共查询到19条相似文献，搜索用时 315 毫秒
1.
在理论分析的基础上,利用试验结果模拟分析单轴压力作用下含裂隙恐龙化石断裂损伤过程。在FLAC3D中采用FISH语言编写了基于体元分析的计算程序,采用弹脆性本构模型,分析了试验过程中恐龙化石的裂纹萌生→扩展→贯通规律和裂隙化石的断裂损伤机制。在单轴压缩作用下,含有裂隙的恐龙化石试件的破坏过程主要分三个阶段:即线性变形阶段、非线性变形阶段和软化阶段,当载荷超过应变峰值强度后,化石内部将生成大量新的诱导裂隙,导致化石内部结构发生剧烈变化。值得注意的是,恐龙化石峰后的强度软化过程非常不稳定,峰值附近的材料力学行为对化石试件内部缺陷的分布十分敏感。试验表明,有裂隙恐龙化石的抗压强度值比无裂隙恐龙化石的抗压强度值小30%,最终的残余抗压强度也略小,在加载应力作用下,相比不含内部裂隙的恐龙化石,内含裂隙的恐龙化石其内部裂隙会迅速大量扩展,加重了恐龙化石的风化程度和破坏速度。 相似文献
2.
岩石蠕变特性对岩体工程的长期稳定有着重要影响, 尤其是在酸雨等水化学作用下, 岩石的细观结构遭到破坏, 蠕变特性及变形更为显著。以重庆二佛寺红层砂岩为研究对象, 通过开展室内三轴压缩分级蠕变试验, 研究了酸腐蚀状态下砂岩的蠕变特性。结果表明: 酸的腐蚀和浸泡会使砂岩内部孔隙增加, 导致砂岩在第一级荷载下会产生较大的瞬时应变和蠕变量, 之后瞬时应变量和蠕变量随着应力增加而增大; 岩样受到腐蚀软化, 蠕变破坏强度为抗压强度的76%, 长期强度仅为抗压强度的54%。为了描述蠕变全过程, 建立了一个损伤蠕变模型来拟合试验数据, 验证了其适用性, 可以为岩土工程建设的稳定性提供参考。 相似文献
3.
三峡库区广泛分布侏罗系红砂岩, 在水库运行期间红砂岩的渗流-应力耦合特性关乎库区内多数滑坡和岩质边坡的稳定性。借助岩石多场耦合三轴试验系统, 对三峡库区侏罗系红砂岩开展了不同围压、不同渗透压下的三轴压缩试验, 系统研究了红砂岩的三轴压缩力学特性和渗透率演化特征。研究结果表明: ①红砂岩的峰前应力-应变曲线可分为孔隙压密阶段、弹性变形阶段、微裂隙稳定发展阶段和非稳定发展阶段。红砂岩的力学参数与渗透压的关系呈负相关, 与围压呈正相关。②随着围压升高, 红砂岩的破坏模式由张拉破坏过渡到剪切破坏。③不同渗透压下, 渗透率曲线呈平稳发展→缓慢上升→快速上升3阶段演化规律; 不同围压下, 渗透率曲线先降低后升高。④从能量角度分析了渗透压和围压对岩石的作用, 验证了渗流对岩石的劣化效应以及围压对裂纹发展的抑制作用。本试验对鲜有报道的侏罗系红砂岩的强度、变形和渗透特性做了系统的研究, 对渗流-应力耦合课题有补充意义。其工况根据三峡库区边坡岩体的应力水平来确定, 试验结果对分析库区边坡稳定性具有指导意义。 相似文献
4.
赋存于地球深部的地热资源,以其储量丰富、清洁再生等优势,有望成为破解我国能源困局,助推“双碳”目标实现的重要途径之一。干热岩(HDR)开发过程中,面临着高温高压环境下水-岩作用问题,在温度场、渗流场、应力场、化学场(THMC)等多场耦合作用下,岩体应力腐蚀效应和疲劳劣化会诱发岩石微裂纹-裂缝扩展、成核与丛集行为,进而影响增强型地热系统(EGS)的热交换效率和地质体稳定性,这也是制约干热岩长期安全开发的瓶颈,亟待突破。通过总结现有干热岩高温高压下多场损伤研究中的实验探索、理论模型、数值分析等多手段跨尺度方法,分析干热岩在高温高压及水环境下的应力腐蚀效应,可阐明循环生产过程中低温工质与高温地质体循环换热下干热岩储层结构演化的动态过程及工程响应,进而揭示THMC多场耦合作用下干热岩储层疲劳劣化损伤机理,为我国深部地热资源高效安全开发提供理论支撑和地质保障;但仍亟待深入开展增强型地热系统的THMC多场耦合作用下岩体应力腐蚀效应的干热岩疲劳劣化机制与长期稳定性研究,如考虑应力腐蚀效应和疲劳损伤的干热岩长期强度评价模型、基于跨尺度疲劳损伤评价的干热岩开发下地质体长期稳定性方法、适应于干热岩储层改造... 相似文献
5.
自然界中岩石内部均存在一定程度的损伤,损伤的持续演化过程对岩体的稳定性极为不利。为了研究岩石的损伤演化过程,将岩石分为未损伤部分、闭合裂隙部分与张开裂隙部分,采用统一强度理论与统计损伤理论分析岩石微元强度的分布,通过分析变形协调条件下各部分的应力-应变特征得到岩石的损伤本构模型与损伤演化模型,与巴东组紫红色泥岩三轴压缩试验结果对比验证后将模型应用于某反倾层状岩质边坡的破坏深度分析。分析结果表明:提出的损伤本构模型可以较好地模拟巴东组紫红色泥岩的三轴压缩应力-应变特性,提出的损伤演化模型可以较好地分析巴东组紫红色泥岩的损伤演化过程,且模型参数具有明确的物理意义;此外,根据基于损伤演化模型的反倾层状岩质边坡破坏深度修正模型计算得到的结果偏保守,用于岩土工程设计偏安全。 相似文献
6.
寒区岩石的力学特征往往受到冻融循环和荷载的共同影响,冻融岩石单轴压缩破坏断口蕴含着与冻融循环和荷载有关的损伤演化信息,冻融岩石单轴压缩破坏断口研究对冻融岩石断裂破坏机理分析有重要价值。为研究冻融岩石单轴压缩破坏断口形貌特征及其与宏观力学参数之间的关联性,通过摄影观测经历不同次数冻融循环的砂岩单轴压缩破坏断口形貌,采用像素点覆盖法计算断口分维值,探究了断口分维值与宏观力学参数之间的关系。结果表明:随着冻融次数的增加,冻融砂岩的力学性能劣化,单轴抗压强度、弹性模量、断口分维值、耗散能密度逐渐减小,峰值应变增大;单轴抗压强度、弹性模量、耗散能密度均与断口分维值之间存在指数关系,断口分维值越大,对应的单轴抗压强度、弹性模量、耗散能密度越大。冻融岩石单轴压缩破坏断口分维值可作为寒区岩体断裂破坏机理分析的有效参数。 相似文献
7.
泾河下游黄土台塬区侵蚀诱发的黄土滑坡不仅威胁当地居民的生命财产安全,而且引发严重的水土流失 及文物损毁等问题.以该类黄土滑坡为研究对象,在详细地质调查的基础上,取唐家村 L２滑坡坡脚原状黄土进 行减Χ压三轴剪切(RTC)试验,研究了饱和黄土的应力、孔压、Χ压特征以及剪切速率对土体力学行为的影响. 结果表明,RTC应力·径下Χ压率达到０．５５时,土体会因偏应力增大而引起塑性剪切破坏;同时,该应力·径下 的饱和黄土内摩擦角很小,仅为１０．７°;RTC应力·径下的破坏面,十分接近 K０ 状态面,说明天然斜坡坡脚饱和 黄土在小幅水平应力降低条件下易于发生破坏,从而诱发滑坡失稳. 相似文献
8.
基于有限元数值模拟技术,利用GPS数据获取喜马拉雅东构造结区域的断裂运动状态和构造应力场,并结合区域滑坡隐患探讨构造活动对滑坡灾害发育的影响。结果显示,差异化的断裂运动会造成显著相异的构造应力分布,而区域滑坡灾害更集中分布在断层锁固引起的构造应力异常区域;对应力异常区的斜坡进行稳定性研究发现,受应力长期累积影响,斜坡表层应力场持续扰动,造成潜在危险滑移面安全系数降低,促进滑坡失稳。研究表明,断裂构造运动模式可对区域滑坡灾害的发育和分布造成不可忽视的影响,且长期持续的构造应力荷载将促进滑坡灾害的发育。 相似文献
9.
滑坡是水库库区主要地质灾害类型之一,开展水库滑坡成因机制研究具有重要理论意义和工程应用价值.利用WebofScience(WoS)数据库和VOSviewer文献计量工具对1999-2018年已发表的969篇以水库滑坡为主题的相关论文进行研究趋势分析.文献计量分析表明三峡库区滑坡稳定性和变形研究是未来水库滑坡成因机制研究主要趋势.从库水对滑坡的宏观力学作用方式、库水作用下岩土体渗流应力耦合机理和库水对岩土体劣化作用过程等方面,对国内外水库滑坡成因机制研究的主要成果与进展进行了综述.综合现有的研究成果指出水库滑坡在精细化地质建模、岩土体多场耦合特征参数获取和岸坡长期演化评价等方面尚存在不足.基于上述问题,提出水库滑坡成因机制研究应以多场信息监测为重要手段,立足多学科交叉,采用大数据融合与挖掘和人工智能技术等解决水库滑坡长期演化趋势难题.考虑水库滑坡所处地质环境的复杂性,建议未来应在水库滑坡立体精细地质建模、多场关联监测、地质结构多场多尺度演变过程、基于监测数据大数据分析的滑坡预警阈值确定和原位试验综合平台构建等方面进一步深入研究. 相似文献
10.
水对岩土体的力学参数存在明显的劣化效应。开展了不同含水率条件下滑坡堆积体三轴力学试验, 建立了饱和度和力学参数之间的经验方程; 对建立的经验方程进行了二次开发, 通过饱和度和力学参数的耦合, 实现了库水位实时变动过程中考虑岩土体力学参数变化对滑坡稳定性的影响, 克服了库水位变动过程中岩土体物理力学参数不能随库水入渗变化的局限性。通过云南省兰坪县大华滑坡在库水位变动环境下的模拟结果和现场监测数据的比对, 验证了考虑岩土体力学参数水致劣化效应的合理性, 并对大华滑坡考虑水致劣化效应的变形演化规律进行了工程应用。 相似文献
11.
Undrained behaviour of sand under low cell pressure was studied in static and cyclic triaxial tests. It was found that very loose sand liquefies under static loading with the relative density being a key parameter for the undrained behaviour of sand. In cyclic triaxial tests, pore water pressures built up during the cyclic loading and exceeded the confining cell pressure. This process was accompanied by a large sudden increase in axial deformation. The necessary number of cycles to obtain liquefaction was related to the confining cell pressure, the amplitude of cyclic loading and the relative density of sand. In addition, the patterns of pore water pressure response are different from those of sand samples with different relative densities. The test results are very useful for expounding scour mechanism around coastal structures since they relate to the low stress behaviour of the sand. 相似文献
12.
《中国海洋大学学报(英文版)》2021,(5)
Marine geological disasters occurred frequently in the deep-water slope area of the northern South China Sea, especially submarine landslides, which caused serious damage to marine facilities. The cyclic elastoplastic model that can describe the cyclic stress-strain response characteristic for soft clay, is embedded into the coupled Eulerian-Lagrangian(CEL) algorithm of ABAQUS by means of subroutine interface technology. On the basis of CEL technique and undrained cyclic elastoplastic model, a method for analyzing the dynamic instability process of marine slopes under the action of earthquake load is developed. The rationality for cyclic elastoplastic constitutive model is validated by comparing its calculated results with those of von Mises model built in Abaqus. The dynamic instability process of slopes under different conditions are analyzed. The results indicate that the deformation accumulation of soft clay have a significant effect on the dynamic instability process of submarine slopes under earthquake loading. The cumulative deformation is taken into our model and this makes the calculated final deformation of the slope under earthquake load larger than the results of conventional numerical method. When different contact conditions are used for analysis, the smaller the friction coefficient is, the larger the deformation of slopes will be. A numerical analysis method that can both reflect the dynamic properties of soft clay and display the dynamic instability process of submarine landslide is proposed, which could visually predict the topographies of the previous and post failure for submarine slope. 相似文献
13.
Soil behavior can reflect the characteristics of principal stress rotation under dynamic wave and traffic loads. Unequal amplitudes of tensile and compressive stresses applied to soils have complex effects on foundation soils in comparison with the pure principal stress rotation path. A series of undrained cyclic hollow torsional shear tests were performed on typical remolded soft clay from the Hexi area of Nanjing, China. The main control parameters were the tensile and compressive stress amplitude ratio(α) and the cyclic dynamic stress ratio(η). It was found that the critical η tended to remain constant at 0.13, when the value of the compressive stress amplitude was higher than the tensile stress amplitude. However, the influence of the tensile stress was limited by the dynamic stress level when α= 1.For obvious structural change in the soil, the corresponding numbers of cyclic vibration cycles were found to be independent of α at low stress levels and were only related to η. Finally, a new method for evaluating the failure of remolded soft clay was presented. It considers the influence of the tensile and compressive stresses which caused by complex stress paths of the principal stress rotation. This criterion can distinguish stable, critical, and destructive states based on the pore-water-pressure-strain coupling curve while also providing a range of failure strain and vibration cycles. These results provide the theoretical support for systematic studies of principal stress rotation using constitutive models. 相似文献
14.
In this study, the undrained behaviour of silt under low stress level is studied. An effective preparation method for built—in
silt samples in the triaxial test was firstly developed. By triaxial testing of samples at low confining pressures it was
found that silt easily loses stability and liquefies. Loose silt may show temporary liquefaction under static loading, and
develop full liquefaction under cyclic loading. The most important factors influencing the silt behaviour are porosity, confining
pressure, consolidation state, cyclic loading level and number of cycles. The maximum obtainable shear stress is primarily
a function of the confining pressure and the internal frictional angle. The actual structure of the silt material is the key
factor in controlling its behaviour. 相似文献
15.
The aim of this study is to numerically investigate the influence of particle breakage on the mechanical behavior of granular materials using a discrete element method (DEM). To enable particle crushing, non-crushable elementary particles are boned together to represents the granular aggregates which can be crushed when the external force exceeds its strength. The flaw of the aggregate was also modeled by randomly distributed void. Single particle crushing tests were carried out to determine the distribution of particle strength. The results of single particle crushing tests illustrate that the simulated single particle fracture strength and pattern agree well with the Weibull’s distribution equation. Conventional oedometer tests, drained monotonic and cyclic triaxial tests were also carried out to investigate the crushing of the aggregates and the associated mechanical behaviors. The effect of confining pressure on the crushing of aggregates and the mechanical behavior was also analyzed. It was found that the peak stress and dilation decrease significantly when particle crushing was considered. The deformation behavior of the specimen is essentially controlled by two factors: particle rearrangement - induced dilation and particle crushing - induced contraction. The increase of permanent strain and the reduction of dilation were observed during cyclic loading and they tend to reach a stable state after a certain number of cycles. The crushing of aggregate is most significant in the first two cycles. The results also indicated that for the same axial strain the volumetric strain and the bound breakage in the cyclic loading tests are significantly larger than that in the monotonic loading tests, especially at high cyclic stress ratio. 相似文献
16.
Debris flow is one of the major secondary mountain hazards following the earthquake. This study explores the dynamic initiation mechanism of debris flows based on the strength reduction of soils through static and dynamic triaxial tests. A series of static and dynamic triaxial tests were conducted on samples in the lab. The samples were prepared according to different grain size distribution, degree of saturation and earthquake magnitudes. The relations of dynamic shear strength, degree of saturation, and number of cycles are summarized through analyzing experimental results. The findings show that the gravelly soil with a wide and continuous gradation has a critical degree of saturation of approximately 87%, above which debris flows will be triggered by rainfall, while the debris flow will be triggered at a critical degree of saturation of about 73% under the effect of rainfall and earthquake(M>6.5). Debris flow initiation is developed in the humidification process, and the earthquake provides energy for triggering debris flows. Debris flows are more likely to be triggered at the relatively low saturation under dynamic loading than under static loading. The resistance of debris flow triggering relies more on internal frication angle than soil cohesion under the effect of rainfall and earthquake. The conclusions provide an experimental analysis method for dynamic initiation mechanism of debris flows. 相似文献
17.
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????2006??7??4???????5.1?????????????????λ???仯????,??????1970???????????????????????????????:1)2000??????????NNE???????????,?????????????????????NEE????;2)???????????????????????????????????????,????????????????????ε???;3)????????????NE???????????仯???,??????仯?????????С??????????????? 相似文献
18.
The construction of a high-speed railway (HSR) in Southwest China is being hindered by a severe shortage of high-quality subgrade materials. However, red mudstone is widely distributed in the Sichuan Basin of China. The ability to use weathered red mudstone (WRM) to fill subgrade beds by controlling its critical stress and cumulative strain would enable substantial savings in project investments and mitigate damage to the ecological environment. To better understand the dynamic behaviour of WRM, both monotonic and cyclic triaxial tests were performed. The evolution of the cumulative strain vs. increased loading cycles was measured. The influences of confining pressure and loading cycles on the dynamic modulus, damping ratio, critical cyclic stress ratio (CSR), and dynamic stress level (DSL) were investigated. The relationship between the CSR and loading cycles under different failure strain criteria (0.1%-1.0%) was analysed. The prediction model of cumulative strain was also evaluated. The results indicated that the shear strength of WRM sufficiently meets the static strength requirements of subgrade. The critical dynamic stress of WRM can thus satisfy the dynamic stress-bearing requirement of the HSR subgrade. The critical CSR decreases and displays a power function with increasing confining pressure. As the confining pressure increases, the DSL remains relatively stable, ranging between 0.153 and 0.163. Furthermore, the relationship between the dynamic strength and loading cycles required to cause failure was established. Finally, a newly developed model for determining cumulative strain was established. A prediction exercise showed that the model is in good agreement with the experimental data. 相似文献
19.
研究不同环剪条件下库岸堆积层滑坡滑带土强度特性对滑坡稳定性评价具有重要意义。针对目前在库岸堆积层滑坡滑带土力学特性方面研究薄弱的问题, 以三峡库区童家坪滑坡滑带土为研究对象, 采用ARS-E2环剪仪开展了不同剪切速率下的剪切试验, 研究了等速剪切、加速剪切以及减速剪切作用下滑带土强度变化特征。试验结果表明: 滑带土试样在恒定的低速剪切条件下更容易得到稳定的残余强度, 并且达到峰值强度后易出现"应变软化"现象; 在相同剪切应力条件下, 滑带土加速环剪和减速环剪的剪应力变化趋势基本一致, 与法向应力均呈正相关关系; 剪切速率的变化会显著影响滑带土峰值黏聚力的大小。研究成果揭示了不同环剪条件下滑带土力学特性, 可以为揭示库岸堆积层滑坡变形破坏的力学机制提供理论依据。 相似文献