【作者】 邓学晶；

【导师】 孔宪京；

【作者基本信息】 大连理工大学 ， 岩土工程， 2007， 博士

【摘要】 城市垃圾填埋场的地震稳定性评价是环境岩土工程领域遇到的新问题。鉴于目前对其地震变形机理缺乏深入的了解、工程设计中仍沿用传统土力学边坡稳定分析方法的研究现状，本文结合国家自然科学基金重点项目(50538080)“城市垃圾填埋场固、液、气相互作用及土力学机理”中的第4子题“垃圾填埋场动力稳定机理及分析方法”，利用振动台模型试验技术，在垃圾填埋场地震破坏机理分析的基础上进行理论研究，尝试建立适合城市垃圾填埋场结构特点的地震稳定性分析方法。论文主要内容如下：1．针对城市垃圾填埋场的结构形式设计8个缩尺模型，进行振动台模型试验，通过对比分析一系列的试验现象，揭示了地震作用下填埋场的几个响应规律：(1)沿填埋场底部衬垫层和顶部覆盖层的接触面发生较大相对滑移，是地震作用下现代城市垃圾填埋场的主要破坏模式，其中观察到的覆盖层破坏现象能够印证Ling，H．I．提出的“双滑楔体”假定，垃圾堆体内部不容易出现明显的滑动面；(2)填埋场防渗层的永久位移与振动台台面的水平最大位移近似成比例；(3)填埋场衬垫层土工膜能够减弱地震能量向上部结构的传递，输入地震动的加速度峰值越大，减弱的效果越明显。2．对振动台试验中的模型填埋场进行非线性数值模拟，目的是补充验证振动台试验的主要结论，以及为验证本文第四、五章的填埋场地震稳定性评价方法做准备。3．假定沿填埋场底部衬垫层的潜在滑动体由三个刚性滑块组成，对基础具有一定坡角的填埋场进行极限平衡分析，推导了衬垫层屈服加速度系数的计算公式，采用非线性数值计算和振动台试验结果对公式进行了验证；在填埋场地震破坏机理分析的基础上，定义了填埋场覆盖层和衬垫层的水平等效加速度(时程)HEA_c(t)和HEA_d(t)，通过二维非线性数值计算，说明了以覆盖层和衬垫层的最大水平等效加速度MHEA_c和MHEA_d代表地震在防渗层引起的荷载水平，评价填埋场的地震稳定性具有客观合理性；给出对填埋场防渗层的地震稳定性进行2D拟静力分析的步骤。4．对具有摩擦型接触面的NewMark双滑块系统进行能量分析，建立NewMark双滑块模型的能量守恒方程，理论分析得到，谐振激励下接触面发生最大相对滑移量时对应的能量系数e与(K_y／K_a)~2存在近似线性关系：利用这一关系对真实地震波作用下地震永久位移的计算结果进行统计分析，给出了地震永久位移的简化计算公式；将简化计算公式与其它学者建议的计算公式进行对比、以及算例表明，本文的公式计算结果合理、具有简单的形式、便于工程应用。5．对具有典型几何构型的填埋场进行二维分析，以考察填埋场的地震响应特性，研究垃圾土初始剪切波速、填埋场高度、场地条件、输入地震动频谱特性等参数对填埋场顶部加速度响应的影响；作为本文研究成果的工程应用实例，分别以最大水平等效加速度MHEA_d和MHEA_c代表填埋场基底衬垫层和覆盖层的地震荷载水平，评价了填埋场的地震稳定性；针对最危险工况，采用本文建议的公式(5.29)和(5.30)，计算了地震作用下填埋场衬垫层和覆盖层的永久位移。6．对复杂荷载条件下填埋场防渗层HDPE土工膜的受力状况进行了非线性数值模拟，得到的主要结论有：土工膜内的拉应力随着垃圾土分层填埋、基础不均匀沉降、地震荷载的作用而积累，基础不均匀沉陷是影响衬垫层土工膜局部拉应力的主要因素，中等强度地震动输入可使覆盖层土工膜锚固位置的拉应力超过极限拉应力。更多还原

【Abstract】 Seismic stability evaluation of municipal waste landfill is a new challenge in environmental geotechnology. Due to lack of understanding seismically induced deformation mechanism, seismic stability analyses of landfills are commonly performed using the methods developed to analyze earth embankments. Physical model experiments of landfill are conducted on shaking table in this thesis, then, based on analyzing earthquake failure mechanism of landfills, theoretical studies are performed, in order to develop the special methods for seismic stability evaluations of landfills.The main research results of are as followed:1. According to the typical landfill configuration, 8 physical models are designed, and the following conclusions are drawn from shaking table test:(1) Experiencing excessive relative displacement within the specific interfaces of landfill liner and cover systems is the primary observed failure patterns induced by earthquake, however, waste itself collapse is seldom a concern problem.(2) When other parameters are fixed, seismically induced permanent displacement of landfill liner are shown to be approximately proportional to the amplitude of input motion.(3) Significant acceleration attenuation of motion took place when earthquake wave transfer through landfill base liner which including HDPE geomembrane, moreover, the attenuation is more obvious, while the peak acceleration of input motion is larger.2. Nonlinear numerical simulation of Landfill models using in shaking table test is conducted, in order to supplement verification of the physical model test results and be prepared to validate the proposed stability evaluation method.3. On supposing that the potential sliding mass above landfill base liner are constituted of three rigid blocks, a formulation, to estimate the yield acceleration of landfill base liner approximately, is presented by limit equilibrium analysis. Based on analyzing seismically induced deformation mechanism of landfills, the Horizontal Equivalent Acceleration (time-history) HEA_c(t) and MHEA_d(t) are defined at landfill top cover slop and base liner respectively. Nonlinear numerical calculation of the landfill models indicates that the Maximum Horizontal Equivalent Acceleration MHEA_c and MHEA_d can represent the loading level induced by earthquake. The process of pseudo-static analysis to evaluate the earthquake stability of 2D landfill is given. 4. Energy dissipation and transfer of frictional slip surface between two rigid blocks are investigated; then, an energy balance equation is formulated for NewMark sliding-block model. Theoretically, an approximate linear relationship between the energy coefficient e vs (ky/ka)~2 is found when the relative displacement in the interface get the maximum value with sine wave input. Considering the approximate linear relationship, statistical analysis of earthquake-induced permanent displacement data, which are results from. NewMark sliding-block model numerical calculation, is conducted, and a Simplified formulation for predicting the earthquake-induced displacement of landfill is presented, Comparison with other earthquake-induced permanent displacement fomulas in literature indicates that calculating results using the proposed formulation is reasonable, and can be used in practice more easily.5. 2D seismic response of landfills with typical geometry configuration is explored in detail, in order to investigate seismic response characteristics of landfills, as well as to study how the factors, including wastes properties, landfill heights, input motion and site conditions, to influence top acceleration response of landfills. With the Maximum Horizontal Equivalent Acceleration (MHEA_d and MHEA_c) representing the loading induced by earthquake in landfill deep liner system and cover system respectively, the stability of landfill is evaluated. As an engineering application example of the formulation (5.29) and (5.30) suggested in this thesis, the permanent displacement induced by earthquake of the most dangerous case.6. A finite difference analysis using the computer code FLAC is conducted of tension in landfill HDPE geotechnical membrane under complicated loads. The main conclusions are: (1)the accumulative tensile stress is developed in HDPE membrane by waste dumping, differential settlement, and earthquake. (2) the differential settlement effects the stress in liner HDPE membrane primarily. (3) the tensile stress in cover system HDPE membrane is higher than ultimate strength of HDPE geotechnical membrane under moderate intensity motion input (eg peak acceleration is 0.25g)更多还原