碎裂岩体的变形参数

岩体变形是表征岩体力学作用的重要方面之一。实验资料表明,坚硬的碎裂岩体变形可分为两个阶段,即在低应力水平条件下以结构面闭合为主的压密变形阶段;在高应力水平条件下则以结构体弹性变形为主的压缩变形阶段。因此,应     

一个考虑土的各向异性的孔压公式及其应用

为了研究粘土的各向异性对孔压生成的影响,在修正剑桥模型的基础上,采用关口-太田应力比概念、结合邢义川-郑颖人方程,构造了一个各向异性旋转屈服面,建立了一个各向异性弹塑性本构模型;据此推导出一个各向异性孔压表达式,该式可以考虑Lode角以及主应力轴的平面旋转对孔压的影响;并采用新的孔压表达式着重分析了三轴应力状态下Lode角旋转以及主应力轴旋转所造成的孔压发展,并对条形荷载下的平面应变各向异性粘土地基中的孔压发展进行了计算。计算结果表明,地基中由于Lode角旋转造成的孔压不明显,但在荷载边角位置主应力轴旋转造成的孔压不容忽视,尤其是在埋深相对较浅的位置。     

地铁行车荷载下隧道周围加固软粘土孔压特性试验

由于上海轨道交通四号线海伦路站隧道周围软土在地铁行车荷载作用下产生变形,使隧道发生局部开裂、渗水而需要对地铁隧道进行加固处理。通过上海地铁4号线海伦路站附近隧道周围加固软粘土进行应力控制的循环三轴试验,研究了地铁行车荷载作用下加固软粘土的动孔压发展情况,充分考虑了土体围压、固结比、轴向循环荷载的大小及频率对动孔压的影响。研究结果认为,其他条件相同时,加固软粘土孔压随振动次数、循环荷载幅值的增大而增大,随围压和加载频率的增大而减小,可以用二次对数关系曲线对加固软粘土残余孔压变化进行预测。     

复杂应力条件下掺砾黏土真三轴试验

采用新型真三轴仪器,对掺砾黏土进行了复杂应力条件下加载试验,近似模拟了土石坝填筑期心墙土体单元的加荷过程。试验结果表明,由于土体单元处于复杂应力状态,即使是单向加载这样的简单加荷应力路径,在不同应力方向上的应力和变形也都呈现显著的应力各向异性。土石坝应力变形分析中坝体单元处于三向应力条件下,由于加载引起的应力各向异性对心墙乃至整个坝体的应力变形规律都有较大影响,合理的本构模型应该能够反映并描述这种复杂应力状态下的应力各向异性。     

粘土的粘塑性特性试验与三要素本构模型

研究了3种粘土的未扰动试样和重塑试样在三轴排水固结试验条件下的粘塑性。在试验过程中,利用计算机控制应变控制式三轴仪的加载速度,实现了在不同加载阶段的不同恒应变率加载。依据应力对应变率改变的响应程度对粘土的粘塑性进行了评价。实验结果表明,粘土的粘塑性表现为等时特性,并且经过一定时间的蠕变后,粘土强度会有较大地提高。并指出粘土的粘塑性应力-应变特性可以较好地采用非线性三要素模型对它进行描述。     

交通荷载引起的静偏应力对饱和软粘土变形影响

为了研究交通荷载引起的静偏应力对饱和软粘土变形的影响,设计了室内不排水动三轴试验,将交通荷载简化为静偏应力与正弦荷载的叠加,依据实验数据分析了土体的塑性变形发展规律,给出了不同静偏应力下土体的转折应变-破坏振次的半对数关系曲线,研究了静偏应力对该曲线的影响规律。研究表明,静偏应力越大,土体变形发展越快,相同条件下达到转折应变时所需的破坏振次越小;静偏应力越大,转折应变-破坏振次关系曲线的斜率越小,截距则比较接近。     

湛江粘土的强度特性

本文从湛江粘土的抗剪特性及应力—应变特性两个方面,对雷州半岛下更新世河海三角洲相沉积粘土(湛江粘土)的强度特性进行了研究。湛江粘土(包括杂色、灰色两类)的直剪(快剪)及三轴不排水剪试验结果,均表明各类粘土的非均质性显著,两类粘土抗剪强度指标有明显差异。抗剪特性受含水条件、成分组成,结构联结、剪切方向及试验方法等因素影响。湛江粘土的应力—应变曲线主要有峰值型、平缓型两类。土类、含水条件及剪切方向直接影响到曲线的类型及曲线中各阶段变化差异。本文不仅有助于湛江粘土力学性质的全面研究,而且对湛江市工程建筑地基评价有一定的指导意义。     

上海地区粘土弹塑性应力—应变模型的研究

本文根据上海粘土的真三轴试验结果，对上海粘土弹性应力－应变模型的建立进行探讨，并研究了确定有关参数的方法。试验表明，模型中的参数均可能过常规三轴试验加以确定，这使上海地区采用弹塑性模型研究粘土成为可能。本文最后还利用该模型所得的计算值与试验结果了对比，取是了较理想的效果。     

单轴拉伸条件下岩石本构理论研究

利用损伤力学理论研究了细观非均匀性岩石拉伸应力应变关系,包括:线弹性阶段、非线性强化阶段、应力降阶段、应变软化阶段。所用的模型分析了岩石的细观各向异性对全过程应力应变关系的影响,分析了产生应力跌落和应变软化的主要原因是损伤和变形局部化,将损伤和变形局部化引入本构模型是和以往模型的重要区别。通过与实验成果对比分析验证了模型的正确性和有效性。     

高围压下冻结粘土的抗压强度试验研究

以取自华东某地的深部粘土为研究对象,根据室内单轴和三轴压缩试验的试验结果,分析了高围压下冻结粘土的应力-应变行为与单轴压缩条件下应力-应变行为的异同,并讨论了围压和温度对冻结粘土强度的作用.     

Processes of normal fault evolution in a siliciclastic sequence: a case study from Miri, Sarawak, Malaysia

Detailed field observations of normal faults formed at shallow depth in a deltaic sand–clay sequence near Miri, Sarawak are used to study the main structural elements during the early stages of fault development. We studied over 450 segmented faults, many of which contain clay smear, in an excellent outcrop exposing a collapsed crest structure.In agreement with previous studies we find that important elements of fault zone evolution are: (i) clay smear, (ii) telescoping on parallel strands, and (iii) preferred deformation of fault-bounded lenses. We model the consequences of telescoping on parallel strands and conclude that the reliability of juxtaposition diagrams can decrease dramatically in the presence of undetected multiple fault strands. The across fault connectivity can either increase or decrease depending on small variations in many of the input parameters.All the faults studied have a continuous clay smear over the interval studied, except for the places where a sand bed has an offset smaller than its thickness, and therefore has not moved past clay. Although on average the clay content observed correlates well with the average clay content of the faulted section, there are large variations in clay content controlled by local complexity in deformation. Understanding of this local complexity is a prerequisite for further improvement of clay smear in the subsurface.     

粘土的杨氏模量试验研究

三轴试验被应用于评定未扰动和重塑Kitan粘土的弹性性质。Kitan粘土的杨氏模量分别在最初加载、蠕变后,小的周期加载和滞回圈时测定。为了测定在应变小于0.01%时的准确性,试验采用局部位移测量传感器(LDT)。试验结果显示:在相同应力水平条件下,未扰动Kitan粘土的杨氏模量大于重塑土;对于同一种粘土,在应变率大的情况下,它的杨氏模量同样大;在应变小于0.01%时,未扰动Kitan粘土呈线弹性。      

The K-Ar system, lithomineralogical, and geostructural characteristics of the Jurassic terrigenous complex in the Northeastern Caucasus

The paper discusses changes in both mineral composition and structural-textural characteristics of the Jurassic terrigenous complex along the Avar Koisu River (Dagestan) profile that intersects rocks with significantly various types of deformation. The profile extends from the monoclinal zone to the intense deformation and cleavage development zone. The alterations are manifested in the change of clay mineral assemblages, polytype modifications of micaceous minerals and their crystallinity index, rock density, reflectance of vitrinite, and other properties. Growth of the degree of secondary alterations (primarily, cleavage intensity) is accompanied by an appreciable decrease in K-Ar age of rocks and simultaneous increase of their stratigraphic age.     

上海粘性土剪切带倾角的试验研究

采用可量测局部侧向应变的平面应变仪，对上海地区第（2）层褐黄色粉质粘土和第（6）层暗绿色粉质粘土的原状土样，进行固结不排水平面应变压缩试验，观察土样的局部化变形过程，量测剪切带倾角，研究剪切带倾角随固结压力的变化情况，计算剪切带倾角的传统土力学理论解并与实测值进行比较，根据剪切带内局部剪胀角的近似估算，初步研究剪切带内的变形机理，认为剪切带的形成与孔隙水的运动密切相关。     

卸荷作用下软黏土回弹吸水试验研究

为了研究软黏土试样在经受卸荷作用后回弹变形中的吸水规律,设计了新的渗透固结试验仪器。以饱和软黏土试样为研究对象,通过室内试验,分析了卸荷作用下软土的回弹吸水特点。试验结果表明,研制的渗透固结仪器密封性能好,可以收集试样固结过程中排出的孔隙水。软黏土试样在大于临界卸荷比的情况下发生回弹吸水,其规律与预压荷载持续时间有关。当预压荷载持续时间为主固结完成时,则软黏土试样回弹变形引起的体积变化等于进入土体的孔隙水的体积;若荷载持续时间为24 h,则回弹变形可以分为主回弹阶段与次回弹阶段。在主回弹阶段,土样的体积变化等于吸入土体的孔隙水的体积;在次回弹阶段,试样并未吸水,仍然有少量变形。卸荷后软黏土试样吸入土体的水量与固结沉降排出土体的水量之比普遍小于10%。     

甘肃天水地区强降雨诱发黄土-泥岩滑坡机理实验研究

在甘肃天水地区每年由降雨诱发的黄土-泥岩滑坡灾害事故很多,给当地人民生命财产造成巨大损失。为探索该类斜坡的滑动破坏过程与机理,在野外地质调查、工程地质钻探及岩土体力学测试的基础上,通过室内大型物理模型实验,研究“上部黄土+下部泥岩”二元结构类型斜坡在强降雨作用下的动态变形演化过程,揭示该类斜坡的破坏机理和破坏模式。结果表明:强降雨作用下斜坡变形破坏以滑动破坏为主,水分的作用主要表现为增加土体自重、引起土体强度降低、降低结构面的抗滑力、产生孔隙水压力及降低有效应力等几个方面,斜坡的破坏模式则主要表现为坡肩侵蚀→微裂隙产生、发展、贯通→斜坡局部滑动破坏→斜坡整体滑动破坏。研究结果对天水地区该类滑坡的早期识别有重要的参考意义,可为该类滑坡的防灾减灾提供科学依据。     

Experimental study on the vertical deformation of aquifer soils under conditions of withdrawing and recharging of groundwater in Tongchuan region,China

Land subsidence due to aquifer-system compaction accompanying groundwater extraction is a global hazard. Rising urban construction and groundwater demand necessitate increased awareness and better understanding of the geological problem. Motivated by the lack of laboratory-scale studies on this issue, an experimental investigation on the newly developed Tongchuan region, China, is presented. The study addresses the deformation behaviors of three soil samples, with the lithology of silty clay, silt, and fine sand, under the conditions of groundwater withdrawal and recharge using the GDS Consolidation Testing System. Results indicate that all three samples were characterized by elastic–plastic deformation under the conditions of withdrawing and recharging. The vertical deformation of the silty clay in the aquitard above the first confined aquifer was larger than those of the other two samples, and its deformation is a gradual and long process; thus, considerable attention should be paid to deformation in this aquitard due to the apparent creep effect and tiny rebound deformation. However, the settlement of the fine sand in the second confined aquifer cannot be ignored due to the great thickness of the aquifer. For the same soil, as the pore-water pressure declined, the unit rate of vertical deformation decreased gradually, whereas the creep effect of deformation in the later declining stage of pore-water pressure was more apparent than that in the former declining stage. These observations are highly important to the local government, which is developing measures to prevent and control subsidence.     

发震断裂带内黏土矿物的纳微米变形

断层泥是发震断裂最显著的物质标志之一,它保留着许多断层活动的信息.在野外宏观调查和显微视域观察基础上,利用SEM技术,从纳微米尺度,研究发震断裂带内黏土矿物的组合形态和变形样式,并对一些问题进行深入分析和讨论.黏土矿物在断层粘滑滑移过程中,出现定向排列,在正交偏光显微镜下表现为平行排列的消光带.在SEM视域下,可以观察到片状黏土矿物的定向排列,同时可以清晰地识别多次断层粘滑滑移事件.在断层泥中发现的蠕变滑移现象,带有普遍性.在显微视域下,黏土矿物表现为波状消光带.在SEM视域下,可以观察到片状黏土矿物的褶皱变形、流动变形、绕砾滑动、撕裂变形等.鉴于在同一个视域内,可以同时观察到粘滑滑移标志和蠕变滑移标志,通过分析其先后关系,发现蠕变滑移发生于粘滑滑移之前,对应于断层的亚失稳阶段的运动.      

Multiscale modeling of a sensitive marine clay

This paper examines the mechanical behavior of a sensitive marine clay. Various laboratory tests on intact and reconstituted samples of Guinea Gulf marine clay were performed under isotropic compression and drained triaxial compression at constant confining stresses. Microstructure analysis on intact and reconstituted samples was also carried out under different loading conditions. The effect of inter‐aggregates bonding on mechanical properties is discussed. Based on experimental analysis, a new modeling method is proposed. In this approach, the clay is regarded as an assembly of aggregates of clay particles. An inter‐aggregate contact law is introduced relating contact forces to aggregates relative displacements. The deformation of the assembly can be obtained by integrating the movement of the inter‐aggregate contacts in all orientations. Thus, the effect of inter‐aggregates bonds and debonding is considered in a direct way. The model is evaluated through comparisons between the predicted and measured results on Guinea Gulf marine clay. The evolutions of local stresses, strains, and bonds in inter‐aggregates planes are discussed to explain the anisotropy induced by the applied loading. Copyright © 2010 John Wiley & Sons, Ltd.     

基于强度折减的土质边坡破坏及稳定分析

边坡的破坏过程是由土体局部破坏向整体失稳发展的过程,其塑性区的开展及其水平位移增量的变化较完美地展现了这个过程。根据边坡的实际破坏和有限元数值模拟情况,提出了以特征点位移增量的突变及塑性区贯通作为边坡的失稳判断准则;并以此为判据,采用基于强度折减的大变形有限元方法分析了土质边坡的破坏及稳定性。研究表明,采用强度折减有限元法可有效分析边坡的破坏及其稳定性;此外还分析了带有软弱夹层黏土边坡的破坏性状及其稳定性,并比较了大、小变形有限元的计算结果,结果表明,带有软弱夹层黏土边坡的破坏性状随软弱夹层土体性质的变化而变化,由大小变形有限元分析得到的边坡稳定安全系数较为一致,但边坡的破坏机制随软弱夹层土体性质变化的转变点不同。