共查询到19条相似文献,搜索用时 203 毫秒
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夯击能应用于高填土地基的一些探讨 总被引:2,自引:0,他引:2
大量工程实践表明 ,对填土及软土地基进行夯击加固时 ,夯击能的选取不仅与填土层的厚度有关 ,而且与填土层下覆土质的工程地质条件等因素密切相关。本文结合南方某港口填土地基加固工程实例 ,对在高填土地层中夯击能的使用问题进行了探讨 ,分析了当填土层的下卧层分别为坚硬土层和软弱土层、以及当填土层的填料分别为粗颗粒料和含水量较高的粘性土等细粒填料时 ,填土层加固的机理 ,制定了在不同条件下选取夯击能的标准 ,并根据现场检测资料 ,评价了该场地的地基加固效果 ,进一步验证了所确定夯击能标准的可靠性。 相似文献
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强夯动力性能的显式非线性数值分析 总被引:3,自引:2,他引:1
充分考虑碰撞中出现的材料非线性、几何非线性、接触非线性、运动非线性以及它们之间相互耦合的特性,利用显式瞬态非线性有限元分析技术分析了强夯对地基土的冲击碰撞过程,得到了夯锤与土体之间的撞击力时间历程、土体位移、应力的时间历程,并得到了落距、夯锤重量、夯锤底面积与强夯加固深度之间的相互关系,分析结果表明:土体位移滞后于土体应力,再现了夯锤与土体碰撞的整个过程,反映了强夯过程中的一般现象和基本规律。 相似文献
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静动力排水固结法处理淤泥软基振动试验研究 总被引:3,自引:0,他引:3
对于高含水率、大孔隙比的深厚淤泥地基,在静动力排水固结法处理中,采用组合式高效夯击减震锤(SAAT)等4种不同形状尺寸的典型夯锤,以975~1 125 kN•m单击夯击能夯击,进行场地振动加速度及夯沉量原位对比测试,获得SAAT夯锤与地基土首次接触、回弹和二次作用历时分别为15,80,35 ms,各锤作用下竖向与水平向加速度分别在10 m与5 m距离内急剧降低,得到满足规范(烈度Ⅶ度)安全要求时SAAT及各夯锤夯击综合安全距离为20~30 m,其中SAAT所需安全距离最小。结果表明,采用SAAT可明显提高夯击效率,并可有效地减小对周边环境的振动影响。此外,对该条件下夯击冲击波的传播及衰减规律进行了总结与分析。 相似文献
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低能量强夯法加固粉质黏土地基试验研究 总被引:5,自引:1,他引:4
结合上海某铁路集装箱中心站地基处理工程,针对其场区上部粉质黏土、下部砂质粉土的地基条件,对低能量强夯法加固此类地基的适用性进行了现场试验研究。通过对夯击过程中超静孔隙水压力随夯击次数、深度、距离的变化规律及在不同性质土层中的增长与消散规律的研究,提出了运用试验手段确定强夯夯击次数、夯点间距、有效加固深度及两遍强夯间隔时间等施工参数的方法。同时,用静力触探试验和标准贯入试验对地基加固的效果进行了检验,结果说明低能量强夯法加固粉质黏土地基的适用性,从而进一步拓宽了低能量强夯法的应用范围。 相似文献
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为了掌握高能级强夯作用下土体的变形特性,在LS-DYNA的框架内,采用非线性大变形显示有限元算法和“帽子”本构模型,计算了强夯作用下地基土体的变形。首先,根据现场施工的实际情况建立了有限元基本模型,并与实际的监测数据进行比较,其计算结果与测试结果基本一致,该模型能较好地反映出土体的隆起和侧向位移特点。其次,以该基本模型和夯坑的变形为考察对象进行参数分析,研究了不同能级、同能级不同动量以及夯锤与地基土间的水平摩擦力对土体变形的影响。结果表明,高能级强夯作用下夯锤与地基土间的水平力是不可忽略;夯锤与地基土之间的摩擦力,对夯坑侧向的土体位移和地表的隆起有明显的影响 相似文献
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夯击方式对强夯加固效果的影响 总被引:4,自引:1,他引:3
工程实践表明,“重锤低落距”和“轻锤高落距”的作用效果有较大差别。在考虑材料非线性、几何非线性、接触非线性、运动非线性以及它们之间相互耦合特性的基础上,利用显式瞬态非线性有限元分析技术分析了强夯夯锤对地基土的冲击碰撞过程,得到了土体的运动轨迹、夯锤与土体之间的最大撞击力、撞击持续时间、夯沉等结果,分析了不同夯击方式下的能量利用效率及土的物理力学指标对夯击方式的敏感性,结果表明“重锤低落距“优于”轻锤高落距”这一结论是有条件的。 相似文献
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根据强夯的特点,采用同时考虑几何非线性、材料非线性、状态非线性,并且考虑瞬态大变形的非线性动态显式有限元,分析了强夯对地基土的冲击碰撞过程。该方法克服了以往有限元计算强夯动力问题时需再引入其他的简化假定的已知量,能较实际地反映强夯加固的动力特性。通过对工程实例计算研究,取得了令人满意的效果。 相似文献
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This paper outlines the development as well as implementation of a numerical procedure for coupled finite element analysis of dynamic problems in geomechanics, particularly those involving large deformations and soil-structure interaction. The procedure is based on Biot’s theory for the dynamic behaviour of saturated porous media. The nonlinear behaviour of the solid phase of the soil is represented by either the Mohr Coulomb or Modified Cam Clay material model. The interface between soil and structure is modelled by the so-called node-to-segment contact method. The contact algorithm uses a penalty approach to enforce constraints and to prevent rigid body interpenetration. Moreover, the contact algorithm utilises a smooth discretisation of the contact surfaces to decrease numerical oscillations. An Arbitrary Lagrangian–Eulerian (ALE) scheme preserves the quality and topology of the finite element mesh throughout the numerical simulation. The generalised-α method is used to integrate the governing equations of motion in the time domain. Some aspects of the numerical procedure are validated by solving two benchmark problems. Subsequently, dynamic soil behaviour including the development of excess pore-water pressure due to the fast installation of a single pile and the penetration of a free falling torpedo anchor are studied. The numerical results indicate the robustness and applicability of the proposed method. Typical distributions of the predicted excess pore-water pressures generated due to the dynamic penetration of an object into a saturated soil are presented, revealing higher magnitudes of pore pressure at the face of the penetrometer and lower values along the shaft. A smooth discretisation of the contact interface between soil and structure is found to be a crucial factor to avoid severe oscillations in the predicted dynamic response of the soil. 相似文献
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This paper presents a ‘Eulerian‐like’ finite element technique to simulate the large accumulated displacements of piles subjected to multiple hammer blows. For each hammer blow, results are obtained using a standard small strain finite element model and, at the end of each hammer blow, material flow is taken into account with reference to a fixed finite element mesh. Residual stresses calculated at the Gauss integration points of the deformed finite element mesh are mapped on to the fixed finite element mesh, and these stresses are used as initial stresses for the next hammer blow. At the end of each hammer blow, stiffness and mass matrices are recalculated for the volume of material remaining inside the fixed finite element mesh. Results obtained with and without allowing material to flow through the fixed mesh are compared for several hammer blows. Build up of residual stresses, soil flow and yielded points around the pile are presented for plugged, partially‐plugged and unplugged piles. Using the new finite element technique, the driving of a pile from the soil surface is studied. The ability to analyse this and other large deformation problems is the main advantage of the new finite element technique. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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强夯法处理层状软基的动态响应分析 总被引:2,自引:1,他引:1
引入双屈服面弹塑性本构模型,将土骨架的变位和孔隙水作为变量进行流、固耦合分析,通过瞬态波动有限元程序模拟冲击荷载作用下层状地基土体的动态响应特征。计算结果表明,土体的应力峰值、孔压峰值和位移峰值随土层深度和距锤底中心的径向距离的增大而逐渐滞后,通过不同位置土体的动态响应分析,表明应力波是以竖向的椭球面形状在土体中传播的,而且衰减很快。数值计算结果与现场测试结果两者之间较为吻合,为实现有限元模拟分析现场实际提供了可靠的依据。 相似文献
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冻土路基在地震作用下的动力响应 总被引:1,自引:1,他引:0
青藏高原是地震多发区,冻土区的公路、铁路在地震作用下的动力响应必须考虑.将冻土作为黏弹塑性材料,考虑冻土在动力荷载作用下的热力耦合效应,从热传导方程、渗流微分方程和动力平衡方程出发,建立了冻土的动力热一力耦合微分方程.根据相应的有限元列式,对路基在地震荷载作用下的动力响应进行了计算与分析. 相似文献
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A comprehensive analytical solution is developed in this paper to investigate the torsional vibration of an end bearing pile embedded in a homogeneous poroelastic medium and subjected to a time-harmonic torsional loading. The poroelastic medium is modeled using Biot’s two-phased linear theory and the pile using one-dimensional elastic theory. By using the separation of variables technique, the torsional response of the soil layer is solved first. Then based on perfect contact between the pile and soil, the dynamic response of the pile is obtained in a closed form. Numerical results for torsional impedance of the soil layer are presented first to portray the influence of wave modes, slenderness ratio, pile–soil modulus ratio and poroelastic properties. A comparison with the plane strain theory is performed. The selected numerical results are obtained to analyze the influence of the major parameters on the torsional impedance at the level of the pile head. Finally, the dynamic torsional impedance of this study is compared with that for floating pile in elastic soil. 相似文献
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针对重力式挡土墙墙后分层填土对墙身受力影响的问题,深入研究分析墙背土压力动态变化值及规律性,利用大型通用有限元分析软件ADINA,建立了平面应变单元及墙、土接触单元的有限元计算模型,并且综合考虑墙后回填土Mo-hr-Coulomb材料本构模型,初始地应力场平衡、墙后回填土分层碾压填筑,设置墙、土之间的接触受力进行有限元... 相似文献
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为了分析阶梯钻头冲击挤密作用下土体的变形机理,将土体视为DP材料,服从Drucker-Prager屈服准则,通过钻具与土体之间的接触以及施加冲击载荷来模拟钻进过程,建立了潜孔锤冲击挤密钻进的有限元模型。以非线性瞬态动力学有限元分析为手段,利用有限元软件ANSYS9.0对阶梯钻头冲击挤密作用下土体的变形机理进行了模拟分析。结果表明,在冲击载荷作用下,冲击功主要用于竖向压缩土体,水平方向的挤压作用相对较小。阶梯钻头对土体的破坏作用可以看作是每个台阶的微剪切作用,当台阶布置合理时,土体沿等效锥面整体破坏,破坏后的土体在等效锥面的作用下被挤向孔壁四周,挤密效果较好。 相似文献