawn from this work can complement engineering knowledge utilized at the stage of powered roof support construction and selection in order to improve both personnel safety and longwall working stability,and to achieve better extraction.     

Response of an old landslide to reservoir filling: A case history

1 Introduction It is generally believed that reservoir slope instability is mainly caused by unfavorable hydrodynamic evolution in the bank due to reservoir filling and/or operation. Many cases of instability were reported both in China and abroad, causing life fatalities and economic losses, and even leading to project abandonment[1-5]. Riemer[5] reviewed 60 published case histories and indicated that 85% of slide events happened during con- struction and/or filling period, or within 2 years …     

Radon bearing water protection in underground uranium mining——A case study

High pressure, radon bearing water has been identified as one of the most critical challenges in mining the high-grade uranium deposit at the Mc Arthur River Operation, Cameco Corporation. The ore deposits are located between 490 and 640 m below the surface and surrounded by water bearing Athabasca sandstone, a graphitic P2 fault zone, and highly altered ground. This paper introduces the inflow risk management program at Mc Arthur River Operation, which includes various hydrogeological challenges and the corresponding strategies applied, such as risk-based probe and grout programs(geological, hydrogeological, and geotechnical), ground freezing programs, and comprehensive ground control programs. These programs have been developed, tested, and proven successful over years of mining practices. Working with this world class deposit of high risk and low tolerance, it is believed that these experiences might be beneficial to other mining operations with similar hydrogeological characteristics.     

Improved response surface method and its application in stability reliability degree analysis of tunnel surrounding rock

An approach of limit state equation for surrounding rock was put forward based on deformation criterion.A method of symmetrical sampling of basic random variables adopted by classical response surface method was mended, and peak value and deflection degree of basic random variables distribution curve were took into account in the mended sampling method. A calculation way of probability moment, based on mended Rosenbluth method, suitable for non-explicit performance function was put forward. The first, second, third and fourth order moments of functional function value were calculated by mended Rosenbluth method through the first, second, third and fourth order moments of basic random variable. A probability density the function(PDF) of functional function was deduced through its first, second, third and fourth moments, the PDF in the new method took the place of the method of quadratic polynomial to approximate real functional function and reliability probability was calculated through integral by the PDF for random variable of functional function value in the new method. The result shows that the improved response surface method can adapt to various statistic distribution types of basic random variables, its calculation process is legible and need not iterative circulation. In addition, a stability probability of surrounding rock for a tunnel was calculated by the improved method, whose workload is only 30% of classical method and its accuracy is comparative.     

Coal seam drainage enhancement using borehole presplitting basting technology——A case study in Huainan

Xinji No. 2 underground coal mine extracts the coal seams #4 and #5. These two seams are highly gassy and gas drainage is required to control mine gas emission and reduce outburst risk. Because the seam permeability coefficient is very low and around 0.1 m~2/(MPa~2·d), a number of technologies have been trialled to enhance the seam permeability prior to gas drainage. Of these technologies trialled, the deep borehole presplitting blasting technology has been proven to be quite effective in increasing permeability. In Xinji No. 2 mine it doubled or sometimes tripled gas drainage volume. This paper describes the technology, its application in the enhancement of seam permeability in Xinji No. 2 coal mine, and its effect on gas drainage performance.     

Numerical simulation and disaster prevention for catastrophic fire airflow of main air-intake belt roadway in coal mine—A case study

Coal mine belt fire develops very rapidly and is difficult to control. If not suppressed quickly, a belt fire could easily lead to airflow disorder and undermine the ventilation system. However, belt fire can be prevented effectively by establishing fire airflow control system. In this work, the 5th belt roadway of Kongzhuang coal mine was taken as the object of investigation, where geometrical models of this roadway were established firstly. Then, based on mathematical model of fire smoke flow, the CO volume fraction, smoke density distribution, air temperature and pollutant velocity vector in the roadway before and after taking airflow control measures were simulated by using Fluent software. It can be known from the simulation that with the normal ventilation status in 5th belt roadway, the countercurrent of smoke does not happen when a fire occurs; the roadway's section is almost filled with CO at 10 m downstream from the fire source, and with air velocity getting stable gradually, the CO concentration reaches about 15 %. After taking airflow control measures, the effect range of temperature field which are harmful to the miners decreases from 69 m to 30 m; and the distance of the roadway fully filled with CO is 5 m farther than that before taking measures. Finally, according to the numerical simulation results and the actual condition of the belt roadway, the warning and automatic remote airflow control system with short-circuit method for the 5th belt roadway was designed to guarantee the safety production.     

Experimental study on pore pressure in rock-soil slope during reservoir water level fluctuation

1 Introduction The effect of seepage flow is a key problem in the investigation on the landslide fail- ure. Water in landslide comes mainly from the infiltration of rainwater and seepage flow of ground water. Rivers and reservoirs are the dominant sources of ground water in landslide. The infiltration of water will cause variations of the ground water level in landslides, which sometimes play a key role in the landslide stability. In particular, the fluctuation of water level varies remarkabl…     

考虑降雨入渗的某矿区滑坡数值模拟分析

矿区坡体土质粘粒较少,在二次翻采、随意堆弃工况下,极易造成滑坡区土质疏松、加大土体的孔隙率。根据矿区滑坡坡体的工程地质及工况特点,考虑土体内应力场与渗流场之间的流—固耦合作用,采用有限元法,对比分析了某矿区滑坡体的边坡在降雨前、后的边坡安全系数.数值分析表明,考虑降雨入渗的情况下边坡安全系数明显下降.     

PC机集群系统在电力系统暂态稳定分析中的应用

从网络分割的角度出发,采用了一种基于支路分割的并行算法,以分割支路两端的电压为交接变量,将分割支路两端的节点看作有注入电流的节点,通过迭代最终实现并行计算。继而以MPICH.NT.1.2.5作为操作平台,利用传递函数库实现并行通讯。最后通过IEEE39节点系统对该算法进行了测试,验证了该算法的正确性,并且通过与传统算法的比较得到了令人满意的并行加速比。     

Experimental and discrete element numerical analysis of side slope instability induced by fissure water underlying impervious bed

1 Introduction The in situ observations and analysis on the landslide events indicate that water is one of the key factors which induce landslide of the mountain mass[1―8]. The mechanism offissure water inducing landslide can be generalized into three aspects: (1) the softening influence of water weakens the strength of materials on the slip surface[9―11]; (2) the cleft water pressure towards the slide slope free face increases sliding force[12―15]; (3) water pressure on the slip surface lo…     

中国气候变化敏感区气温变化对比

近50 a来全球气候变化已经是当今自然科学重大课题之一,中国的区域响应也日渐引人关注.依据黑龙江、新疆、西藏3省区93个国家基准或基本气象站1961—2008年的日气温数据,就年均气温及四季气温变化过程和特征进行了对比分析.3省区增温幅度分别为1.71,1.20,1.15℃,且线性趋势明显;增温过程方面,黑龙江和西藏均为持续增温,而新疆增温、降温过程动荡大;季节对比可知,虽然黑龙江以冬春、新疆和西藏以秋冬增温最强,但冬季的贡献率都最为显著,分别为38.35%,38.73%和36.75%.