【摘要】：地震作用在土中產(chǎn)生的動應(yīng)力路徑對研究巖土體在地震災(zāi)變中的力學(xué)特性演化至關(guān)重要。土動力學(xué)中常沿用Seed的簡化方法將地震視為垂直入射的剪切波,采用剛性地基模型估算地震動應(yīng)力。近年來強(qiáng)震頻發(fā),具有顯著斜入射特點(diǎn)的地震波產(chǎn)生的動應(yīng)力路徑特征尚不明確,并且地震波中P波作用不可小覷。本論文基于波動理論,通過數(shù)學(xué)推導(dǎo)、參數(shù)分析以及數(shù)值模擬等方法分析探討了斜入射P波、SV波產(chǎn)生的動應(yīng)力路徑的形式及其影響因素敏感性,主要工作及結(jié)論如下:1、本文推導(dǎo)了半無限彈性空間中任一深度處由單一 P波、SV波斜入射產(chǎn)生的動應(yīng)力及動應(yīng)力路徑解析式,從數(shù)學(xué)上證明在剪應(yīng)力分量(偏差正應(yīng)力-水平剪應(yīng)力)組成的平面中,斜入射地震波產(chǎn)生的動應(yīng)力路徑形狀為斜橢圓形。在地震波參數(shù)和地基材料參數(shù)的組合下,斜橢圓形式多變,形成如圓形、直線形等,可視為斜橢圓的特例。2、系統(tǒng)地分析了斜橢圓應(yīng)力路徑的影響因素和可能變化范圍,表明入射角、泊松比和單位波長深度是影響應(yīng)力路徑的根本因素。斜入射工況下,動應(yīng)力水平有可能更高,其中P波斜入射角度在30°～60°范圍內(nèi)時引起的動偏應(yīng)力幅峰值最大,SV波斜入射角為20～40°之間在近飽和的地基產(chǎn)生的動應(yīng)力最大。3、基于FLAC有限差分軟件阻尼(靜態(tài))人工邊界,實(shí)現(xiàn)了斜入射地震波的動力輸入,模擬了成層地基與含地下洞室地基中地震波斜入射P波、SV波產(chǎn)生的動應(yīng)力響應(yīng),分析了不同條件下形成的路徑形式差異,并探討了復(fù)雜場地條件對動應(yīng)力響應(yīng)的影響規(guī)律。結(jié)果表明,含軟夾層層狀地基中軟夾層的斜橢圓應(yīng)力路徑相比一般上軟下硬地基差異明顯,形狀趨于接近圓的水平橢圓,軟夾層是最容易發(fā)生液化的位置。含地下洞室場地的動應(yīng)力響應(yīng)與無洞室地基存在巨大差異,但洞室上方的土體差異最小,這一差異的影響范圍大于一倍洞室直徑的距離,并且隨著地基剛度的增大,這一范圍也將擴(kuò)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 擄to 60 擄, 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 擄and 40 擄. 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.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU435

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