共查询到18条相似文献，搜索用时 203 毫秒
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地震荷载作用下黄土地基震陷研究 总被引：1，自引：0，他引：1
在某大型企业的地震安全性评价工作中，采用随机地震荷载输入动三轴进行了黄土震陷试验，探讨了该场地黄土在不同动荷载作用下的震陷特性。并对该场地地基未来可能发生的震陷灾害进行了评价，为工程地基抗震处理提供了依据。 相似文献
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本文以1995年甘肃省境内5．8级地震引起的黄土地区震陷灾害实例，对黄土微结构孔隙性进行了定量研究。通过电镜扫描手段和SEM图像处理技术，对极震区震陷性黄土微观结构的各项指标进行了比较分析，得出不同地点的黄土孔隙分布曲线；对极震区受地震破坏和未受破坏典型架空孔隙结构的黄土进行了定量处理，较好地解释了土体的工程性质，结合激光粒度分析仪对极震区黄土进行了测量和统计分析。同时对无震区与强震区黄土孔隙分布曲线进行了对比研究。结果表明：不同极震区的孔隙分布特征不同，同一深度不同区域孔隙分布曲线亦有明显的差异。 相似文献
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永登5.8级地震极震区黄土微结构孔隙性的定量研究 总被引：1，自引：0，他引：1
通过电镜扫描手段和计算机图像处理,对1995年永登5．8级地震极震区遭受地震影响和未遭受地震影响的黄土微结构变化的各项指标进行了对比试验和分析,并将分析结果绘成受震与未受震两种孔隙分布曲线。从这些曲线可以看出,不同地点的黄土孔隙分布特征不同;同一深度不同地点的孔隙分布亦有明显差异。对未受震(粒状架空孔隙结构)与受震(粒状镶嵌孔隙结构)黄土的微观结构进行了定量处理,其分析结果较好地解释了土体的工程性质。同时介绍了黄土微结构研究的方法和要求,通过对黄土微观结构的定量处理,揭示了黄土震陷性与黄土孔隙含量所占比例大小的内在关系,达到了确定黄土场地震陷量的目的,验证了利用微结构研究黄土结构变化的可行性。 相似文献
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黄土在我国西北地区广泛分布,而其动力特性迄今很少了解。为了编制兰州市区场地抗震区划图,我们对市区黄土的动力性质进行了初步实验研究。共采集了8个样品,用动力三轴仪进行了实验。项目包括动荷作用下的弹性模量、阻尼、强度与震陷,计完成了22项次,本文就是此次实验结果的小结。 相似文献
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为了研究地震荷载作用下黄土场地的震陷预测问题,以兰州黄土为研究对象来分析剪切波速和含水率与震陷系数的关系,并分别得出拟合函数关系。通过分析剪切波速和含水率在震陷过程中的内在联系,建立剪切波速和含水率双指标预测黄土震陷系数的方法,并依据该方法预测永登地震区黄土场地震陷量。研究结果表明:在一定的剪切波速区间内,震陷系数随着含水率的增加而增大;在一定的含水率区间内,震陷系数随着剪切波速的增加而减小。同时提出剪切波速可以反映黄土不因外部条件而变化的潜在震陷能力为绝对震陷能力的概念,相应的震陷系数称为绝对震陷系数,含水率影响潜在震陷能力的释放。通过震害实例计算验证剪切波速和含水率双指标预测方法的可行性。 相似文献
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Lanmin Wang Junjie Sun Xuefeng Huang Shunhua Xu Yucheng Shi Rendong Qiu Zhenzhong Zhang 《Soil Dynamics and Earthquake Engineering》2011
At present piles foundation is widely used in the earthquake-prone loess area of China. Unfortunately, negative skin friction (NSF) along piles induced by an abrupt settlement of loess under strong earthquakes, so called seismic subsidence, has not been taken into account in design of piles foundation due to the lack of NSF data from field test. In order to investigate NSF along piles caused by seismic subsidence of loess and develop a method to estimate this earthquake-induced NSF, the authors perform a field test at a loess site by means of a series of explosions, i.e. a short delay blasting, in which two reinforced concrete piles was grouted. The expected ground motion generated by the short delay blasting is strong enough to induce an obvious seismic subsidence in the loess site. There are 40 stress gages to be averagely disposed into the two piles with a certain interval to collect the data of NSF during this field test. Meanwhile, ground motion and seismic subsidence of loess were, respectively, observed by accelerographes and a level gauge. The obtained data particularly disclose the developing characteristics and magnitude of loess seismic subsidence and NSF at the condition of strong ground motion. The loess seismic subsidence and NSF both have a rapid development in the explosion process and then keep a slower increase for some days after the blasting. At the end of observation, the maximum seismic subsidence of loess in the field reaches 33 mm; the average NSF along piles attains to 54 kPa, which is much greater than previous cases of NSF caused by collapse of loess. This field test shows the NSF along piles induced by seismic subsidence of loess is significant and should not be ignored in design of piles foundation in seismic loess regions. 相似文献
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Experimental study on the influence of seismic subsidence of loess under bidirectional loading modes
《地震研究进展（英文）》2021,1(4):100064
Water content, dry density, void ratio, depth of soil layer, and seismic loading may all exert influence on the seismic subsidence of loess. Many scholars have carried out seismic subsidence tests of loess to simulate the stress on soil using unidirectional (axial) vibration instead of bidirectional vibration. We conduct seismic subsidence tests of loess using two different dynamic stress loading methods, unidirectional and bidirectional dynamic stress. In addition, the effects of different dynamic stress loading modes on the development of seismic subsidence of loess are compared for a case-study in northwestern China. The results show that (1) the increasing ratio of radial stress to axial stress has exerted significant influence on the seismic subsidence coefficient of loess under the loading mode of bidirectional dynamic stress (2) there is a critical ratio of radial stress to axial stress for seismic subsidence of loess, ranging from 0.6 to 0.8; when the ratio of radial load to axial load is greater than the critical value, the effect of bidirectional load on the development of seismic subsidence is more remarkable (3) when the ratio of radial load to axial load is smaller, the seismic subsidence of loess calculated by the existing unidirectional stress loading method is safe for engineering projects. However, if the value exceeds the safety ratio range it is dangerous to conduct safety evaluations using the seismic loess subsidence. The prediction value of seismic subsidence at engineering sites directly affects the later foundation treatment and the safety of the overlying structures. The seismic subsidence calculation and evaluation method in this study may provide a scientific basis for safety evaluations of loess sites in northwestern China. 相似文献
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非饱和黄土震陷物理力学机制与主导影响因素 总被引：1，自引：0，他引：1
通过分析黄土震陷的物理过程及其力学机制,指出非饱和黄土震陷实质上是土体广义固相介质响应外部动荷载作用的再固结过程。将影响黄土震陷的主导因素归纳为两方面,即土体广义固相介质的强度、体积特征和外部动荷载特征。介质的强度特征可通过引入土工试验获取的参数(粘聚力和内摩擦角)来宏观表征;体积特征可由能够反映土体欠压密程度的孔隙比描述。与非饱和黄土震陷的宏观物理力学机制相适应,粘聚力与内摩擦角主要反映土体的结构性强度(黄土强度特征),孔隙比则反映了土体再固结的潜在性态(黄土沉降量值特征);黄土强度特征对应土体抵御外部载荷的能力,黄土沉降量值特征对应外部载荷作用下的土体沉降能力。 相似文献