干湿循环泥质白云岩扩容特性及本构模型

为探究干湿循环作用下岩石性能劣化效应,以泥质白云岩为研究对象,针对其实际赋存环境开展干湿循环试验。研究了不同干湿循环作用下泥质白云岩的扩容特性及力学参数;并基于Mohr-Coulomb强度准则建立泥质白云岩统计损伤本构模型。结果表明:岩样的最大体积应变随围压的增大而增大;扩容应力与峰值应力之比随围压呈线性递增关系;扩容应力随围压的增大而线性增大,但其增长速率随干湿循环次数的增大而减小;随着干湿循环作用增强,峰值点的粘聚力降低,内摩擦角增大;扩容点的粘聚力与内摩擦角变化幅度均大于峰值点处,表现为扩容点受干湿循环的影响效应比峰值点处更为敏感;基于Mohr-Coulomb强度准则建立的统计损伤本构模型能描述泥质白云岩三轴压缩的应力–应变关系。     

酸性环境干湿循环作用对泥质砂岩力学参数的劣化研究

针对降雨和库水位升降对库岸边坡消落带岩体力学参数的劣化问题,选取泥质砂岩进行不同p H水环境干湿循环作用下的单轴与三轴压缩试验,结合室内试验结果,应用广义Hoek–Brown准则求得不同地质强度指标评分(GSI)下岩体的单轴抗压强度、弹性模量、材料常数和黏聚力。研究表明:破碎程度越大的泥质砂岩受浸泡的溶液酸性越强、干湿循环次数越多,其力学参数劣化程度就越高;在同一个GSI评分下,泥质砂岩各个力学参数随p H值和干湿循环次数n的劣化效应排序有所差异,综合劣化效应最大为弹性模量,累积劣化效应最明显为黏聚力,其劣化系数与浸泡溶液的p H值、干湿循环次数的对数ln(n)成线性相关。基于上述研究提出了泥质砂岩力学参数与p H值、干湿循环次数n的三维劣化方程,为酸性环境干湿循环作用下现场岩体力学参数的获取以及边坡稳定性寿命的预测提供了理论依据。     

含水合物沉积物等效弹性模量混合律模型

水合物开采安全性评价亟需合理的含水合物沉积物本构关系模型,而等效弹性模量的准确预测是建立合理本构关系模型的重要前提条件。本文基于复合材料经典的应力串联和应变并联模型提出了含水合物沉积物等效弹性模量的细观力学混合律模型,与三轴压缩试验结果对比验证了该模型的适用性。研究结果表明:等效弹性模量细观力学混合律模型的模型参数少,且物理意义明确,其预测结果与试验数据符合良好;含水合物沉积物的割线模量随水合物饱和度与有效围压的增加而变大。     

泥质软岩高边坡湿化稳定性研究

以一实际泥质软岩高边坡为分析对象,通过原状土样的室内试验成果分析了该种土体的特殊力学特性;采用Bishop圆弧滑动法对边坡在天然状态、残余强度状态、湿化状态下的整体稳定性进行了计算;根据试验得到的Duncan模型参数对边坡在不同应力状态下的非线性应力-应变特征进行了有限元分析;并在不改变模型参数和计算方法的前提下对加固后的边坡进行了相应的计算,所得出的结果与边坡实际运行状态吻合,表明泥质软岩边坡的设计与分析必须考虑水的入渗和卸荷松弛所导致的土体强度的衰减。     

CPTU数据校准上海深层软土参数的随机力学-贝叶斯方法

城市深层地下空间的开发需要开展科学计算。合理的本构模型和准确的岩土参数是岩土力学分析的两大支撑。修正剑桥模型（modified cam-clay, MCC）的岩土参数简单直观,被广泛应用于岩土工程实践。室内土工试验由于取样扰动、试验误差等不可避免的缺陷,难以精确获得深层岩土参数。结合先验知识、室内试验数据和孔压静力触探（piezocone penetration test, CPTU）测试数据,将关键岩土参数视为随机变量,采用随机力学-贝叶斯方法,校准深层软土的关键岩土参数,如临界状态应力比、压缩系数、回弹系数和超固结比。以上海市苏州河深层排水调蓄管道系统工程——云岭竖井基坑工程为背景,以基础底板处的深部第(8)层土为研究对象。首先,利用MCC模型的柱孔扩张理论,揭示了CPTU数据（锥尖阻力、侧摩阻力和孔隙水压力）与极限扩孔应力之间的力学转换机理,利用苏格兰Bothkennar岩土试验场地的试验数据,验证CPTU测试数据力学模型的适用性;其次,建立关键岩土参数与CPTU数据之间的二次非交叉响应面,利用MCMC(Markov-chain Monte Carlo)抽样算法,获得关键岩土参数...     

旁压试验在深厚强风化花岗岩层中的应用

强风化花岗岩地层在以深圳为代表的广东地区广泛分布,其特点为结构性强、埋深较深、层厚较大、刚度大且刚度变化大。由于其结构性强且破碎,在进行岩土工程勘察取样时极易被扰动,导致室内土工试验的结果无法反映岩土体真实的力学性质;由于其刚度大,标准贯入试验无法有效实施;由于其层厚大且刚度变化大,故实际工程中亟需可以测定沿深度连续变化的岩土力学参数的手段。旁压试验是一种适应性强的原位试验方法,可以较好地满足以上要求。本文结合笔者的工程实践,介绍了旁压试验在深圳地区深厚强风化花岗岩层中的应用,并与室内试验等其它手段得到的力学参数进行了对比,结果表明,旁压试验得到的承载力等各项指标均高于室内试验结果。此外,本文还提出了在深厚强风化岩层中进行旁压试验需要注意的事项,供同行参考。     

不同应力路径下灰砂岩力学特性与强度参数研究

基于常规岩石力学试验设备与自行研制的岩石空心圆柱扭剪试验系统,开展灰砂岩直剪试验、常规三轴压缩试验与空心圆柱三轴压缩(内外压相等与内外压不等)试验,研究不同应力路径下岩石的力学特性和强度参数。通过比较常规三轴压缩试验与空心圆柱三轴压缩(内外压相等)试验结果,验证了岩石空心圆柱扭剪试验系统以及采用空心圆柱试样进行试验的可行性,内外压不等的空心圆柱三轴压缩试验可以反映中间主应力对强度参数的影响。通过比较不同类型试验获取的灰砂岩强度参数,认为按D-P准则整理的岩石空心圆柱三轴压缩(内外压不等)试验数据,获取的强度参数能合理地反映应力状态和应力路径的影响。     

干湿循环作用下泥质白云岩能量机制试验研究

为研究干湿循环作用下泥质白云岩力学特性和能量机制,利用MTS851.03岩石力学试验系统分别对干湿循环0次、40次及60次试样进行三轴压缩试验,分析了3种状态下泥质白云岩损伤破坏过程中的能量演化规律,并以可释放弹性应变能为统计分布变量,基于Weibull分布建立泥质白云岩的损伤统计本构模型。结果表明：3种状态下试样峰值强度与围压的回归关系符合主应力表达的Mohr-Coulomb准则特征;泥质白云岩试样能量实时演化过程具有阶段性;干湿循环作用使泥质白云岩的内部损伤和塑性变形加强;峰值点处试样各应变能随围压线性增大,储能极限随干湿循环次数逐步减小;以可释放弹性应变能为统计分布变量建立的损伤统计本构模型能较好模拟试样三维条件下的应力-应变关系。     

北京第三系粘土岩的工程特性研究

在北京市区西部工程建设中常遇到第三系粘土岩,特殊的成岩历史和成岩作用使其具有独特的工程特性。本文以第三系粘土岩的现场观测及室内试验结果为基础,研究了第三系粘土岩的地质特征、物理力学性质,并对其环境影响效应及开挖条件下强度的变化进行了分析,提出基坑施工时应采取适时快速开挖、快速封闭和围（支）护的处理方法。研究结果对工程建设具有一定参考价值。     

泥质膨胀岩工程地质研究

220 kV草坝变电站场地内广泛分布的第三系砂质泥岩和泥岩具有膨胀性。本文首先探讨了泥质岩膨胀性的划分标准;其次,通过对试验结果的分析、研究,初步判定了工程区段泥质膨胀岩的工程特性;最后,探讨了泥质膨胀岩地基处理的工程对策。     

Experimental study on the determination of strength of masonry walls

The results of a research project carried out on masonry panels obtained from structures struck by the Umbria-Marchigiano earthquake of 1997–1998 are presented. The project consists of two parts: tests were performed in the laboratory, and in situ in order to determine the correct parameters describing masonry behavior. With regard to the laboratory tests, several compression tests were performed on cylindrical stone samples. Stone samples were obtained from the panels on which in situ tests had been previously carried out. Depending on the three types of in situ tests carried out (compression test, diagonal compression test, shear–compression test), different dimensions of panels were used using an appropriate cutting technique in order to leave the panels undisturbed. The shear strength and the Young and shear elastic modulus were measured. These results were compared with the values suggested by different standards. The experimental research allowed to characterize the mechanical properties of some typical masonry walls in old buildings of Umbria. These results are reported, together with an analysis of the masonry textures and sections.     

Creep and time-dependent damage in argillaceous rocks

This paper presents the results of laboratory tests on the time-dependent behaviour of three rocks characterized by a high proportion of clay particles. The viscosity of these sedimentary rocks was studied under different loading conditions in uniaxial compression: static or cyclic creep tests and quasistatic tests (low-loading strain rate) were performed across various orientations of fabric planes.The quasistatic tests showed similarities in the mechanical response of these three argillaceous rocks: a late phase of dilation and a linear development of volumetric deformation before the beginning of unstable crack propagation. The development of secondary and tertiary creep phases during the creep tests highlighted the existence of a deviatoric stress threshold, below which only primary creep is observed. Long-term creep tests also showed that the volumetric variation is not constant during the development of viscoplastic deformations.A microstructural analysis of thin sections extracted from specimens after the tests, gave evidence of cataclastic and granular creep. Damage to the argillaceous matrix occurs and no cracks were observed in the quartz and carbonate grains. This evidence was also demonstrated for tests with loading at a high strain rate.Finally, this study highlights the significant viscoplasticity of argillaceous rocks. The mechanical properties deteriorate rapidly when crack propagation becomes unstable and the viscoplastic strains seem to be due to clay particle slips, known as granular creep.     

Analysis of hydro-mechanical processes in a ventilated tunnel in an argillaceous rock on the basis of different modelling approaches

In this paper, a modelling benchmark exercise from the DECOVALEX-2011 project is presented. The bench-mark is based on the performance and results of a laboratory drying test and of the ventilation experiment (VE) carried out in the Mont Terri Underground Rock Laboratory (URL). Both tests involve Opalinus clay. The work aims at the identification, understanding and quantification of mechanisms taking place during the ventilation of a gallery in argillaceous host rocks on one hand and at investigating the capacity of different codes and individuals to reproduce these processes on the other hand. The 4-year in situ VE took place in a 1.3 m diameter unlined tunnel and included two resaturation-desaturation cycles. The test area was equipped with over one hundred sensors (including the global water mass balance of the system, relative humidity (RH), water content, liquid pressure, relative displacement and concentration of some chemical species) to monitor the rock behaviour during ventilation. The laboratory drying experiment, carried out before the VE, was designed to mimic the in situ conditions. The work was organized in a progressive manner in terms of complexity of the computations to be performed, geared towards the full hydro-mechano-chemical (HMC) understanding of the VE, the final objective. The main results from the modelling work reported herein are that the response of the host rock to ventilation in argillaceous rocks is mainly governed by hydraulic processes (advective Darcy flow and non-advective vapour diffusion) and that the hydro-mechanical (TM) back coupling is weak. A ventilation experiment may thus be regarded as a large scale-long time pump test and it is used to determine the hydraulic conductivity of the rock mass.     

深部原位岩石力学构想与初步探索

深部资源开发的基础是研究深地科学规律,关键是探明不同赋存深度原位环境对岩石物理力学行为影响的差异性规律.适用于浅部资源开采的岩石力学实验与理论研究很难充分考虑不同深度原位赋存环境对岩石物理力学特征和工程的影响.提出"深部原位岩石力学"构想的定义和内涵,利用取自松科二井同一地质区域的10个不同深度(1 000?6 400...     

考虑颗粒破碎的砂土高应力一维压缩特性颗粒流模拟

以Toyoura砂室内高应力一维压缩试验结果为基础,利用二维颗粒流方法中的接触黏结模型生成簇颗粒单元来模拟实际砂土的颗粒破碎特性。高应力一维压缩数值试验中,数值试样由887个簇颗粒单元组成。数值试验与室内试验结果对比表明:数值试验得到的压缩曲线形状及颗粒破碎屈服应力大小均与Toyoura砂室内试验结果一致,说明数值试验能够较好地再现实际砂土在高应力一维压缩条件下的颗粒破碎特性。与室内试验相比,利用数值试验不仅能得到宏观的颗粒破碎现象,而且还能通过分析内部接触力的变化和对黏结破裂位置的追踪来研究颗粒破碎的细观演化规律,从而可进一步探讨颗粒破碎的细观力学机制。最后,就细观参数、加荷速率、簇颗粒数量及试样平均粒径等因素变化对数值试验结果的影响进行了分析。     

Anisotropic modelling of Opalinus Clay behaviour:From triaxial tests to gallery excavation application

Deep repository in geological formations is the preferential solution considered in many countries to manage high-level nuclear wastes. In Switzerland, the Opalinus Clay is a candidate host rock. In this context, in situ and laboratory tests are conducted on Opalinus Clay to demonstrate the feasibility of deep disposal in this argillaceous formation. This paper presents a constitutive model able to fit the experimental data obtained from some triaxial tests conducted by Jahns(2013) on cores from borehole Schlattingen SLA-1. The elasto-plastic behaviour of Opalinus Clay is reproduced thanks to a DruckerPrager model, taking into account the anisotropy behaviour of this sedimentary rock. The objective is to employ a single set of parameters representative of the material. In a second version of the model, the stress-dependence of the elastic properties and damage are taken into account. Finally, the parameters calibrated with experimental tests are used to simulate the excavation of a gallery with a second gradient approach.     

水泥粉喷桩桩体水泥黑土力学性质试验研究

根据原状黑土、不同水泥掺入比和养护龄期人工配制的水泥黑土试块、水泥粉喷桩桩体钻芯试件的物理力学性质测试数据以及水泥黑土X射线衍射 (XRD)和扫描电镜 (SEM)测试结果 ,分析了水泥粉喷桩桩体水泥黑土无侧限抗压强度和模量随水泥掺入比及养护龄期的变化规律、水泥黑土强度形成机理以及室内外水泥黑土无侧限抗压强度相关关系 ,提出了水泥粉喷桩桩体水泥黑土的水泥掺入比建议值