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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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针对黄土地区实现工程施工材料本土化和科学利用粉煤灰问题,对不同配比条件下粉煤灰改性黄土进行重塑非饱和试件的动三轴震陷试验,研究其在动荷载作用下的震陷特性,分析粉煤灰掺入量对动变形模量和动残余应变的影响变化规律。研究结果表明:粉煤灰掺入量对黄土震陷性质的影响较大。相同固结应力水平下,动变形模量和动残余应变随粉煤灰掺入量呈现出不同的变化规律,随着粉煤灰掺入量的增加,黄土动变形模量也随之增大,残余应变则减小。动变形模量与动残余应变之间的变化趋势满足幂函数关系;黄土掺加约20%粉煤灰改性后就能够有良好的抗震陷性能。研究成果可为黄土地区地基的抗震防震设计提供借鉴依据,具有重要的工程实用价值。 相似文献
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基于动三轴试验和SEM细观结构测试试验,结合图像分析处理软件,对强震荷载前后宝兰客运专线沿线典型震陷性黄土及其经物理、化学和复合改良方法处理后的试样进行微观尺度的结构变形演化规律研究,探讨不同改良方法对土体微结构的影响及其与震陷系数之间的内在联系。结果表明:(1)物理改良方法对于消除大孔隙和架空孔隙结构的效果最为明显,同时对颗粒级配和结构也有调整;(2)化学改性方法则从颗粒接触方式、粒间胶结程度等方面影响土体强度,且不同化学反应的参与可生成独特的玻璃微珠或絮凝状细结构,从而大大提升土体某项参数指标,进而在强震中分别起到填充、胶结或缓冲作用;(3)强震作用前后不同改良方法对各微观要素的改变与相应的残余应变现象吻合较好,说明微结构能有效反映改良黄土残余变形的强弱。 相似文献
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采用中国地震局工程力学研究所研制的DSZ-Ⅰ型电磁振动三轴仪对大连临空产业园工程场地的土样（浅层砂和深层砂）进行动力特性试验,研究两种砂土在复杂应力状态下的动力残余变形特性。试验结果表明：残余体应变和残余剪应变都随着动应力比和围压的提高而增大,动应力比和围压的影响对残余体应变和残余剪应变的影响规律是一样的;残余体应变随着固结比的提高而减小,而残余剪应变随着固结比的提高而增大,残余体应变的固结比对于试验结果与拟合结果的影响较大,而残余剪应变固结比对于试验结果与拟合结果的影响较小;残余体应变和残余剪应变的Cvr与动应变幅值较好满足线性关系,离散性非常小,而Cdr/S21与动应变幅值关系的离散性则比较大。并给出了地基震陷分析所需的沈珠江模型参数。研究成果可为大连临空产业园填海造地工程抗震设计和地基震陷变形分析提供依据,也可作为其它类似填海造地工程的设计参考。 相似文献
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采用中国地震局工程力学研究所研制的DSZ-Ⅰ型电磁振动三轴仪对大连临空产业园工程场地的土样（浅层砂和深层砂）进行动力特性试验，研究两种砂土在复杂应力状态下的动力残余变形特性。试验结果表明：残余体应变和残余剪应变都随着动应力比和围压的提高而增大，动应力比和围压的影响对残余体应变和残余剪应变的影响规律是一样的；残余体应变随着固结比的提高而减小，而残余剪应变随着固结比的提高而增大,残余体应变的固结比对于试验结果与拟合结果的影响较大，而残余剪应变固结比对于试验结果与拟合结果的影响较小；残余体应变和残余剪应变的Cvr与动应变幅值较好满足线性关系，离散性非常小，而Cdr/S21与动应变幅值关系的离散性则比较大。并给出了地基震陷分析所需的沈珠江模型参数。研究成果可为大连临空产业园填海造地工程抗震设计和地基震陷变形分析提供依据，也可作为其它类似填海造地工程的设计参考。 相似文献
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黄土震陷是常见的地震灾害。历史地震中,黄土震陷常有发生并导致地基沉降、诱发滑坡并造成生命财产损失。通过室内试验研究黄土动荷载残余变形,分析不同因素对黄土震陷的影响,揭示黄土震陷的发生机理,这对于准确评价黄土场地震陷性, 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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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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Xiaowu Pu Lanming Wang Ping Wang Xiufeng Tian Shiyang Xu Shaofeng Chai Haitao Guo 《地震研究进展（英文）》2022,2(3):100114
A series of housing collapses and other serious damage was caused by the 2008 Wenchuan MS 8.0 earthquake in the seismic intensity Ⅵ areas of the Loess Plateau, which is hundreds of kilometers away from the epicenter, and which showed a remarkable seismic intensity anomaly. The seismic disasters are closely related to the seismic response characteristics of the site, therefore, the systematic study of the far-field seismic response law of the Wenchuan earthquake in the Loess Plateau is of great significance to prevent the far-field disaster of great earthquake. In this paper, the seismic acceleration records of several bedrock stations and loess stations from the seismogenic fault of the Wenchuan earthquake to the Loess Plateau were collected, and the attenuation law of ground motion along the propagation path and the characteristics of seismic response on the loess site are studied, and the mechanism of amplification effect of ground motion is analyzed based on the dynamic feature parameters of the loess site obtained through the HVSR method. Taking a typical loess site of thick deposit as the prototype, a series of shaking table tests of dynamic response of loess site models with different thicknesses were carried out. Amplification effect, spectral characteristics of acceleration in model sites were analyzed under the action of a far-field seismic wave of the Wenchuan earthquake. The results show that seismic attenuation on the propagation path along the NE strike of the seismogenic fault to the Loess Plateau is slower than that in other directions, and the predominant period range of ground motion on bedrock site of the Loess Plateau presents broadband characteristics. Because the natural periods of loess sites with thick deposits are within the predominant period range of bedrock input wave, loess sites appear significant amplification effect of ground motion, the horizontal acceleration of ground motion exceeds 0.1 ?g, the seismic intensity reaches 7°. The thicker the loess deposit is, the more significant the change of spectral characteristics of ground motion on loess sites, and the narrower the predominant period range of ground motion becomes, and the closer it is to the natural period of loess sites. Therefore, for some old houses on thick loess sites, the poor seismic performance and strong seismic response eventually led to their collapses and damages because their natural periods are very close to the predominant period of ground motion of the Wenchuan earthquake on thick loess sites; For these damaged high-rise buildings, the resonance effect might be the main reason for their damages because their natural periods are included in the predominant period range of ground motion of the Wenchuan earthquake on thick loess sites.These research results would provide a basis for seismic disasters prediction and evaluation and seismic design of construction engineering in the Loess Plateau. 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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土体动力特性主要与其受力状态、土体加载类型、试验控制方式以及荷载等参数有关。以往非饱和黄土累积变形试验研究通过单向动应力加载方式开展相关研究,并不能真实反映土体受力状态。现运用WF-12440型动三轴-空心圆柱扭剪试验系统,通过单向荷载和双向荷载两种不同的动应力加载方式,进行黄土的长期重复载荷试验,对比不同动应力加载方式对非饱和黄土累积变形发展特征的影响。试验结果发现：黄土在单向荷载或双向荷载作用下,其软化指数均随着循环次数的增加,呈非线性减小的趋势,在相同循环振次时,土体软化指数随着动应力幅值的增大而减小;黄土在不同加载方式作用下,软化指数减小速率在循环振次100次以内较快,后期随振次增加,土体软化速率逐渐趋于平稳;黄土在双向荷载作用下,当轴向动荷载较小时,径向荷载的施加,将加速黄土的软化程度,随着轴向动荷载的增大,径向荷载对黄土软化的影响逐渐减弱,其对于黄土变形的影响存在一临界轴向循环动应力。本研究的开展,可更准确地进行不同荷载耦合变化下,黄土场地震陷评估或路基土体变形计算,实现有效控制路基的整体稳定和工后沉降量,以期根据路基土参数预测后期沉降,极具重要的科研和工程意义。 相似文献
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基于FLAC3D数值模拟方法,建立不同类型的黄土场地计算模型,研究地震动强度和频率对不同类型黄土场地的动力响应特征和变形规律,分析不同类型黄土场地地震动响应的差异性,揭示不同类型黄土场地诱发的地震灾害,结合理论分析验证数值模拟结果的可靠性。研究表明:黄土-泥岩接触型二元结构斜坡极易发生滑动破坏引起斜坡失稳,并且在坡肩位置引起较为明显的动力响应,加速度放大系数是坡顶的2倍左右,是一元结构黄土斜坡相同部位加速度放大系数的1.5倍左右; 黄土斜坡临空面的存在会引起土体沿坡面发生一定范围的滑动和堆积,黄土塬内较塬边更为稳定,不易发生损伤破坏; 低频地震波对平坦场地的地震响应影响明显,随着高程的增加,频带宽度增加,傅里叶谱幅值增加,坡肩处的幅值是坡脚的2倍左右; 黄土斜坡场地易诱发大面积的滑坡灾害,黄土塬场地在剪切力和压张破坏条件下易诱发局部震陷灾害。 相似文献