青藏高原凍土工程走廊場地地震動特征與路基動力響應分析
發(fā)布時間：2018-09-04 19:26
【摘要】：青藏高原凍土工程走廊內(nèi)已建與擬建的國家重大基礎(chǔ)工程密集分布。該區(qū)域地理位置重要、多年凍土工程力學性質(zhì)特殊、地震活動頻繁、全球氣溫變暖迅速以及人為擾動不斷加劇,加快了多年凍土退化,使得寬度不足10公里的凍土工程走廊內(nèi)構(gòu)筑物穩(wěn)定性問題與生態(tài)環(huán)境問題愈顯突出。受多因素耦合作用以及各類構(gòu)筑物之間相互影響,工程走廊內(nèi)的生命線工程在地震動力荷載的疊加作用下將面臨巨大的風險與挑戰(zhàn)。因此,開展工程走廊沿線場地地震動特征探究與擬建高速公路路基動力響應分析,對于該區(qū)重大凍土工程的地震安全性評估具有迫切的現(xiàn)實和科學意義。本文旨在解決地震荷載作用下青藏高原凍土工程走廊沿線場地特征與路基動力響應機制問題,運用綜合現(xiàn)場勘探測試資料、室內(nèi)動三軸試驗、數(shù)值模擬計算等方法,研究分析了工程走廊沿線凍土場地土體的波速特征、凍結(jié)青藏粉質(zhì)粘土的動力學特性、場地地震動特征參數(shù)和路基動力響應。主要研究工作和所得結(jié)論歸納如下:(1)根據(jù)工程走廊場地波速鉆孔資料,分析了凍土場地土體的波速變化特征。歸納資料可得出,凍土的波速值大于非凍土,其縱橫波速比值近似為1.5;隨著地溫的降低和土體含冰量的增加,凍土波速隨之增大。(2)通過對重塑凍結(jié)青藏粉質(zhì)粘土在周期循環(huán)荷載作用下的動三軸試驗,較為系統(tǒng)地研究了不同圍壓、不同負溫、不同含水量和不同頻率條件對凍土動力特性的影響。試驗結(jié)果表明:隨著凍土剪應變幅的增大,阻尼比均呈逐漸增大趨勢,動剪模比呈逐漸減小趨勢;阻尼比隨著圍壓的減小、負溫的降低、含水量的減小、頻率的增大而減小;動剪模比隨著圍壓的增大、負溫的升高、含水量的減小、頻率的增大而減小。(3)基于一維土層地震動反應分析理論,根據(jù)青藏高原內(nèi)的地震地質(zhì)條件、地球物理特征以及地震活動性,開展了凍土場地土層地震反應研究,得到了50年超越概率63%,10%和2%的基巖擬合地震動時程、設(shè)計場地地震動參數(shù)及反應譜。(4)采用二維非線性動力有限元分析方法,通過建立整體式和分離式典型高速公路路基橫斷面,對比分析了50年超越概率63%,10%和2%的青藏地震波作用下2種結(jié)構(gòu)路基的加速度放大效應、應力響應特征和位移響應特征。同時,通過改變分離式路基的分幅間距,得到了不同分幅間距條件對分離式路基動力響應特征的影響。
[Abstract]:Intensive distribution of major national infrastructure projects in the frozen soil engineering corridor of the Qinghai-Xizang Plateau. The important geographical location of the region, the special mechanical properties of permafrost engineering, frequent seismic activity, rapid global warming and increasing anthropogenic disturbance have accelerated the permafrost degradation. The structural stability and ecological environment problems in the permafrost engineering corridor with width less than 10 km are more prominent. Due to the coupling of many factors and the interaction between various structures, lifeline engineering in the corridor will face great risks and challenges under the superposition of seismic dynamic loads. Therefore, it is of urgent practical and scientific significance to study the ground motion characteristics along the engineering corridor and to analyze the dynamic response of the proposed highway subgrade for the seismic safety assessment of the major frozen soil projects in this area. The purpose of this paper is to solve the problems of site characteristics and subgrade dynamic response mechanism along the corridor of frozen soil engineering in the Qinghai-Xizang Plateau under seismic loading, using comprehensive field exploration test data, indoor dynamic triaxial test, numerical simulation calculation and so on. The wave velocity characteristics of frozen soil, the dynamic characteristics of frozen Qinghai-Xizang silty clay, the characteristic parameters of ground motion and the dynamic response of roadbed are studied and analyzed. The main research work and conclusions are summarized as follows: (1) according to the data of wave velocity drilling in engineering corridor, the variation characteristics of wave velocity in frozen soil are analyzed. It can be concluded that the wave velocity of frozen soil is larger than that of non-frozen soil, and the ratio of longitudinal and transverse wave velocities is approximately 1.5. With the decrease of ground temperature and the increase of ice content in soil, The wave velocity of frozen soil increases with it. (2) through the dynamic triaxial test of remolded frozen Qinghai-Tibet silty clay under cyclic load, the different confining pressures and negative temperatures are systematically studied. The influence of different water content and different frequency on the dynamic characteristics of frozen soil. The results show that the damping ratio increases gradually and the dynamic shear die ratio decreases with the increase of shear strain amplitude of frozen soil, and the damping ratio decreases with the decrease of confining pressure, the decrease of negative temperature, the decrease of water content and the increase of frequency. The dynamic shear modulus ratio decreases with the increase of confining pressure, negative temperature, water content and frequency. (3) based on the theory of one-dimensional ground motion response, according to the seismic geological conditions in the Qinghai-Xizang Plateau, Based on the geophysical characteristics and seismic activity, the seismic response of permafrost soil layer is studied, and the 50 year surpassing probability of 63% and 2% of the bedrock is obtained to fit the time history of ground motion. Design site ground motion parameters and response spectrum. (4) by using two-dimensional nonlinear dynamic finite element analysis method, the subgrade cross-section of typical freeway subgrade is established. The acceleration amplification effect, stress response characteristics and displacement response characteristics of two kinds of structural subgrade under the action of Qinghai-Tibet seismic wave with 50 years transcendental probability of 6310% and 2% are compared and analyzed. At the same time, by changing the split-width spacing of the separated subgrade, the influence of the conditions of the split-width spacing on the dynamic response characteristics of the separated roadbed is obtained.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U416.1
本文編號：2223119
[Abstract]:Intensive distribution of major national infrastructure projects in the frozen soil engineering corridor of the Qinghai-Xizang Plateau. The important geographical location of the region, the special mechanical properties of permafrost engineering, frequent seismic activity, rapid global warming and increasing anthropogenic disturbance have accelerated the permafrost degradation. The structural stability and ecological environment problems in the permafrost engineering corridor with width less than 10 km are more prominent. Due to the coupling of many factors and the interaction between various structures, lifeline engineering in the corridor will face great risks and challenges under the superposition of seismic dynamic loads. Therefore, it is of urgent practical and scientific significance to study the ground motion characteristics along the engineering corridor and to analyze the dynamic response of the proposed highway subgrade for the seismic safety assessment of the major frozen soil projects in this area. The purpose of this paper is to solve the problems of site characteristics and subgrade dynamic response mechanism along the corridor of frozen soil engineering in the Qinghai-Xizang Plateau under seismic loading, using comprehensive field exploration test data, indoor dynamic triaxial test, numerical simulation calculation and so on. The wave velocity characteristics of frozen soil, the dynamic characteristics of frozen Qinghai-Xizang silty clay, the characteristic parameters of ground motion and the dynamic response of roadbed are studied and analyzed. The main research work and conclusions are summarized as follows: (1) according to the data of wave velocity drilling in engineering corridor, the variation characteristics of wave velocity in frozen soil are analyzed. It can be concluded that the wave velocity of frozen soil is larger than that of non-frozen soil, and the ratio of longitudinal and transverse wave velocities is approximately 1.5. With the decrease of ground temperature and the increase of ice content in soil, The wave velocity of frozen soil increases with it. (2) through the dynamic triaxial test of remolded frozen Qinghai-Tibet silty clay under cyclic load, the different confining pressures and negative temperatures are systematically studied. The influence of different water content and different frequency on the dynamic characteristics of frozen soil. The results show that the damping ratio increases gradually and the dynamic shear die ratio decreases with the increase of shear strain amplitude of frozen soil, and the damping ratio decreases with the decrease of confining pressure, the decrease of negative temperature, the decrease of water content and the increase of frequency. The dynamic shear modulus ratio decreases with the increase of confining pressure, negative temperature, water content and frequency. (3) based on the theory of one-dimensional ground motion response, according to the seismic geological conditions in the Qinghai-Xizang Plateau, Based on the geophysical characteristics and seismic activity, the seismic response of permafrost soil layer is studied, and the 50 year surpassing probability of 63% and 2% of the bedrock is obtained to fit the time history of ground motion. Design site ground motion parameters and response spectrum. (4) by using two-dimensional nonlinear dynamic finite element analysis method, the subgrade cross-section of typical freeway subgrade is established. The acceleration amplification effect, stress response characteristics and displacement response characteristics of two kinds of structural subgrade under the action of Qinghai-Tibet seismic wave with 50 years transcendental probability of 6310% and 2% are compared and analyzed. At the same time, by changing the split-width spacing of the separated subgrade, the influence of the conditions of the split-width spacing on the dynamic response characteristics of the separated roadbed is obtained.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U416.1
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