钻孔应变差应变耦合系数反演与有关机理的探讨

研究反演分量式钻孔应变差应变耦合系数的方法,采用考虑方位角校正和相位滞后影响两种计算模型,计算结果显示大多数测站采用两种方法反演的耦合系数均比较相近,相位滞后、方位角校正以及拟合残差的结果相对稳定;但是有部分测站的差应变相位滞后偏离较大,从而导致采用两种方法反演的耦合系数差异较大。结合测站周边的构造分布,对可能导致该现象的物理机制进行了探讨。     

Analytic properties of Hansen coefficients

Hansen’s coefficients in the theory of elliptic motion with eccentricity e are studied as functions of the parameter η = (1 − e ²)^1/2. Their analytic behavior in the complex η plane is described and some symmetry relations are derived. In particular, for every Hansen coefficient, multiplication by suitable powers of e and η results in an entire analytic function of η. Consequently, Hansen’s coefficients can be in principle computed by means of rapidly convergent series in powers of η. A representation of Hansen’s coefficients in terms of two entire functions of e ² follows.      

Pseudo-static bearing capacity of shallow foundations on heterogeneous marine deposits using limit equilibrium method

Abstract

By application of the limit equilibrium method associated with Coulomb failure mechanism, the effect of variation of undrained shear strength with depth on seismic bearing capacity was evaluated. The approach followed in this study to take into account seismic forces is pseudo-static. It is also assumed that the occurrence of an earthquake does not have any effects on the values of soil cohesion. Two different marine soil deposits exhibiting linear and bilinear variations of undrained shear strength with depth were considered. The undrained bearing capacity factor has been computed as a function of dimensionless parameters of λ₁B/c₀, λ₂B/c₀, and Z_t/B. The results of this paper have been compared with solutions reported in the literature, and the consistency of the results confirmed the ability of Coulomb failure mechanism and its corresponding limit equilibrium method formulation in static condition. Furthermore, the pseudo-static bearing capacity of shallow foundations on heterogeneous marine deposit is addressed. Finally the results of this study presented in the form of table and design charts.     

乳山震群震源谱参数的稳健反演

本文引入截止频率f_(max)提出基于Brune模型的高频截止(High-Cut)模型,采用两步反演的方法来拟合求解震源谱的特征参数,并给出其误差范围;实际应用显示该模型的理论谱对观测谱有很好的拟合,可明显改善拐角频率识别的准确度.将该方法应用于2013—2015年的乳山震群,计算了乳山震群25次M_L≥3.0事件的震源参数(地震矩、破裂半径、应力降等),进一步对乳山震群的震源破裂特性进行了讨论.结果显示:拐角频率、应力降与震源尺度大小明显相关;高频衰减系数γ与震源破裂区的复杂程度以及破裂性质有关,当观测记录中混杂有其他事件的波形或微破裂时,高频衰减系数大于2,并且不确定性增大;截止频率f_(max)与地震大小存在一定相关性;使用Beresnev(2001)给出的震源半径计算公式,得到的乳山震群的结果显示与华北地区的经验关系较为一致;乳山震群的应力降明显偏小(最大不超过0.15 MPa),一方面反映了震中区域的构造应力水平,另一方面可能还意味着此次震群是一个相对非耗散型的脆性破裂过程,属于低摩擦应力的断层作用.     

任意排列的空心管桩屏障对SH波的多重散射

提出1种可计算任意排列、任意圆截面尺寸的多排空心管桩对平面SH波多重散射的理论求解方法。考虑第1重散射即为通常所谓的单重散射,对特定管桩第2重散射的入射波为在各管桩所受的第1重散射波之和,亦即第1重散射所激发的次生波源,以此类推至第m重散射。假设每重散射在桩-土边界以及管桩内部均满足弹性边界条件,将入射波、散射波及透射波采用波函数展开,并运用Graf加法定理移轴获得待定的各重散（透）射复系数,得到总散射及管桩内部透射波场的理论解。算例中讨论了散射重数、桩径与桩（排）间距之比、桩-土剪切模量之比、管桩内外径之比以及多排管桩的几何参数等对屏障隔离效果的影响,结果表明,管桩可取得比实心桩更好的屏蔽效果,同时对管桩非连续屏障的工程设计提供了有价值的理论参考依据。     

基于岭参数的谱修正迭代法及其在有理多项式参数求解中的应用

通过比较基于L-曲线法求取岭参数的岭估计法与谱修正迭代法,分析了两种方法的特性,为选择合适的方法进行病态方程求解作参考。针对谱修正迭代法收敛慢、效率低这一缺点,提出了一种利用狭义岭估计中的岭参数(或广义岭估计的岭参数对角矩阵)进行谱修正,改进谱修正迭代法的方法。利用模拟算例对改进的方法进行实验,在不同噪声情况下,改进方法效率有不同程度的提高。把改进方法应用到SPOT影像RPC求解中,发现改进的方法在应用中具有一定的优势。     

Nodal-based three-dimensional discontinuous deformation analysis (3-D DDA)

This paper presents a new numerical model that can add a finite element mesh into each block of the three-dimensional discontinuous deformation analysis (3-D DDA), originally developed by Gen-hua Shi. The main objectives of this research are to enhance DDA block’s deformability. Formulations of stiffness and force matrices in 3-D DDA with conventional Trilinear (8-node) and Serendipity (20-node) hexahedral isoparametric finite elements meshed block system due to elastic stress, initial stress, point load, body force, displacement constraints, inertia force, normal and shear contact forces are derived in detail for program coding. The program code for the Trilinear and Serendipity hexahedron elements have been developed, and it has been applied to some examples to show the advantages achieved when finite element is associated with 3-D DDA to handle problems under large displacements and deformations. Results calculated for the same models by use of the original 3-D DDA are far from the theoretical solutions while the results of new numerical model are quite good in agreement with theoretical solutions; however, for the Trilinear elements, more number of elements are needed.     

用变分方法估算淮河流域总体输送系数

利用2001年6～7月间在安徽肥西的边界层观测资料,利用变分方法计算地面动量通量和感热通量,进而分别估算该处动量总体输送系数和感热总体输送系数。用变分方法计算的地面粗糙度为0.03m。在中性条件下,10m高处平均动量总体输送系数和感热总体输送系数分别为4.83×10-3和3.81×10-3,比值是1.27。总体输送系数具有明显的日变化特征,中午时段最大,夜晚最小;总体输送系数与大气稳定度存在明显关联,文中给出它们之间的拟合关系式;随着高度的增加总体输送系数减少,但减少幅度逐渐变小。     

半潜式超大型浮式结构水动力系数研究

以半潜式超大型浮式结构在动力响应分析中的各水动力系数为研究对象,经理论推导得到D’Alembert动力学方程中的移动式海上基地(MOB)单模块运动的结构质量、结构附加质量、静恢复力系数的简易计算公式。以MOB的"三模块模型"为例,研究其在6级海况浪向角为0°~90°条件下,各模块的附加质量系数及静恢复力系数的历时规律,以实例MOB中的第1个模块为代表展示了计算结果,并统计其最大值与文献资料中的结果进行对比。结果表明:运用本理论公式计算的结果与文献中所得结果相似,可验证本理论公式的正确性、可行性与合理性,为求解半潜式超大型浮式结构模块动力响应位移及转角提供简便的方法。     

应用屏障进行被动隔振的研究综述

人工振动作为一种新形式的环境污染,被列为世界七大环境公害之一。各种形式的人工振动都涉及弹性波的产生和传播,在既有振源与保护区之间设立屏障来切断弹性波的传播路径,衰减振动能量,降低振动幅度,是目前国际上普通采用的隔振措施。屏障按几何构造可分为两类:连续屏障和非连续屏障。对国内外两类屏障的隔振理论和试验研究进行简述,得出的结论为:(1)连续屏障隔振效果好,但对于低频振源,屏障的深度需达到十几米以上(近似于R波的半波长),在软土和高地下水位地区的工程造价非常高,施工难度也非常大;(2)非连续屏障施工方便,不受深度和场地的限制,不需要进行额外的支护和维护,多排非连续屏障具有更广泛的应用前景。今后应注重和加强多排非连续屏障隔振的三维理论分析和吸振新材料的试验研究。