共查询到19条相似文献，搜索用时 281 毫秒
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饱和粉土液化和应变特性试验研究 总被引：3，自引：0，他引：3
对取自徐州市棠张镇拟建京沪高速铁路路基的粉土,在试验室内按不同的干密度和细粒含量进行重塑,完成了三组不同干密度和四组不同细粒含量的振动三轴液化试验。分析了粉土干密度和细粒含量对饱和粉土抗液化强度的影响;通过曲线拟合方法建议了粉土振动液化过程中的孔压增长模型和永久应变势模型,给出了模型参数。 相似文献
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针对荆江大堤江陵段下伏地层广泛分布的饱和粉细砂,参照原位试验成果重塑粉细砂试样,按估算的固结应力比(Kc约为1.6)对试样动剪模量、阻尼比及总应力动强度进行测试,结果表明:(1)试样应力-应变骨干曲线与Hardin-Drnevich双曲线模型假设高度吻合,Hardin公式可很好地拟合动模量/阻尼比与动应变的关系。在研究试样密实度范围内,最大动模量随围压和密实度的增加而增加,但围压对动模量的敏感性更高,且相同围压下动剪模量比与动应变关系曲线近乎重合。围压增大或密实度升高均会引起阻尼比的降低,1%应变对应的阻尼比分布在0.15~0.21之间;(2)偏压状态下以累积轴向应变5%作为液化判别标准进行抗液化强度试验,随特征振次及测试围压的增大,液化动剪应力比相应减小,试样振动孔压比最高仅能达到0.8~0.9;(3)由总应力法求取的动内摩擦角与黏聚力均随设定特征振次的增加而下降,且内聚力并非约等于0,表明动力作用下该试样具有一定的黏滞性。 相似文献
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地震荷载作用下黄土的孔压增长特性、模型及参数是黄土场地液化评价的关键。文章以甘肃庆阳董志塬地区黄土为研究对象，通过不同土性和荷载条件下饱和重塑黄土的液化试验，对黄土的液化特征、典型孔压模型的适用性及参数的取值范围进行研究。研究表明动荷载作用下饱和重塑黄土孔压增长曲线主要分为三类，通过对比验证不同孔压模型对饱和重塑黄土孔压增长曲线的适用性，给出了适用性较好的孔压模型的参数取值范围，其中，Seed模型的参数α取值范围为1.09～1.84,A型曲线模型参数β取值范围为1.70～2.52,幂函数模型参数θ取值范围为1.13～1.75。根据陇西黄土孔压曲线对模型进行验证，结果表明模型的参数取值范围具有区域性，对于陇西黄土，Seed模型、A型曲线模型和幂函数模型的拟合参数取值分别为0.91、8.32和3.51。 相似文献
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利用多功能动三轴仪的先进功能,对3%、6%、8%、9%、12%和15%黏粒含量的粉土进行了动三轴试验。试样在初始液化后继续施加动荷载,达到不同的双幅轴向应变后施加不排水单调荷载模拟液化后大变形。研究结果表明,相同循环周数时不同黏粒含量对动加载阶段的动剪应力影响规律与其对液化后初始阶段大应变规律有内在联系,即黏粒含量为8%时动剪应力最小而液化后低强度段应变最大,而强度恢复段模量也最低。试验验证结果表明,拟合关系式能较好地反映不同黏粒含量粉土液化后大变形。 相似文献
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Laboratory tests on the large post-liquefaction deformation of saturated Nanjing fine sand were performed by using a hollow cylinder apparatus. The stress-strain responses and the characteristics of excess pore water pressure after liquefaction were studied. It was found that the relationship between deviatoric stress and axial strain presented a sigmoid curve, and there was a good linearity relationship between normalized pore water pressure and deviatoric stress. On this basis, a constitutive model of stress-strain responses and a dissipation model of excess pore water pressure were established. It was found that the results predicted by the two models were in good agreement with the experimental data. The influence of relative densities and confi ning pressure on the characteristics of liquef ied soil were studied. The results showed the relative densities and initial effective confining pressure all had an important influence on the stress-strain responses of liquefi ed saturated Nanjing fine sand. However, the dissipation model of excess pore water pressure after liquefaction was only affected by the confining pressure. 相似文献
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为研究1920年海原地震中石碑塬地区液化滑移灾害的形成机制、滑移特征及滑移距离，对石碑塬液化滑移区进行钻孔勘探、取样以及探槽开挖。分别对钻孔及所取试样进行剪切波速测试及颗粒分析、室内动三轴试验，得出石碑塬液化滑移区地层分布情况、震时液化土体层位以及不同地震烈度条件下砂质黄土层的液化情况。综合分析钻孔勘探、颗粒分析、动三轴试验结果，揭示出海原地震中石碑塬黄土地层液化滑移灾害的形成机制：砂质黄土层液化后在自重应力以及地震力的共同作用下"托浮"第一古土壤层以及上部"粉尘化"的非饱和黄土层沿缓斜坡运动，并利用液化滑移地层滑距公式对滑移距离进行估算，得到结果为223.35 m，与实际情况较为相符。研究结果可为黄土地层液化滑移灾害的预防提供一定的借鉴意义。 相似文献
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利用全自动多功能三轴仪进行了粉土场地的液化后变形试验,探讨了粉粒含量对液化后应力应变关系的影响.试验时施加动加载使试样达到设定的液化程度,然后立即施加单调荷载,以模拟地震现场发生强震时初始液化到液化后变形的整个过程.研究发现,不同粉粒含量粉土场地发生液化后变形得到的液化后应力应变关系可采用推导的同一理论关系式表示,其系数的差异表明了粉粒含量对粉土液化后变形的影响.验证结果表明该关系式能较好地模拟粉粒含量对粉土场地液化后应力-应变的影响,为同一地区或相似地区粉粒含量变化的粉土场地液化评估提供依据. 相似文献
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为了经济、环保地达到改良处理减轻饱和黄土地基液化震害的目的,通过配备不同粉煤灰掺量的改良黄土进行动三轴试验,研究饱和粉煤灰改良黄土的动应力、动应变和动孔隙水压力变化特征,分析粉煤灰掺量对饱和改良黄土液化应力比、动残余变形和动孔隙水压力的影响规律,并结合微结构试验结果,探讨饱和粉煤灰改良黄土抗液化的物理化学机制。结果表明:粉煤灰掺量对饱和改良黄土的液化应力比、动应变和动孔隙水压力比均具有较为显著的影响。随着粉煤灰掺量的增加,饱和改良黄土的液化应力比持续增加,且当掺量达到15%后,继续增加粉煤灰掺量时改良黄土的液化应力比增加显著。饱和改良黄土的动应变和动孔隙水压力比均随着粉煤灰掺量的增加而减小;掺量达到25%后,饱和改良黄土不液化。饱和粉煤灰改良黄土的SEM细观结构试验照片中呈现大量的圆球状、粒状粉煤灰颗粒和絮凝状胶结物,表明其抗液化的物理化学机制主要包括粉煤灰的水化作用、胶体生成物和颗粒的填隙作用和粉煤灰对游离水的吸附作用。 相似文献
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黄土具有极强的水敏性和动力易损性，黄土地区多次强震都引起过液化、滑坡等地质灾害，造成了严重的人员伤亡和财产损失，因此振动作用下高含水率黄土的液化问题不容忽视。在大量已有研究的基础上，以宁夏党家岔滑坡为例，研究振动作用下高含水率黄土的液化问题。现场调查发现高含水率滑带土并未达到完全饱和状态（饱和度达95%左右），在新鲜的芯样断面发现有明显的"流态化"液化破坏特征。借助室内试验和数值模拟技术，对党家岔滑坡非饱和黄土层的液化性能及液化发生机理进行分析。结果表明：（1）非饱和黄土层液化发生机理可概括为：地震作用下饱和黄土层孔隙水压力激增，高含水率非饱和黄土层孔压增长响应滞后，随着孔隙水压朝上部消散，地下水向上渗流，当平均有效应力接近0时，高含水率非饱和黄土层发生液化；（2）振动过程中不同饱和度黄土孔隙水压力增长响应具有滞后性，借鉴饱和黄土液化时孔压比的判别标准和Seed简化判别法，初步证实党家岔滑坡高含水率非饱和黄土层可发生振动液化，斜坡前缘和中部土体发生液化的初始饱和度范围分别为68.3%~100%和73.8%~100%，斜坡后缘土体不发生液化。 相似文献
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To understand the post-liquefaction behavior of liquefied ground, it is important to get a better understanding and a more suitable characterization of the variation of excess pore pressure after liquefaction. In this paper, the soil permeability is considered as one of the key soil parameters for clarifying the mechanism of post-liquefaction behavior of liquefied ground. For this reason, a series of shaking table tests were conducted for a Toyoura sand deposit with different soil permeability values. Polymer fluid was used in model tests to vary the permeability of sand deposits. Excess pore pressures and settlements were measured in each test. A basic mechanism in post-liquefaction behavior and the solidification phenomenon after liquefaction were discussed based on these test results. Also, a new method for predicting the dissipation of excess pore pressure was developed. This study provides evidence of the important effect of soil permeability on the velocity with which the solidification front moves upward in liquefied ground. It is suggested that the value of coefficient of permeability of liquefied sand can increase to about 4.0 times the initial value. This variation of permeability after liquefaction should be taken into account in post-liquefaction analysis. 相似文献
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MA Xingyu WANG Lanmin WANG Qian WANG Ping ZHONG Xiumei PU Xiaowu LIU Fuqiang XU Xiaowei 《中国地震研究》2020,34(4):469-481
Based on the dynamic triaxial liquefaction test of the loess samples which are taken from Shibei tableland, Guyuan City, Ningxia, China, the characteristics of dynamic strain, dynamic stress and pore water pressure are studied under cyclic loading. Triaxial shear test is conducted immediately after the sample reaches liquefaction point. During the test, the property of the liquefied soil is analyzed through fluid mechanics method, whereby the fluidity of the liquefied soil is represented by apparent viscosity.The results show that the fluidity of liquefied loess changes from "shear thickening" to "shear thinning" as the shear force continues, and the fluidity of liquefied loess is closely related to its structure. In addition, in the process of forming a new stable state, the apparent viscosity and deviant stress change with axial strain in a similar approach. When the sample reaches its stable state, it meanwhile shows a relatively stable apparent viscosity. According to the fluid mechanics and the law of conservation of energy, the slip distance of the liquefied soil is estimated, and the results are in good agreement with the field investigation results. 相似文献
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Mitsutoshi Yoshimine Hiroto Nishizaki Kei Amano Yasuyo Hosono 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):253-264
This paper intended to evaluate the behavior of saturated sand and sloped ground subjected to flow failure with seepage of pore water in the ground after earthquake and the resultant liquefaction. Triaxial compression tests of sand with constant deviator stress but changing of pore pressure and volume of the specimens were conducted in this study. It was revealed that the relation between the volume change and the amount of shear strain during deformation depended on the initial density of the sand but it did not much depend on shear stress and initial confining stress levels. Based on this test results and numerical analysis of the seepage of pore water in liquefied ground, a methodology was proposed to predict the deformation of inclined ground due to liquefaction. 相似文献
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为进一步认识固化黄土的力学特性，以郑州地区黄土为试验材料，制备不同固化剂掺量的试样，并在标准养护条件下养护至试验龄期后饱和。应用GDSTTS标准应力路径三轴仪，开展固结不排水(CU)剪切试验，主要研究围压、固化剂掺量以及养护龄期对固化黄土力学特性的影响。试验结果表明：郑州地区固化黄土具有显著的结构性，其应力应变曲线呈现出应变软化特征，并可用驼峰型三参数表达式描述；同时，增大围压和固化剂掺量以及延长养护龄期，固化黄土的峰值应力及残余应力都增大、养护龄期超过一定时间后，其对固化黄土强度的影响趋弱。 相似文献