基于三维形态空间分析和仿真试验的岩体结构面剪切强度参数研究

获取结构面可靠的强度指标是研究岩体强度的重要基础。因不同结构面样本的巨大差异,以及剪切测试难以重复进行的实际情况,直接通过试验获取剪切参数通常难度较大且结果不理想。以具有定向变形特征的岩体剪切结构面为研究对象,探索性提出采用结构面剪切测试-结构面表面形态三维空间分析-数值仿真试验相结合方法,获取真实可靠的结构面强度参数。该方法优势表现为:岩体结构面摩擦角的2个组成部分即基本摩擦角和爬坡角完全分离,且能考虑结构面形态三维特性及剪切变形方向特征;同时,力学测试和数值试验结合,克服了单纯依靠剪切测试无法重复的重大难题。

考虑围压效应的非线性剪切强度参数模型

随着深部岩石工程的发展,围压对岩石强度的影响变得不可忽视,开展应力对岩石力学特性参数的研究,对评价深部岩石工程的稳定性具有重要的理论和工程意义。为了揭示深部岩石剪切强度参数的非线性特征,基于花岗岩三轴试验数据库,开展围压对剪切强度参数的影响规律研究,主要结论如下:(1)岩石的内聚力c随着围压的增大而增大,内摩擦角?随着围压的增大而减小;(2)建立了不同围压条件下的剪切强度参数c和?数据库,提出了考虑围压效应的非线性剪切强度参数模型;(3)误差分析结果表明,在没有三轴试验数据的情况下,非线性剪切强度模型有较好的岩石强度预测能力,90%的岩石强度误差小于20%。

聚乙烯醇纤维改良粘土对土强度及力学性能的影响研究

采用离散元软件PFC2D模拟了聚乙烯醇纤维对粘土的直接剪切试验,分析了聚乙烯醇纤维对粘土力学性能的影响,研究了添加纤维、纤维长度和纤维掺入质量比对聚乙烯醇纤维改良粘土力学特性的影响规律。研究结果表明,聚乙烯醇纤维改良粘土的粘聚力和内摩擦角均要高于素粘土,说明聚乙烯醇纤维显著地提高了粘土的力学性能;聚乙烯醇纤维掺入质量比越大,纤维改良粘土的剪切强度、粘聚力和内摩擦角越大,且纤维掺入质量比的增加明显地提高了改良粘土的粘聚力;随着聚乙烯醇纤维长度的增加,纤维改良粘土改良粘土的剪切强度、粘聚力和内摩擦角变化不大。

复杂节理岩体的剪切强度特性的尺寸影响研究

基于三维块体离散元软件3DEC程序,考虑存在三组节理的复杂节理岩体的情况,通过对10个不同尺寸的岩体块体进行直剪试验模拟,探讨岩体尺寸对于剪切强度特性的影响效果。由于剪切面相对节理面位置的不同,块体分为两组(第Ⅰ、Ⅱ组),得出了法向应力作用下的剪切应力与水平位移的关系曲线图。通过计算可得出剪切强度参数——黏聚力和摩擦角及其与块体尺寸的关系曲线。由此可见,两组的差异较大,故在进行选择参数时应根据剪切面的位置分别进行考虑。最后对岩体的剪切强度特性的尺寸效应进行了理论分析,认为节理岩体的剪切强度特性的尺寸影响的关键原因是节理结构面的存在,节理的相对位置、组数、间距、材料属性等都是重要的影响因素。

基于ANN-RBF方法对边坡岩体抗剪强度的预测

抗剪强度参数的选择对于边坡稳定性分析至关重要.为了保证数值分析的可靠性,建立了RBF神经网络模型预测边坡岩体的抗剪强度参数,并且收集了大量的工程数据修正和验证了这个模型.该模型可以预测任意一个边坡岩体的抗剪强度参数,并且计算结果非常接近于实测剪切实验结果,这证明了该模型的有效性和合理性.

图书馆书架用改性胶粘剂的制备与性能研究

为了提升图书馆书架用胶粘剂的胶接强度,研究了反应温度、反应时间、—OH与—NCO摩尔比、催化剂用量、热压温度和热压时间对聚氨酯胶粘剂中—NCO含量和胶粘剂试样剪切强度的影响。结果表明,胶粘剂体系中适宜的反应温度为70℃、反应时间为5 h、催化剂用量为0.1%、—OH与—NCO摩尔比为0.4。随热压时间的增加,试样的干状剪切强度(τ_(d))和湿状剪切强度(τ_(m))都先增大后保持稳定。随着热压温度(T r)从130℃增至150℃,试样的τ_(d)和τ_(m)先增大后减小,当热压温度为140℃时取得最大值。在热压温度为140℃、热压时间为75 min时,胶粘剂试样具有最大的τ_(d)和τ_(m),且为适宜的热压工艺参数。

低温条件下花岗岩力学特性试验研究

从辽宁锦州拟建地下储库工程现场钻取典型花岗岩岩芯,进行不同冻结温度(-10℃～-50℃)和不同含水状态(干燥和饱和)的单轴及三轴压缩试验,分析岩石的变形破坏规律、干燥和饱和状态抗压强度以及三轴剪切强度参数c,?值随温度的变化关系。试验结果表明:(1)无论干燥还是饱和试样,微风化花岗岩单轴及三轴抗压强度随着低温温度的降低而提高,但呈现非线性增加的趋势,得到花岗岩抗压强度随低温温度变化的非线性关系拟合式,并认为微风化花岗岩存在一个抗压强度趋于稳定的温度界限值,此值约为-40℃;(2)微风化花岗岩在干燥和饱和条件下,黏聚力c值随温度的降低而增大,在干燥条件下尤为明显。干燥条件下,微风化花岗岩内摩擦角随低温温度降低变化较小,摩擦角基本保持在57°左右,饱和条件下,微风化花岗岩内摩擦角随温度降低而增加,由-10℃～-50℃增长幅度约为3.43%。该研究成果可为液化天然气(LNG)的低温地下存储提供一定的力学参数依据。

岩石细观特征对其宏观力学行为的影响

采用颗粒流数值分析方法模拟砂岩试件在单轴和常规三轴压缩情况下的力学行为,获得三轴压缩强度,并根据摩尔-库伦强度准则,反算黏结力c和内摩擦角φ。探讨颗粒细观参数:颗粒接触刚度比、平行黏结刚度比、颗粒接触模量、平行黏结弹性模量与摩擦因子对岩石抗剪强度参数和单轴抗压强度的影响,研究结果表明:1)数值模拟与理论计算所得的单轴抗压强度随细观参数的变化趋势大致相同,但数值模拟结果小于理论计算值;2)平行黏结弹性模量与摩擦因子对轴向应力峰值影响较大;3)颗粒摩擦系数与材料内摩擦角呈近似对数相关。颗粒接触刚度比与平行黏结刚度比对材料内摩擦角的影响较大;4)平行黏结弹性模量对岩石黏结力的影响较其他细观参数大。颗粒接触刚度比与颗粒接触模量和黏结力呈正相关关系,而平行黏结刚度比、平行黏结弹性模量和摩擦因子与黏结力呈负相关关系。

试论某公路滑坡地质勘察及治理

以公路施工引起的工程滑坡为例,通过对该滑坡的主要工程地质特征及其成因分析,介绍了滑坡勘察与整治设计中确定滑动带剪切强度参数的一种途径、方法,提出了合理的滑坡治理方案。同对也箍出了评价工程建设对环境地质条件改变的重要性。

Physical and mechanical properties of sandstone containing a single fissure after exposure to high temperatures

In order to investigate the physical and mechanical properties of sandstone containing fissures after exposure to high temperatures,fissures with different angles α were prefabricated in the plate sandstone samples,and the processed samples were then heated at 5 different temperatures.Indoor uniaxial compression was conducted to analyze the change rules of physical properties of sandstone after exposure to high temperature,and the deformation,strength and failure characteristics of sandstone containing fissures.The results show that,with increasing temperature,the volume of sandstone increases gradually while the quality and density decrease gradually,and the color of sandstone remains basically unchanged while the brightness increases markedly when the temperature is higher than 585 ℃;the peak strength of sandstone containing fissures first decreases then increases when the temperature is between 25℃and 400℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature,and the mechanical properties of sandstone show obvious deterioration after 400 ℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature;with increasing angle αof the fissure,the evolution characteristics of the macro-mechanical parameters of sandstone are closely related to the their own mechanical properties.When the temperature is 800 ℃,the correlation between the peak strength and average modulus of sandstone and the angle α of the fissure is obviously weakened.The failure modes of sandstone containing fissures after high temperature exposure are of three different kinds including:tensile crack failure,tensile and shear cracks mixed failure,and shear crack failure.Tensile and shear crack mixed failure occur mainly at low temperatures and small angles;tensile crack failure occurs at high temperatures and large angles.

Shear creep parameters of simulative soil for deep-sea sediment

Based on mineral component and in-situ vane shear strength of deep-sea sediment, four kinds of simulative soils were prepared by mixing different bentonites with water in order to find the best simulative soil for the deep-sea sediment collected from the Pacific C-C area. Shear creep characteristics of the simulative soil were studied by shear creep test and shear creep parameters were determined by Burgers creep model. Research results show that the shear creep curves of the simulative soil can be divided into transient creep, unstable creep and stable creep, where the unstable creep stage is very short due to its high water content. The shear creep parameters increase with compressive stress and change slightly or fluctuate to approach a constant value with shear stress, and thus average creep parameters under the same compressive stress are used as the creep parameters of the simulative soil. Traction of the deep-sea mining machine walking at a constant velocity can be calculated by the shear creep constitutive equation of the deep-sea simulative soil, which provides a theoretical basis for safe operation and optimal design of the deep-sea mining machine.

Stability analyses of vertically exposed cemented backfill:A revisit to Mitchell's physical model tests

Mitchell's solution is commonly used to determine the required strength of vertically exposed cemented backfill in mines. Developed for drained backfill, Mitchell model assumed a zero friction angle for the backfill. Physical model tests were performed. Good agreements were obtained between the required strengths predicted by the analytical solution and experimental results. However, it is well-known that zero friction angle can only be possible in terms of total stresses when geomaterials are submitted to unconsolidated and undrained conditions. A revisit to Mitchell's physical model tests reveals that both the laboratory tests performed for obtaining the shear strength parameters of the cemented backfill and the box stability tests were conducted under a condition close to undrained condition. This explains well the good agreement between Mitchell's solution and experimental results. Good agreements are equally obtained between Mitchell's experimental results and FLAC3 D numerical modeling of shortterm stability analyses of exposed cemented backfill.

深部巷道破裂围岩强度衰减模型及其在FLAC^(3D)中的实现

基于深部巷道破裂围岩强度衰减规律研究成果,选择塑性参数作为损伤因子,根据室内预制初始损伤破裂岩样加卸载及其各级围压下的三轴压缩两试验结果,分别计算不同损伤破碎程度岩样卸载点的塑性参数值(初始损伤因子值)及其剪切强度参数c,φ值,初步建立深部巷道破裂围岩强度衰减模型;通过对初步建立的强度衰减模型中塑性参数的替换推导,建立以塑性参数εps表示的深部巷道破裂围岩强度衰减模型,使其可以直接运用于理论分析和数值模拟;将该模型植入FLAC3D中,结合实际深部巷道工程,对千米深井深部典型变形破坏巷道进行数值模拟分析,将数值模拟结果及相关结论与室内物理模拟和工程现场测试结果进行综合对比分析,验证了所建立模型的合理性。

土体含水率与滑坡风险相关性实验研究

降雨入渗容易造成边坡滑坡自然灾害,含水率是影响土体抗剪强度的关键因素之一。本文以滑坡区红黏土为研究对象,制作了5组不同含水率的土样,并在不同垂直压力下进行快速剪切实验,得到每组对应的剪切强度参数,研究了含水率与剪切强度参数之间的关系。利用实验所得到的土工参数进行高地下水位边坡稳定性数值模拟,拟合得到边坡坡顶含水率与边坡安全系数的关系。结果表明:含水率从10%增加到25%,红黏土强度指标粘聚力、内摩擦角约分别下降50%和30%;含水率与粘聚力和内摩擦角间均呈半对数关系;边坡坡顶含水率增加导致边坡安全系数近似成二次曲线下降趋势。