A discontinuum-based model to simulate compressive and tensile failure in sedimentary rock

The study presented in this paper discusses a discontinuum-based model for investigating strength and failure in sedimentary rocks.The model has been implemented by UDEC to incorporate an innovative orthotropic cohesive constitutive law for contact.To reach this purpose,a user-defned model has been established by creating dynamic link libraries(DLLs)and attaching them into the code.The model reproduces rock material by a dense collection of irregular-sized deformable particles interacting at their cohesive boundaries which are viewed as flexible contacts whose stress-displacement law is assumed to control the fracture and the fragmentation behaviours of the material.The model has been applied to a sandstone.The individual and interactional effects of the microstructural parameters on the material compressive and tensile failure responses have been examined.In addition,the paper presents a new methodical calibration procedure to ft the modelling microparameters.It is shown that the model can successfully reproduce the rock mechanical behaviour quantitatively and qualitatively.The study also shows how discontinuum-based modelling can be used to characterize the relation between the microstructural parameters and the macro-scale properties of a material.     

电爆网路在高电磁场地区岩石爆破中的应用

电爆网路目前仍然在工程中被采用。结合爆破工程施工规模和现场布孔情况,必须对网路电阻进行严格的设计和计算,并进行实测,进而确定安全有效的起爆网路。计算和施工结果表明,在高电磁场区域,根据每个工作面爆破规模大小,一般考虑排间并联,排内串联。当爆破规模达到2万方以上、工作面为2~3个时,计算要使通过每个电雷管的电流不小于2.5mA,可以采用2组并联、组内串联方式起爆。同时,工作面杂散电流应不大于30mA。     

岩石力学数值模拟力学参数的确定与验证

依据赵庄煤矿地质勘探报告,结合不同岩层性质,采用岩石质量评价法,确定了各岩层合理的节理间距与力学参数。依据合理的岩石、节理力学参数,对3304工作面采动岩层数值模拟,将模拟结果中冒落带、裂隙带的高度与经验公式计算、现场高位钻孔考察分析结果比较,模拟得出的覆岩冒落规律接近于工程实际,验证了节理间距与力学参数的合理性。     

Slope stability analysis of Balia Nala landslide,Kumaun Lesser Himalaya,Nainital, Uttarakhand,India

Balia Nala is the outlet of the Nainital lake, flowing towards southeast direction. Presence of Nainital habitation at its right bank has high socio-economic importance. This study presents the stability analysis of a ravine/valley along Balia Nala. Variegated slates(lower Krol and upper Blaini formations) are the main rock types, wherever the outcrop does exist and rest of the area is covered by slope wash and river borne materials. Three sets of joints are presented in the area, but 4 sets of joints also exist at some locations. Nainital lake fault intersected by Manora fault from southwest direction passes through eastern side of the study area, and some small faults, which are sub-branches of Nainital lake fault, are observed(with 10 m offset) and promote the landslide in the area. This study shows that different kinds of discontinuities(joints, faults and shear zones) and rapid down cutting by the stream due to neotectonic activity affect the stability of the slope. The fragile lithology and deep V-shaped valley further accelerate the mass movement in the study area. In addition, rock mass rating(RMR), factor of safety(FOS) and graphical analysis of the joints indicate the study area as landslide-prone zone. This study will be helpful in not only reducing the risk on life of people, but also in assisting the ongoing civil work in the study area.     

Experimental investigation on sealing efficiency of chemical grouting in rock fracture with flowing water

This paper presents an experimental investigation of the main factors that influence the sealing efficiency of chemical grouting in a permeated fracture replica. Chemical grouting has been widely used to control groundwater inrush in underground mining. However, the relationship between the sealing efficiency of grouting and its influencing factors is one of the many critical issues that still remain unsolved. The four factors tested in the orthogonal experiment include the fracture aperture width, initial water flow speed, gel time, and grout take. The sealing efficiency is evaluated and graded by the reduction of water drainage through the fracture after grouting. The experimental results of the orthogonal arrays show that two most influencing factors on sealing efficiency are the initial water flow speed and the aperture width, where the former has a higher impact than the latter. In a comparison with the two other factors, it is found that the grout take and gel time have less influence. The patterns of grout propagation are classified into four types: (1) total sealing off; (2) partial sealing off with erosion along boundaries; (3) partial sealing off with internal erosion; and (4) total erosion. The interaction between the injected grout and flowing water slows down the water flow and the grout starts to solidify at a downstream location where the retention time for grout is longer than its gel time.     

The impact of the physical model selection and rock mass stratification on the results of numerical calculations of the state of rock mass deformation around the roadways

At present, the basic methods used for designing and evaluating the stability of mine workings are numerical models. The finite element method is the most popular method for engineering purposes. However successful calculations depend not only on the proper selection of geomechanical properties of rocks but mainly on the proper selection of a physical model describing the behavior of the rock mass and a selection of the correct failure criterion. The best way of verifying results of the calculations is to carry out investigation in the field, then.This article shows how the choice of a numerical model affects the size of the calculated damage zone around the working. To that end, numerical calculations considering elastic and elastic–plastic models were performed for six roadways. The rock mass was further differentiated in terms of its stratification and approach to mechanical properties of the rock mass. The results of these calculations were compared with measurements of mine convergence and the damage zone range in the roof. Such measurements were carried out at hard coal mine roadways.     

江苏溧水火山岩盆地观山旋回岩石学特征

本文着重描述厂江苏溧水中生代火山岩盆地观山旋回岩石的岩石学、岩石化学和稀土元素等方面的特征.观山旋回火山岩普遍为高钾富碱的中偏碱性岩类;稀土元素特征为轻稀土富集,Eu 弱负异常,与大陆裂谷碱性玄武岩的稀土特征明显相似.最后就本区火山岩的岩浆来源作了初步讨论.     

岩石可钻性能量法现场实验研究

本文介绍了岩石可钻性能量法在油田现场实验研究的成果：确定其可钻性指标Ｋｎ对地层的适用范围；证明Ｋｎ指标比其他可钻性指标能更容易、更好地反映出井下实际地层可钻性变化情况；用Ｋｎ指标预测钻速与实际钻速接近．     

节理岩体的有限元分析

本文由节理和岩块体变形迭加的方法推导出节理岩体的应力—应变关系式,并分析了各种节理和岩块体破坏的组合形式及其变形状态,因而能较准确地反映节理岩体的破坏机理。     

岩石声发射特性的研究

本课题自1982年7月开始,至1986年7月结束。其中分为三个阶段:第一个阶段是准备阶段,对国内外的情况进行调研,建立本课题研究内容的测试系统,添置必须的仪器、换能器、刚性试验装置,进行测试系统的调试;第二阶段是室内实验,其目的在于研究应力应变全程曲线各阶段内的岩石声发射规律,用岩石声发射的多参数、多频率窗口变化规律探讨岩石试件破坏的机制,寻找岩体失稳最为可靠的参数,为现场岩体失稳预报建立坚实的理论基础;第三阶段是在牟定铜矿井下采场进行现场监测,其目的在于验证室内实验所获得的岩石声发射规律,并用这些规律去指导围岩稳定性监测,最后监测记录到了两次片帮事故。