斜入射地震波引起的动应力路径理论与数值研究
发布时间：2018-09-10 13:58
【摘要】：地震作用在土中产生的动应力路径对研究岩土体在地震灾变中的力学特性演化至关重要。土动力学中常沿用Seed的简化方法将地震视为垂直入射的剪切波,采用刚性地基模型估算地震动应力。近年来强震频发,具有显著斜入射特点的地震波产生的动应力路径特征尚不明确,并且地震波中P波作用不可小觑。本论文基于波动理论,通过数学推导、参数分析以及数值模拟等方法分析探讨了斜入射P波、SV波产生的动应力路径的形式及其影响因素敏感性,主要工作及结论如下:1、本文推导了半无限弹性空间中任一深度处由单一 P波、SV波斜入射产生的动应力及动应力路径解析式,从数学上证明在剪应力分量(偏差正应力-水平剪应力)组成的平面中,斜入射地震波产生的动应力路径形状为斜椭圆形。在地震波参数和地基材料参数的组合下,斜椭圆形式多变,形成如圆形、直线形等,可视为斜椭圆的特例。2、系统地分析了斜椭圆应力路径的影响因素和可能变化范围,表明入射角、泊松比和单位波长深度是影响应力路径的根本因素。斜入射工况下,动应力水平有可能更高,其中P波斜入射角度在30°～60°范围内时引起的动偏应力幅峰值最大,SV波斜入射角为20～40°之间在近饱和的地基产生的动应力最大。3、基于FLAC有限差分软件阻尼(静态)人工边界,实现了斜入射地震波的动力输入,模拟了成层地基与含地下洞室地基中地震波斜入射P波、SV波产生的动应力响应,分析了不同条件下形成的路径形式差异,并探讨了复杂场地条件对动应力响应的影响规律。结果表明,含软夹层层状地基中软夹层的斜椭圆应力路径相比一般上软下硬地基差异明显,形状趋于接近圆的水平椭圆,软夹层是最容易发生液化的位置。含地下洞室场地的动应力响应与无洞室地基存在巨大差异,但洞室上方的土体差异最小,这一差异的影响范围大于一倍洞室直径的距离,并且随着地基刚度的增大,这一范围也将扩大。
[Abstract]:The dynamic stress path generated by earthquake action in soil is very important to study the evolution of mechanical properties of rock and soil in earthquake disaster. In soil dynamics, the simplified method of Seed is often used to treat earthquakes as shear waves of vertical incidence, and the rigid foundation model is used to estimate the ground motion stress. In recent years, the characteristics of dynamic stress path produced by seismic waves with significant oblique incidence and frequent strong earthquakes are still unclear, and the effect of P wave in seismic waves is not negligible. Based on the wave theory, the form of dynamic stress path and the sensitivity of the influencing factors of the oblique incident P-wave SV wave are discussed by mathematical derivation, parameter analysis and numerical simulation. The main work and conclusions are as follows: 1. In this paper, the analytical expressions of dynamic stress and dynamic stress path generated by the oblique incidence of a single P-wave SV wave at any depth in a semi-infinite elastic space are derived. It is mathematically proved that in the plane composed of shear stress component (deviation normal stress and horizontal shear stress), the dynamic stress path generated by oblique incident seismic waves is obliquely elliptical. Under the combination of seismic wave parameter and foundation material parameter, the oblique ellipse type is changeable, forming such as circle, straight shape and so on, which can be regarded as the special case of oblique ellipse. The influence factors and possible variation range of oblique ellipse stress path are analyzed systematically. It is shown that the incident angle, Poisson's ratio and depth per unit wavelength are the fundamental factors affecting the stress path. At oblique incidence conditions, the dynamic stress level is likely to be higher, When the incidence angle of P-wave oblique is in the range of 30 掳to 60 掳, the maximum amplitude of dynamic deflection stress caused by the peak amplitude of SV wave and the maximum incidence angle of SV wave are between 20 掳and 40 掳. The maximum dynamic stress in the near saturated foundation is obtained. Based on the damping (static) artificial boundary of FLAC finite difference software, The dynamic input of oblique incident seismic wave is realized, and the dynamic stress response caused by oblique incident P wave SV wave in layered foundation and underground cavern foundation is simulated, and the difference of path forms under different conditions is analyzed. The effect of complex site conditions on dynamic stress response is also discussed. The results show that the stress paths of oblique ellipse in layered foundation with soft intercalation are obviously different from those of upper soft and hard foundation, and the shape of the horizontal ellipse tends to be close to the circle, and the soft interlayer is the position where liquefaction is most likely to occur. There is a great difference between the dynamic stress response of the underground cavern site and the ground without cavern, but the difference of soil mass above the cavern is the smallest, the influence range of this difference is larger than the distance of the diameter of the cavern, and with the increase of the foundation stiffness, This scope will also be expanded.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU435
本文编号：2234643
[Abstract]:The dynamic stress path generated by earthquake action in soil is very important to study the evolution of mechanical properties of rock and soil in earthquake disaster. In soil dynamics, the simplified method of Seed is often used to treat earthquakes as shear waves of vertical incidence, and the rigid foundation model is used to estimate the ground motion stress. In recent years, the characteristics of dynamic stress path produced by seismic waves with significant oblique incidence and frequent strong earthquakes are still unclear, and the effect of P wave in seismic waves is not negligible. Based on the wave theory, the form of dynamic stress path and the sensitivity of the influencing factors of the oblique incident P-wave SV wave are discussed by mathematical derivation, parameter analysis and numerical simulation. The main work and conclusions are as follows: 1. In this paper, the analytical expressions of dynamic stress and dynamic stress path generated by the oblique incidence of a single P-wave SV wave at any depth in a semi-infinite elastic space are derived. It is mathematically proved that in the plane composed of shear stress component (deviation normal stress and horizontal shear stress), the dynamic stress path generated by oblique incident seismic waves is obliquely elliptical. Under the combination of seismic wave parameter and foundation material parameter, the oblique ellipse type is changeable, forming such as circle, straight shape and so on, which can be regarded as the special case of oblique ellipse. The influence factors and possible variation range of oblique ellipse stress path are analyzed systematically. It is shown that the incident angle, Poisson's ratio and depth per unit wavelength are the fundamental factors affecting the stress path. At oblique incidence conditions, the dynamic stress level is likely to be higher, When the incidence angle of P-wave oblique is in the range of 30 掳to 60 掳, the maximum amplitude of dynamic deflection stress caused by the peak amplitude of SV wave and the maximum incidence angle of SV wave are between 20 掳and 40 掳. The maximum dynamic stress in the near saturated foundation is obtained. Based on the damping (static) artificial boundary of FLAC finite difference software, The dynamic input of oblique incident seismic wave is realized, and the dynamic stress response caused by oblique incident P wave SV wave in layered foundation and underground cavern foundation is simulated, and the difference of path forms under different conditions is analyzed. The effect of complex site conditions on dynamic stress response is also discussed. The results show that the stress paths of oblique ellipse in layered foundation with soft intercalation are obviously different from those of upper soft and hard foundation, and the shape of the horizontal ellipse tends to be close to the circle, and the soft interlayer is the position where liquefaction is most likely to occur. There is a great difference between the dynamic stress response of the underground cavern site and the ground without cavern, but the difference of soil mass above the cavern is the smallest, the influence range of this difference is larger than the distance of the diameter of the cavern, and with the increase of the foundation stiffness, This scope will also be expanded.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU435
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