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1.
扩建城市垃圾填埋场的地震稳定性分析 总被引:1,自引:0,他引:1
结合现场剪切波速试验、室内常规及动三轴试验结果,给出了扩建城市垃圾填埋场地震稳定性的有限元分析方法,并分析了扩建垃圾填埋体沿填埋体内部圆弧滑动面、新老填埋体交界面及底部和背部衬垫系统的地震稳定性。当填埋场中渗滤液水头较低时,扩建填埋体最易发生沿新老填埋体交界面的滑动。与总应力法计算结果相比较发现,总应力法只适合分析输入地震动较小的情况,而当输入地震动较大时,由于它不能考虑动孔压上升所导致的MSW软化而使得其计算的扩建填埋体沿圆弧滑动面的安全系数偏保守。另外,采用Newmark法分析了不同输入地震动时不同横、竖向扩建方案的永久位移,分析表明:扩建填埋体沿新老填埋体交界面的地震永久位移的对数近似与屈服加速度同最大水平加速度的比值呈线性关系,并给出了其永久位移的拟合公式。 相似文献
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3.
《地壳构造与地壳应力文集》2010,(0)
软弱场地的地震动效应问题一直是工程地震学的研究重点。本文所说的软弱场地主要对应场地分类中的Ⅳ类场地,覆盖层较厚并含有软弱土夹层,以天津滨海地区为主要代表。研究表明,场地土本身对地震动具有放大作用,而软夹层具有减震作用,含软夹层的软弱场地对地震动参数的影响可以认为是场地土和软夹层对地震动参数的影响共同叠加的结果。叠加的结果将使其具有不同于其他场地的特点。本文选取了天津滨海地区不同地点的钻孔实例来进行计算,说明这类场地对地震动参数的影响。从计算的结果看,对地表峰值加速度而言,含软夹层的软弱场地的放大系数要小于其他类别场地的放大系数,而且在输入地震动较小时相对于地震动输入是放大作用;在输入地震动峰值较大时,表现为减震作用。对反应谱的特征周期而言,场地越软,反应谱越宽,特征周期值越大,而且随着输入峰值加速度的增加,特征周期也增加。对反应谱平台值来说,场地的影响并不显著。 相似文献
4.
针对基岩明显起伏、土层非均匀分布的典型河口盆地场地,考虑土体非线性特征,采用黏弹性人工边界模拟无限域对地震波动的影响,建立大尺度精细化二维有限元模型,分析了盆地地表地震动幅值、频谱、持时、传递函数特征,探讨了基岩起伏土层的地震动聚集效应及盆地边缘效应。结果表明:(1)盆地近地表土层表现出不同程度的地震动放大效应,且随土层深度增加呈非单调递减特征,基岩突变处地震动聚集效应明显,盆地两侧产生较为显著的边缘效应;场地中、长周期地震动的放大作用显著;(2)多遇地震、偶遇地震和罕遇地震水平时,场地卓越周期依次介于0.35~0.65 s、0.40~0.75 s和0.50~1.05 s之间;给出了盆地地表PGA(地表峰值加速度)、卓越周期均值等值线图及地表加速度反应谱放大因子建议值,地表设计地震动参数amax(地震影响系数)与Tg(特征周期)明显大于现行《建筑抗震设计规范》取值;(3)盆地特殊位置地表地震动持时得到不同幅度增长,且与输入地震动特性相关;(4)该盆地对0.5~2.0 Hz频段基岩地震动的放大效应比较显著,对小于0.2 Hz或大于2.5 Hz的基岩地震动,该盆地地震动放大效应不明显;(5)福州城区及其邻近区域地震动放大效应普遍较大。大尺度二维非线性分析一定程度上能合理反映微地形起伏、土层分布及土体非线性对地震波传播过程的影响。 相似文献
5.
垃圾填埋场稳定影响因素敏感性神经网络分析 总被引:2,自引:0,他引:2
垃圾填埋场稳定影响因素的选取和研究是稳定分析的重要组成部分,而确定主次要因素的方法就是进行影响因素敏感性分析。利用BP神经网络结合正交试验设计方法,对填埋场沿衬里滑移破坏的影响因素进行敏感性分析。通过对工程实例的计算,该方法与传统法有着相同的因素敏感性排序,但决定排序的极差值有所不同。由于该法能考虑多因素同时变化,故其极差值的大小更能反映因素敏感程度的差异。BP神经网络结合正交试验设计法与传统法相比能节省计算工作量。研究结果显示,影响填埋场滑移稳定性的最主要参数为复合衬垫层间最小摩擦角和垃圾的堆填坡角。因素敏感性排序的确定为填埋场的优化设计、施工、试验、运营管理提供了理论依据。 相似文献
6.
合理描述土体动力本构关系对场地设计地震动参数取值的准确性有显著影响。以苏州城区200 m深的钻孔剖面为研究对象,对比分析了一维等效线性波传分析法(ELA法)和基于修正Matasovic本构模型的多自由度集中质量非线性分析法(NLA法)给出的深厚场地地震反应,研究了基岩输入地震动特性和地震基岩面的选取对深厚场地地震反应的影响。结果表明:(1)随基岩地震动强度(PGA)的增大,ELA法给出的地表PGA呈单调递增的特征,而NLA法给出的地表PGA呈先快速增大后缓慢减小或几乎不变的趋势;(2)ELA法和NLA法给出的地表加速度反应谱(Sa谱)在短周期范围内存在明显差异,ELA法对基岩高频地震动具有显著的滤波效应,而NLA法对基岩高频地震动的影响表现为随基岩PGA的增大先放大后减小的特征;(3)随地震基岩面深度的增大,地表Sa谱的谱值呈现出稍许增大的趋势,但对周期T<0.1 s部分,NLA法给出的地表Sa谱的谱值则呈现出稍许减小的现象;(4)中、大震作用下,地表地震动持时不仅与基岩地震动特性有关,还与地震反应分析方法和地震基岩面的选取密切相关,NLA法能更合理地反映基岩地震动强度和上覆土层厚度对地表地震动持时的影响。 相似文献
7.
从地震影响系数曲线的特征周期 出发,提出了分别取 和 作为时域计算瑞利(Rayleigh)阻尼的两个目标频率。通过3种不同厚度的单一土层和1种多层土层模型在3条不同地震动作用下的计算,比较了基于Annie方法和本文方法确定Rayleigh阻尼的时域解,以及基于等效线性化的频域解,结果表明:两种Rayleigh阻尼形式的地表加速度峰值误差都在10%以内,地表加速度反应谱基本一致,但本文方法对土层厚度和输入的地震动不太敏感,即误差随着土层厚度及输入地震动的不同离散性很小,且应用更为简便,无需求土层的自振频率,只需要根据场地类别获得场地特征周期,就可确定Rayleigh阻尼值。 相似文献
8.
土-地下结构体系地震反应的简化分析方法 总被引:1,自引:0,他引:1
基于Penzien提出的土-结构动力相互作用分析的集中质量模型,考虑等价土体的层间剪切刚度与阻尼效应,提出了土-地下结构动力相互作用体系地震反应分析的简化分析方法,选取具有不同地震动特性的Taft波、汶川地震什邡八角波和松潘波作为基岩水平向输入地震动,采用该简化方法和二维有限元法对土-地铁地下车站结构体系的地震加速度反应特性进行了对比分析,结果表明:简化方法计算的地铁地下车站结构峰值加速度反应大于二维有限元法计算的地铁地下车站结构峰值加速度反应,两者的差异与输入地震动特性有关,但其随地铁地下车站结构高度变化的总体趋势较为一致;随着输入地震动强度的增大,其差异程度也有所加大。该简化方法可合理反映土-地下结构体系的动力相互作用效应,可作为地下结构抗震设计分析的一种辅助方法。 相似文献
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10.
《岩土力学》2020,(4)
研究河谷场地地震效应对场地选址和抗震设计具有重要的指导意义。基于离心机振动台试验分析,研究了梯形河谷场地地震动响应规律。结果表明:基岩河谷场地对地震动有一定的放大效应,放大效应随着地形的变化而变化,但放大效应不显著,场地不同位置对反应谱的影响较小;基岩-土模型基岩面地震动放大倍数明显增大,不同输入地震动情况下放大倍数不同,各个场点对频段为0.5~2.5 s的地震动有明显的放大作用,对地震动放大频域范围明显加大,这与纯基岩场地的有明显的不同,虽然各个场点的反应谱形状有一定的差别,但是反应谱的平台值和特征周期相差不大;由于河谷场地地形效应,河谷场地地表峰值加速度随着地形的变化放大倍数随之变化,阶地级数越高放大倍数越大,谷底放大倍数最小,随着输入地震动强度的增加,阶地级数越高反应谱的平台值越高,特征周期越大。 相似文献
11.
Responses of municipal solid waste (MSW) landfills during earthquakes are gaining worldwide importance due to the devastating nature of earthquake on landfills. Apart from the post-earthquake safety and serviceability issues which pose environmental and public health problems, other important concerns are related to the behavior of closed landfills during and after earthquake. In present study, one dimensional (1-D) equivalent-linear analysis was carried out to model the behaviour of MSW landfills subjected to seismic base accelerations using the DEEPSOIL software. Influence of foundation types, height and stiffness of MSW landfills and seismic base accelerations on the seismic responses in terms of surface accelerations, normalized stresses (i.e., shear stress/effective vertical stress) and spectral amplification are evaluated. The results showed that height and stiffness of landfills, type of foundation and amount of seismic base acceleration and period play important role in evaluating the seismic responses of MSW landfills. Assumption of constant unit weight and shear wave velocity for landfills underestimates maximum horizontal acceleration (MHA), normalized shear stresses and spectral amplification at the top of landfills. Landfill models with smaller heights (up to 40 m high) showed higher amplification ratio for low seismic base accelerations with mean period near to that of soil and landfill resonance for all sites. A complex behavior was observed at higher seismic base accelerations due to non-linear behavior of landfill materials. 相似文献
12.
施工弃土堆填保坎对山区输电线路桩基地震反应会产生何种影响,目前尚不明确。采用FLAC3D数值分析软件建立西南山区典型输电线塔位数值模型,分析桩周有无弃土堆填保坎时桩基础地震动力响应的变化情况,开展定量分析,初步探讨弃土堆填保坎对山区输电线路桩基地震反应的影响。研究表明:桩周弃土堆填保坎后斜坡场地桩基桩身水平峰值加速度、桩身位移、桩身内力、桩周土体位移差的量值均较桩周无弃土堆填保坎时增大。陡坡坡度为35°时,弃土堆填保坎增大了桩基础地震响应,降低了其在陡坡上的抗震性能。 相似文献
13.
Estimation of seismic yield acceleration for the municipal solid waste landfills is the basic step for design to mitigate
the hazard of earthquake on landfills. For most of the landfills constructed in the seismic zones, influence of the vertical
component of seismic acceleration is often neglected assuming that it is not in phase with the horizontal seismic acceleration
and hence does not affect the design parameters largely. Conventional pseudo-static analysis using limit equilibrium method
does not consider the variation of seismic inertial forces with time and also effect of vertically propagating shear and primary
waves, which can have serious effect on the design values. To overcome the limitations of existing methodology, in the present
study, pseudo-dynamic approach, which takes into account the effects of time, primary and secondary waves, frequency of excitation,
is applied for the first time for dynamic analysis of landfills for three different typical practical geometries of landfills.
Chosen sets of landfills resemble some of the existing landfill geometries. Design equations and charts are developed for
factor of safety against base sliding and seismic yield acceleration for these three typical landfill geometries. The results
are compared with the similar results obtained by using conventional pseudo-static analysis, and the influence of vertical
seismic acceleration on factor of safety against base sliding and yield acceleration is reported. 相似文献
14.
不同降雨模式下山谷型垃圾填埋场水分运移及其稳定性研究 总被引:2,自引:0,他引:2
近10年的运营经验表明,国内南方地区第1批建造的山谷型垃圾填埋场中的渗滤液水位一般较高。同时,现有研究表明,降雨入渗引起渗滤液水位过高是垃圾填埋场失稳的主要诱因之一。因此,研究强降雨条件下山谷型垃圾填埋场的水分运移规律及其稳定性,具有重要的现实意义。基于七子山填埋场浅层、中层和深层垃圾土的土-水特征曲线和Brooks-Corey公式,利用非线性拟合技术得到垃圾土的渗透性函数;运用饱和-非饱和渗流理论,对递减型、中心型、增强型和平均型4种降雨模式下七子山填埋场的水分运移进行了数值计算;利用极限平衡理论,对不同降雨模式下七子山填埋场的稳定性进行了分析。结果表明,降雨模式对山谷型垃圾填埋场内的水分运移规律和填埋场的稳定性有显著的影响,递减型降雨模式下填埋场内孔隙水压的变化最大,同时填埋场稳定系数也下降最为明显,为最不利降雨模式;经历7 d 746 mm的极端强降雨后,七子山填埋场具有极大的失稳隐患。 相似文献
15.
Bioreactor landfills are operated to enhance refuse decomposition, gas production, and waste stabilization. The major aspect
of bioreactor landfill operation is the recirculation of collected leachate back through the refuse mass. Due to the presence
of additional leachate and accelerated decomposition, the characteristics of Municipal Solid Waste (MSW) in bioreactor landfills
are expected to change. About 50% of the continental United States comes under the designated seismic impact zone. The federal
regulations have focused increase attention on seismic design of solid waste fills, and have mandated that the solid waste
landfills located in the seismic impact zones should be designed to resist the earthquake. Accordingly, assessment of dynamic
properties of landfills is one of the major geotechnical tasks in landfill engineering. In order to understand the changes
in dynamic properties of bioreactor waste mass with time and decomposition, four small scale bioreactor landfills were simulated
in laboratory and samples were prepared to represent each phase of decomposition. The state of decomposition was quantified
by methane yield, pH, and volatile organic content (VOC). A number of Resonant Column (RC) tests were performed to evaluate
the dynamic properties (stiffness and damping) of MSW. The test results indicated that the normalized shear modulus reduction
and damping curves are significantly affected by the degree of decomposition. The shear modulus increased from 2.11 MPa in
Phase I to 12.56 MPa in Phase IV. The increase was attributed to the breakdown of fibrous nature of solid waste particles
as it degrades. Therefore, considering MSW properties to be uniform throughout the bioreactor landfill is not a reasonable
assumption and the shear modulus reduction curves should be evaluated based on the degree of MSW decomposition, rather than
the sample composition itself. 相似文献
16.
Rajiv K. Giri 《Geomechanics and Geoengineering》2015,10(2):126-138
In bioreactor landfills, different configurations of closely spaced horizontal trench (HT) systems are often considered as leachate recirculation systems to achieve uniform and rapid distribution of moisture in municipal solid waste (MSW). In this study, a numerical two-phase flow modelling was adopted to study the effects of geometric configuration of HT systems on the moisture distribution in MSW, and the stability of a simplified bioreactor landfill slope during continuous and intermittent leachate recirculation. Transient variations in pore water and capillary pressures in MSW were assessed, and slope stability analyses were performed using strength reduction technique. MSW was considered as heterogeneous and anisotropic with varied unit weight and saturated hydraulic conductivity. The results demonstrated that geometric configurations of HT systems significantly affected the moisture distribution, generation and distribution of pore water and capillary pressures in MSW, and considerably influenced the mechanical stability of bioreactor landfill slope. It was concluded that staggered configuration of closely spaced HT systems with intermittent sequences of leachate recirculation and subsequent gravity drainage in alternate shallow and deep HT layers should be adopted as they produce uniform moisture distribution and ensure the mechanical stability of landfill slope due to low induced pore pressures near side slope. Overall, this study presents a significant contribution to the understanding of the basic mechanisms controlling the geotechnical stability of bioreactor landfills during leachate operations. Furthermore, the capability of the adopted commercial code was verified with complexities related to bioreactors behaviour. However, further research is needed to validate the model based on field monitoring data at actual bioreactor landfills. 相似文献
17.
A bioreactor landfill is operated to enhance refuse decomposition, gas production, and waste stabilization. Some of the potential
advantages of bioreactor include rapid stabilization of waste, increased landfill gas generation, gain in landfill space,
enhanced leachate treatment, and reduced post closure maintenance period. Due to the accelerated decomposition and settlement
of solid waste, bioreactor landfills are gaining popularity as an alternative to the conventional Subtitle D landfills. However,
the addition of leachate to accelerate the decomposition changes the physical and engineering characteristic of waste and
therefore affects the geotechnical characteristics of waste mass. The changes in the physical and mechanical characteristics
of solid waste with time and decomposition are expected to affect the shear strength of waste mass. The objective of this
paper is to analyze the stability of solid waste slopes within the bioreactor landfills, as a function of time and decomposition.
The finite element program PLAXIS is used for numerical modeling of bioreactor landfills. Stability analysis of bioreactor
landfills was also performed using limit equilibrium program STABL. Finally the results from finite element program PLAXIS
and limit equilibrium program STABL are compared. GSTABL predicted a factor of safety of more than 1 in all the cases analyzed,
whereas PLAXIS predicted a factor of safety of less than 1 at advanced stages for a slope of 2:1. However, the interface failures
between solid waste and landfill liners have not been considered in this paper. 相似文献
18.
将加、卸载响应比理论引入地下岩体洞室群地震响应分析中。以输入的地震加速度作为加、卸载,以洞室围岩的加速度作为响应,合理地确定了加、卸载响应区段。通过有限差分程序FLAC3D建立了白鹤滩水电站13号机组剖面数值分析模型,选用汶川地震波进行动力时程计算,探讨地下岩体洞室群的地震动力稳定性,研究结果表明:在100年超越概率2%的地震作用下,白鹤滩水电站地下洞室群围岩响应比峰值范围在4.05~11.52之间;结合应力及位移分析,主厂房拱顶及层间错动带C4在尾调室上游边墙出露部位的围岩均进入了非线性变形状态,但响应比在整个时程中并没有趋于无穷大,围岩没有发生失稳破坏;错动带两侧的围岩产生了一定的相对位移,会对尾调室的边墙稳定性产生不利影响。该研究方法可应用于一般地下岩体结构的地震稳定性分析中。 相似文献
19.
This paper extends a previously developed three-part wedge method for the seismic stability analysis of the landfill with a triangular berm using pseudo-static method, and moreover, the translation failure condition of the landfill along under bottom of the berm is only presented. In the seismic impact zone, it is necessary to consider the impact of the seismic force on the stability of the landfill. Generally, apart from the horizontal seismic force, the landfill is also subjected to both upward and downward vertical seismic forces. The downward vertical seismic force has a positive impact on the seismic stability of the landfill, while the upward vertical seismic force is just opposite. Therefore, simply ignoring vertical seismic force, the seismic stability of the landfill will be overestimated or underestimated in the seismic condition. Besides, the seismic yield coefficient is calculated by assuming FSV = 2FS and the ratio of vertical seismic coefficient to horizontal seismic coefficient is equal to 2/3. 相似文献