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

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.     

广东大沟谷钠长石岩金矿床地质特征及成因

大沟谷金矿赋矿岩石为钠长石岩，围岩为震旦纪区域变质岩，矿体与围岩斜交，并被北西向次级高角度韧性断裂控制。矿体金平均品位为４．１４～７．２０ｇ／ｔ，金含量与钠长石岩的蚀变强度及所受构造应力强度成正相关．矿床岩石化学、稀土元素、流体包裹体成分、稳定同位素地球化学等特征表明，其属中高温热液交代充填型金矿床。     

河流涌潮区段粉砂地基抛石防冲保护施工方法和防冲效果分析

通过绍兴县口门治江中片围涂工程为例,详细阐述了防冲保护(抛石护底法)的施工方法和施工原理.结合工程施工过程中的实际情况,对实测数据进行分析,对抛石护底的防冲效果进行评价,同时指出了抛石护底的实施方法、实施要点和实施效果.综合论述了河流涌潮区段粉砂地基抛石护底防冲保护方案的可行性、经济性和适用性.     

塔里木盆地塔中地区奥陶系油气成藏主控因素及勘探选区

通过对塔中地区钻遇奥陶系的60余口探井油气成藏及失利原因的综合分析,提出该区奥陶系油气成藏的主控因素为:①中、上奥陶统(相当于黑土凹组—萨尔干组的层位)主力烃源岩控制了塔中地区的油气分布,其主要分布于塔中凸起北部斜坡区;②4套碳酸盐岩储层(志留纪—泥盆纪古潜山岩溶储层、中奥陶世晚期—晚奥陶世早期古潜山岩溶储层、上奥陶统良里塔格组棚缘礁滩体埋藏溶蚀储层及下奥陶统内幕白云岩储层)的分布及其非均质性对成岩—岩性圈闭油气藏的形成起到了至关重要的作用;③二叠纪—早三叠世是塔中地区现今工业性油藏的主要成藏期;④圈闭及其封盖—保存条件决定了油气藏的规模。针对塔中地区奥陶系油气勘探选区及勘探步骤,提出具体的勘探工作可分3个层次进行:①近期主攻塔中I号断裂带南侧良里塔格组棚缘礁滩体成岩圈闭特大型岩性油气藏,兼探中央断垒带东段(塔中401—塔中9井区)下奥陶统古潜山岩溶储层油气藏;②对塔中10号构造带及其与中央断垒带之间的中奥陶世晚期—晚奥陶世早期形成的下奥陶统鹰山组中上部古潜山岩溶储层油气藏及塔中1—塔中7—塔中48井区下奥陶统古潜山岩溶储层油气藏进行勘探;③在存在沟通油源断裂的前提下,对满加尔凹陷区上奥陶统浊积砂岩—陆棚—三角洲—滨岸潮坪砂岩的构造及岩性圈闭油气藏进行勘探。     

Kaiser Effect in Rock Salt

Using the results of experiments with rock salt samples under various loading regimes as an example, the regularities of the Kaiser effect formation and manifestation in rocks with plastic properties are investigated.     

Changes in Properties of Rock Massifs Due to Underground Nuclear Explosions

Mechanical characteristics of rock massifs and constituent rocks in the zones of influence of underground nuclear explosions are experimentally determined. Zones with a different postexplosion structure of the rock massif and different properties of rocks are identified.     

Half tunnels along hill roads of Himalaya—an innovative approach

‘Half tunnels,’ which are excavated as overhangs within steep slopes of hard rocks, have an advantage over conventional full tunnels or open excavations in that they involve less cost and time. However, due to a lack of interest and their uncommon occurrence, the design and analysis of half tunnels have remained by and large unexplored. In the present paper, an effort has been made to study some of the half tunnels in the Middle and the Higher Himalaya in India. In addition to studying the geology of half tunnels, rock mass properties pertaining to Q and RMR for the rocks exposed around the half tunnel have been evaluated. The Markland test has been carried out to assess the probability of plane or wedge failures along the slopes in the half tunnel area. The results obtained have been again confirmed by analyzing the data with the help of a computer program . Both analyses suggest that the wedges are stable and that all the half tunnels analyzed are safe. Finite element analyses for different slopes and spans of half tunnels have been carried out to study the distribution of stresses around half tunnels. The range of maximum tensile stress concentration in the roof of half tunnels for different slopes is suggested.     

银额盆地查干凹陷基本生油条件研究

从有机地球化学方面深入研究了银根-额济纳旗盆地查干凹陷的基本石油地质条件。查干凹陷下白垩统沉积时为一箕状断陷,沉积地层和烃源岩厚度变化大,主要烃源岩发育于下白垩统巴音戈壁组和苏红图组下段,厚约0～2400m。目前烃源岩有机碳含量为0.15%～2.66%,热解生油潜量为0.07～10.74mg/g,氯仿沥青"A"含量多数在0.022‰～3.757‰,总烃含量为0.049‰～2.527‰。有机质丰度变化大,但可溶有机质含量相对较高。有机质主要由无定型草本植物降解和藻类组成(占60%～80%),其中II1型有机质占50%以上,推测原始有机质类型较好。该凹陷地热梯度较高,目前烃源岩镜质组反射率在0.8%～2.0%,处于成熟生油-湿气阶段,饱和烃色谱和色质参数也表明烃源岩已成熟。TTI计算表明其主要烃源岩主要生油期为晚白垩世。综合分析认为下白垩统烃源岩属较好烃源岩,具有一定的生油气潜力。图5表3参5(陈建平摘)     

辽西建平地区太古宙建平群小塔子沟组变质岩地质特征

辽西地区太古宙变质杂岩在建平一带分布最广泛，特征最明显，代表性最强，是一套片麻岩夹磁铁石英岩的变质岩系。经岩石学、地球化学研究表明，原来建立的建平群小塔子沟组变质岩，是由变质表壳岩和变质深成岩组成，以变质深成岩为主，变质表壳岩以包体形式漂浮与变质深成岩之中。变质表壳岩的斜长角闪岩、基性麻粒岩和超铁镁质岩为基性一超基性火山岩，磁铁石英岩成因与基性火山岩和基性火山沉积岩有亲缘关系。叶柏寿片麻岩和斜长片麻岩、二长片麻岩为侵入形成的闪长岩、英云闪长岩和二长花岗岩。     

小浪底水利枢纽左坝肩4~#排水洞渗漏问题分析

小浪底水利枢纽左坝肩4#排水洞是地下发电厂房上游的主要排水帷幕,通过对其排水量长期观测资料与渗压计监测资料以及库水位之间的线性特征进行了综合分析,合理解释了4#排水洞的水量变化与渗漏来源和途径之间的关系,确定了洞水遵循未饱和岩体渗水规律,水量主要来自绕坝渗漏,初步判定了库水渗漏点位置.为绕坝渗漏治理方案提供了切实可靠的依据.