水平岩层软弱基座危岩体演化过程研究

以重庆市甄子岩29号危岩体为研究对象，基于现场调查和分析解剖，建立UDEC离散元数值计算模型，对其演化变形过程进行模拟分析。研究表明，在巨大的自重作用下，由于基座岩体岩质软，岩体较破碎，且基座外侧为直立的陡崖，具有完整的临空面，从而使基座岩体易发生压缩流变及剪切流变，进而使危岩体存在滑移垮塌的危险。     

高频次微小地震下顺倾软硬互层边坡动力稳定性研究

三峡库区(TGR)自蓄水以来微震活动加剧、强度增大,频发微震会对库区边坡产生一定影响。采用振动台模型试验和UDEC数值模拟方法,对库区顺倾软硬互层边坡在不断微、小地震作用下的破坏失稳演化过程及动力稳定性进行了研究。研究成果如下:在不断地震作用后,边坡自振频率下降、阻尼比上升,自振频率下降的速度随加载次数和加载幅值的增加而增大;在不同加载阶段,边坡坡面PGA放大系数不断降低,动力响应呈现减弱趋势;弱层成为顺倾软硬互层边坡变形破坏的优势区域;边坡的破坏失稳演化过程为分段式的滑移破坏过程,上部软、硬层滑落后,剩余滑体沿着由上部弱层剪切裂缝、中部硬层次级节理拉裂缝和下部弱层剪切裂缝贯通形成的滑移面滑移破坏;UDEC数值模拟表明顺倾软硬互层边坡的累积永久位移随微震作用次数的增加而增加,稳定性系数则呈现递减趋势。研究成果对库区滑坡形成机制的认识和减灾、防灾有一定的价值。     

爆破荷载作用下黄麦岭磷矿岩质边坡动态响应的UDEC模拟研究

运用二维离散单元程序UDEC，模拟了爆破荷载作用下黄麦岭磷矿采场岩质边坡的动态响应，并将计算结果与现场监测结果进行了比较。结果表明，两者吻合得较好。因此，UDEC应用于模拟爆破荷载作用下边坡的动态响应研究是适合的。     

频发微震下上覆软弱岩体边坡动力稳定及失稳模式

水库蓄水诱发的高频次微小地震对库岸边坡稳定性存在一定影响。采用振动台物理模型试验,结合UDEC离散元分析方法,以三峡库区杉树槽滑坡为原型,研究了频发微震作用下典型上覆软弱岩体边坡的累计损伤过程、动力响应特征及破坏模式。结果表明：在频发微震作用下,模型边坡自振频率不断降低,阻尼比不断升高,完整性降低;坡体加速度响应在初始阶段和微震阶段体现出“高程效应”和“趋表效应”,而在小震加载后,坡体动力响应与上述特征出现偏离;在反复微震下,坡体的破坏演化过程可概括为“次级节理发育→次级节理扩展→上部岩体破碎→后缘裂隙扩张→滑面贯通→边坡失稳破坏”阶段;离散元数值分析结果表明,上覆软弱岩体边坡在频发微震下的变形主要发生于岩层分界面以上,后缘裂隙以下的上部岩体,随着地震次数的增加,其永久位移不断增大,边坡稳定性系数不断降低,边坡破坏特征与振动台试验结果相吻合。     

简易物料提升系统在集中煤仓维修中的应用

介绍了大隆煤矿集中煤仓维修概况,阐述了施工维修前的准备工作、具体维修方法及流程,通过南一集中煤仓自创简易物料提升系统,有效解决倾斜煤仓下放、提升物料的安全性,减少作业人员对倾斜煤仓下放、提升物料的作业强度和施工的不利危险因素,达到充分利用设备工具、增加工作效率、降低人员劳动强度的目的,有一定的借鉴意义。     

Optimum model extent for numerical simulation of tunnel inflow in fractured rock

The objective of this study is the introduction of an optimum model extent in discontinuous rock masses for tunnel inflow assessment using numerical models. Tunnel groundwater inflow is an important problem in tunneling, and numerical simulation is widely used for estimating the amount of tunnel inflow. An adequate size of the model domain is of very high importance when using such models. On the one hand, if the tunnel boundary is too close to the outer model boundary, the simulated inflow rate into the tunnel is significantly overestimated (which will be shown in the present study). On the other hand, if the model domain is very large, models may become “unhandy”, and simulations become very expensive with respect to computer memory and CPU. In this technical note, an approach is presented that derives an optimum model extent for numerical simulation of tunnel inflow in fractured rock. The approach uses the two-dimensional universal distinct element code (UDEC). The impact of different model parameters, such as tunnel radius, groundwater level, joint spacing, joint dip/dip direction and joint aperture on the optimum model extent has been evaluated. Based on the results, an optimum model extent chart is presented that allows modelers a quick determination of the optimum model extent as a function of the most significant parameters, which are the tunnel depth under the groundwater level, tunnel radius and joint spacing.     

Stress arch bunch and its formation mechanism in blocky stratified rock masses

Stress arch is a common phenomenon occurring in continuous materials and has also been proved to have great influences on the self-stabilization of soils or rock masses after excavation.In this paper,based on UDEC simulation,stress redistribution after excavation is investigated for a kind of special discontinuous material,i.e.blocky stratified rock mass.A layered stress arch system is observed with each stress arch lying over another.This special phenomenon is defined herein as "stress arch bunch".Effects of dip angle of bedding plane,lateral pressure and joint offset on this stress arch bunch are studied.Its formation mechanism is also discussed based on voussoir beam theory.     

Comparison of empirical and numerical methods in tunnel stability analysis

The stability of a tunnel can be evaluated using mathematical solutions, empirical methods, or numerical modelling. Mathematical solutions are precise methods; however the need to conduct mathematical calculations usually decreases the user's desire to use this method. Empirical methods are based on the experience gathered by researchers in various parts of the world whereas numerical modelling utilises computing power and, using various modelling techniques, can be a precise way of solving very complex problems. In this method the environment and the geometry can be set by the user. This method allows the user to conduct sensitivity analysis. In this article, empirical methods and numerical modelling using UDEC software were used to conduct a stability analysis of the access tunnel at the Shahriar dam crest, which was one of the most important tunnels of this project. In addition, numerical modelling was used to predict the stresses and deformations around the perimeter of the tunnel, and select the most suitable ground support system. The results obtained from both methods were compared for selection of the best suited support system. The results indicated that the empirical methods presented similar results to the results of numerical modelling at the first stages of tunnel design in jointed rocks. Therefore, in the absence of sufficient information for numerical analysis, the results of the empirical method can be used for this project.     

采动作用下含深大岩溶结构面坡体裂隙扩展及变形破坏规律

中国西南高陡岩溶山区崩滑灾害频发,长期地下采矿活动是该区域崩滑灾害的重要诱因之一。采动作用下,坡体后缘深大结构面扩展演化控制着高陡岩溶坡体稳定性和失稳破坏模式。在野外地质调查基础上,结合室内物理模型试验和离散元数值模拟,揭示了地下开采扰动下覆岩裂隙扩展演化规律,阐明了深大结构面对边坡稳定性的控制作用,讨论了坡体变形的破坏模式。结果表明：地下开采扰动对斜坡体稳定性的影响主要表现在地下采动卸荷引起覆岩应力重分布、山体变形诱使裂隙扩展;地下采空后,斜坡体在二维剖面上形成类似“悬臂梁结构”,坡体原有深大结构面控制坡体稳定性;下行开采条件下,采空范围在断层之前,山体高度较小,在自重作用下“悬臂梁结构”岩层向断层及采空区方向协同变形,不会产生大量离层裂隙,煤层顶板仅发生断裂坍塌并充填采空区,采空至断层后,左侧山体已发生塌落,山体应力重分布,覆岩在自重作用下形成大量张拉裂隙,直接顶塌落高度与裂隙带高度也随采空区范围增加而增加。其变形破坏演化过程可概化为：地下开采卸荷–应力重分布→覆岩断裂下沉–裂隙扩展→坡体裂隙贯通–悬臂破坏→坡中变形挤出–岩桥剪断→坡体整体失稳破坏。     

自由面对滚刀破岩机制影响的数值模拟研究

为了研究自由面对滚刀破岩机理的影响,运用UDEC方法建立了滚刀贯切岩石的二维数值系列模型,对TBM滚刀破岩过程进行了仿真。分析表明：在合理的刀间距和贯人度情况下,破碎坑自由面的存在使裂纹扩展能耗降低,裂纹密度增大,起裂方式增多,容易实现体积破碎,提高滚刀破岩效率。