正交各向异性岩体中地下洞室稳定的粘弹-粘塑性三维有限元分析

建立了一种正交各向异性岩体的粘弹－粘塑性模型，推导和描述了相应的数值计算表达式和有限元分析的步骤，并使用所编制的三维有限元程序，以在层状岩体（横观各向同性介质）中的地下洞室开挖为算例，考察了围岩的流变动态，得出了几点结论。     

浅析山区高等级公路中的边坡工程岩体

随着山区高等级公路建设的飞速发展，各类边坡工程岩体问题也日益增多。从卸荷岩体力学的基本观点入手，探讨了边坡工程岩体的变形破坏特性、稳定性评价方法以及开挖设计理论。研究表明，边坡工程岩体的变形破坏特性完全符合卸荷岩体力学行为，不同于常规的加载岩体行为；边坡工程岩体的稳定性分析计算中必须重视水力学因素和卸荷作用的影响，并得到了有意义的表达式；边坡工程岩体的开挖设计应在充分认识其工程力学性状的基础上，针对边坡岩体地质特性，结合已有各类稳定边坡的资料，进行既经济又可靠的优化设计。     

不同的层状岩体抗剪强度表达式计算效果的有限元分析

为考察不同的各向异性抗剪强度表达式对于数值计算结果的影响,以一个假定的位于层状岩体中的矩形地下洞室为背景,分别使用笔者和Pietruszczak各自提出的材料摩擦系数和黏聚力随方向变化的公式,进行3种工况的弹塑性二维有限元模拟,对比了围岩中的应力、位移及塑性区。结果显示,笔者提出的经验表达式与和相应的Pietruszczak一阶表达式在计算中的精度基本相当,而与Pietruszczak的二阶表达式相比有较明显的差别。     

攀西地区红格层状岩体的地球化学特征

红格岩体赋存有大型钒钛磁铁矿床，在橄辉岩相带和辉石岩相带底部有铂族元素（PEG）的矿化，是攀西层状岩体中重要的岩体之一，系统分析了红格层状岩体不同岩相带的微量元素和稀土元素特征，探讨了岩浆的结晶分异演化过程，提出岩体主体上是由一个岩浆房经正常的结晶分异形成的，底层的硫化物富集带和中上层位的钒钛磁铁矿是岩浆结晶分异产生的堆积相，并非是岩浆多次脉动式补给的结果。     

控制岩体活动的地质因素分析

本文对控制岩体活动的地质因素—岩性、岩体结构、结构面、地应力和水文地质条件等进行了分析。岩性、岩体结构是产生岩体活动的内因。本文将岩体结构划分为六种类型,即整体结构、块状结构、层状结构、碎裂结构、镶嵌结构和散体结构。并对控制岩体稳定性的结构面进行了研究和分类,指出不同结构面对岩体活动的具体影响。通过各种控制岩体活动的地质因素分析,掌握岩体活动规律,对予防灾害性岩体活动,防患于未然有实际意义。     

论岩体表征单元体积REV岩体力学参数取值的一个基本问题

本文论述了岩体力学性质的尺寸效应,提出了与岩体弹性参数相应的表征单元体REV的力学描述,根据中心极限定理推导了估算裂隙岩体REV 的数学表达式。研究表明,岩体表征单元体的大小是岩体力学性质尺寸效应的客观反映。本研究成果为合理选取岩体力学参数提供了一条新途径。     

三维应力作用下岩体单个裂隙的渗流特性分析

天然岩体中存在着大量的孔隙和裂隙,这些缺陷不仅改变了岩体的力学性质,也严重影响了岩体的渗流特性。在对现有裂隙岩体渗流特性研究成果进行分析的基础上,讨论了岩体单个裂隙的力学性质和渗流对单个裂隙岩体产生的力学作用,研究了岩体单裂隙渗透系数与岩体三维应力的关系,考虑了裂隙粗糙度对渗流的影响以及不同方向应力对渗透性影响的差异,分析了单个裂隙岩体在三向应力作用下的渗流特征,得出了裂隙所受三维应力与渗透系数关系式,认为垂直于裂隙面的应力对岩体渗透性起主导作用,岩体渗透系数随垂直裂隙面应力的增加而迅速减小。通过与渗流规律试验结果对比分析,证明了所得单个裂隙岩体渗透系数表达式的正确性。     

巴楚瓦吉里塔格火成杂岩体岩石学研究

根据地质学、岩石学、地球化学研究，确定瓦吉里塔克火成杂岩体由3部分组成；层状岩体、角砾岩岩筒和晚期脉岩，其形成的年龄分别为357．9－306Ma、252.7Ma、231.3Ma。证实层状岩体为岩浆房原地分离结晶作用形成，具有碱性岩浆的肯尼迪演化趋势并发育液态不混溶作用，最终形成具有实际矿物霞石的过碱性岩。确定角砾岩筒并非金伯质，实为角砾云母橄辉岩。确定晚期脉岩与角砾云母橄辉岩为同期岩浆活动的产物，而且均发生在层状岩体固结之后。此外，根据它们富含H2O和富集大离子亲石元素的特点推测，该岩浆来源于富含流体相且不同于层状岩体的源区。     

深埋隧道层状围岩变形特征分析

层状岩体在地下工程中经常遇到的,它具有明显的各向异性力学性质。结合共和隧道现场监测和数值模拟相结合的方法对层状岩体的破坏特征进行了分析,研究结果表明：围岩的变形位移、破坏区都主要集中隧道拱顶右侧,即靠河侧大于靠山侧。隧道围岩变形破坏区不在最大主应力方向上,而是在岩体层理垂直方向。层状岩体中洞室变形破坏特征除了因地形产生的偏压影响外,更重要的是受地层结构特征的影响,即与层状岩体的力学性质极大相关,其结果可为指导隧道的施工和设计提供有效依据。     

论岩体结构的表生改造

在我国西南、西北一些在建和拟建的大型水电枢纽工程区，大量的工程地质调查表明，这些地区浅层岩体的表生改造相当发育，它们对岩体的工程地质特性及斜坡岩体的稳定性有显著的影响．本文在现场地质调研的基础上，对一由花岗岩构成的坝区所产生的上述现象作了详细的研究，探讨了岩体结构表生改造的力学机制和典型鉴定特征，建立了相应的地质力学模型，并对表生改造对岩体工程地质特性的影响作了简要讨论．     

Maximum entropy and shear strain of shear zone

The principle of maximum entropy can be used to determine the shear strain in natural shear zones. When the margin of a shear zone is assumed, the principle leads to the truncated exponential distribution of the shear strain. Ifx is the distance remote from the shear zone center, which possesses the maximum shear strain, the shear strain (x) is given by

钙质砂抗剪强度特性的环剪试验

珊瑚礁沉积的钙质砂与石英砂的物理力学性质有较大差别。对取自南海岛礁的钙质砂进行了单次往返环剪试验以分析钙质砂的抗剪强度特性,试验中考虑了相对密实度和竖向应力对结果的影响,并与相同级配和试验条件下的石英砂进行对比分析。结果表明：钙质砂正向剪切时应力-位移曲线为软化型,具有明显的残余强度特性,而反向剪切时则表现为硬化型,正向和反向剪切强度基本一致;石英砂正向剪切和反向剪切均表现为软化型。钙质砂正向剪切和反向剪切残余强度与峰值强度的比值在0.75～0.93之间;石英砂正向剪切和反向剪切残余强度与对应峰值强度的比值在0.89～0.96之间。相同级配和试验条件下,钙质砂残余强度均大于石英砂,且强度比值基本保持在1.05～1.3之间。在100、200 kPa竖向荷载作用下,钙质砂0.5～2.0 mm的颗粒发生了破碎,破碎率分别为4%和6%。     

直剪剪切速率对钙质砂强度及变形特征的影响

为深入研究剪切速率对钙质砂强度和变形特征的影响,对钙质干砂进行不同剪切速率条件下的直剪试验。研究结果表明,随剪切速率从0.1 mm/min增至2.4 mm/min时钙质砂抗剪强度先减小后增大,其内摩擦角亦呈现出先减小后增大趋势,临界剪切速率为1.6 mm/min;低法向应力条件下钙质砂试样随剪切速率的增加更易于呈现剪胀现象,高法向应力条件下剪切速率从0.1 mm/min增长至1.6 mm/min时试样整体剪缩量逐渐减小;当剪切速率继续从1.6 mm/min增长至2.4 mm/min时试样最大剪缩量逐渐增加;不同法向应力水平条件下钙质砂加载速率效应的细观机制不同,较低应力水平条件下钙质砂加载速率效应主要由试样内部颗粒错动、换位、重新排列引起,在较高应力水平条件下钙质砂加载速率效应主要由颗粒破碎引起。     

Influence of shear speed and normal stress on the shear behavior and shear zone structure of granular materials in naturally drained ring shear tests

“Sliding Surface Liquefaction” is a process causing strength loss and consequent rapid motion and long runout of certain landslides. Using a new ring shear apparatus with a transparent shear-box and digital video camera system, shear-speed-controlled tests were conducted on mixed grains (mixture of three different sizes of sand and gravel) and mixed beads to study shear behavior and shear zone development process under the naturally drained condition in which pore pressure is allowed to dissipate through the opened upper drainage valve during shearing. Higher excess pore water pressure and lower minimum apparent friction were observed in the tests where grain crushing was more extensive under higher normal stress and higher shear speed. Along with the diffusion of silty water generated by grain crushing, smaller particles were transported upward and downward from the shear zone. Concentration of larger grains to the central and upper part of the shear zone was confirmed by means of visual observation together with grain size analysis of sliced samples from several layers after the test. On the other hand, smaller particles were accumulated mostly below the layer where larger grains were accumulated. The reason why larger grains were accumulated into the shear zone may be interpreted as follows: grains under shearing are also subjected to vertical movement, the penetration resistance of larger grains into a layer of moving particles is smaller than that into the static layer. Therefore, larger grains tend to move into the layer of moving grains. At the same time, smaller particles can drop into the pores of underlying larger grains downward due to gravity.     

Correlation of large displacement drained shear strength of landslide soils measured by direct shear and ring shear devices

Based on a laboratory study of drained direct shear tests of remoulded, pre-cut and polished specimens and drained ring shear tests of uncut and remoulded specimens of slip surface materials of five landslide soils, significant correlations of the mobilized shear strength parameters, cohesion (c, c _r) and internal friction angle (Φ, Φ_r), are proposed. The investigated soils consisted of the slip surface material belonging to tuffaceous clay, mudstone, loess and siltstone. Most of the previous studies on residual shear strength measured by reversal direct shear and ring shear devices have obtained significantly different results using the two devices, even when pre-cut and polished specimens were used in the direct shear device. In this study, the residual shear strength values of remoulded specimens measured by a ring shear device are shown to significantly correlate with the drained large displacement shear strength values of remoulded specimens, which were measured using pre-cut and polished specimens in a direct shear device. The correlation between the cohesion measured in the two shear devices is expressed by the linear relationship, $ {c_{\text{r}}} = 0.{7394}c - {6}.{6857} $ , while the correlation between the friction angle measured in the two devices is expressed by the linear relationship, $ {\Phi_{\text{r}}} = {1}.0{852}\Phi - {6}.0{247} $ . The proposed linear correlations for effective cohesion (c′) and effective friction angle (Φ′) have yielded significant coefficients of determination within an effective normal stress range of 30–150?kN/m².     

Influence of shear heating on microstructurally defined plate boundary shear zones

In plate-boundary scale ductile shear zones defined by microstructural weakening, shear heating may lead to a temperature increase over 5 m.y. of up to 80 °C just below the brittle ductile transition, up to 120 °C just below the Moho, and to thermal boundary zones tens of km wide on either side of the shear zone. Where rock strength is highest, shear zones are narrow (∼1 km), and thermal gradients within the shear zone itself are low, so there is no tendency for increased localization. Heating results in thermal weakening, but this is partly offset by grain growth related to the decrease in stress. In shear zones of the order of 10 km width, shear stress, strain rate, and hence heat generation are lower, and thermal gradients are insufficient to cause additional strain localization. Temperature increases in the mid-crust are of the order of 10 °C, insufficient to cause partial melting or an increase in metamorphic grade. In the upper mantle, shear zones may be 50 km or more wide, and the temperature increase is less than 20 °C in 5 m.y., but temperature differences between center and margin may enhance the strain rate at the center by up to 18%.     

重塑硅藻土抗剪强度的环剪试验研究

硅藻土是一种强结构性土,具有密度小、孔隙大、干燥土块吸水率高等特点。天然硅藻土的抗剪强度大,但在外界扰动或风化后,结构性强度丧失,易发生滑坡等斜坡变形破坏现象,因此,研究其在大变形下的力学性质很有必要。利用环剪仪可以研究土体在较大剪切位移条件下抗剪强度变化规律,对重塑硅藻土进行环剪试验研究,得到了不同竖向压力下的应力-位移曲线,认为重塑硅藻土为典型的应变软化型土;根据测试结果得到了重塑硅藻土的抗剪强度和残余强度,并从物质组成和微观结构特征方面对重塑硅藻土的力学性质进行了分析,为硅藻土滑坡的成因分析和灾害防治提供了依据。     

残积土抗剪强度的环剪试验研究

残积土风化剧烈,研究其大变形下的工程特性很有必要。利用环剪仪的试验特点,可以研究土体在较大剪切位移下抗剪强度的变化规律。通过对残积土残余和峰值强度的环剪试验测定和对试验数据的整理与对比分析,得到了含水率与残余强度指标之间的关系,证明大变形下残积土具有浸水软化的特性;从应变阈值角度分析了残积土应变软化的性质,不同剪切位移下的残积土具有不同的抗剪强度,所研究的残积土达到峰值强度对应的应变介于0.02～0.06之间,而到达基本稳定的残余强度所需要的应变介于0.06～0.20区域内。研究还发现,矿物成分不同直接影响到残积土的残余强度,是残积土不均匀性的内部因素     

Kinematics of shear bands

Shear bands appear at limit states of soil bodies. They are analysed as thin zones of localised deformation that takes place as simple (i.e. dilatant) shear. It can be observed, however, that shear bands are discontinuous and also may be “reflected” at rigid boundaries. These phenomena appear as incompatible with the assumed shear deformation. The analysis in this paper reveals the kinematics of such “incompatibilities” in terms of continuous deformation fields.     

土与混凝土接触面反向剪切单剪试验

土与混凝土接触面的力学行为是土与结构共同作用研究中的一个主要课题。进行了17 %、20 %、24 %共3组含水率的土与混凝土接触面正反向单剪试验,每组试验分别考虑5个法向应力和4个正向剪切比。试验结果表明,在正向剪切比和含水率一定时,接触面反向剪切破坏仍遵循摩尔-库仑破坏准则。当正向剪切比为0.50、0.75、1.00时,对应反向剪切强度分别为各自正向初始强度的90 %、75 %、55 %,对应的反向剪切黏聚力约为初始正向剪切黏聚力的95 %、80 %、54 %,反向剪切摩擦角约为初始正向剪切摩擦角的90 %、76 %、57 %。试验结果可供相关工程数值分析参考。