A Study on Limit State Design of Ground Structures by Dilatational Strain Energy

本文的目的是利用地震作用下隧道结构周围土体产生的弹性应变能来研究地震作用下隧道结构周围土体的稳定性，并寻求合理的隧道结构周围土体的抗震指标。本文用弹性应变能的概念讨论了平面应变条件下土体材料的稳定性问题。由土体的粘聚力、内摩擦角和平均应力定义的最大值，剪切带在土体中扩展。第二、三章分别采用弹塑性有限元拟静力分析方法对箱形隧道和盾构隧道周围土体的抗震性能进行了研究。极限地震烈度定义为随着地震烈度的增加，地表与隧道上部剪切带连接的时间。通过有限元计算表明，LSI取决于地基的粘聚力、内摩擦角和平均应力，第四章通过地震动力反应计算表明，LSI是结构周围地基抗震设计的较好指标，因为DSI比动力反应计算所反映的地基强度大，第五章是结论。

The purpose of this paper is to make clear the ground stability around tunnel structures in earthquake by using dilatational elastic strain energy generated in the ground and to find proper index for earthquake resistance of the ground around tunnel structures.In Chapter 1, the stability of earth materials under plane strain condition is discussed by using dilatational elastic strain energy When dilatational elastic strain energy in the ground reaches its maximum defined by cohesion, internal friction angle and mean stress of the ground, shear zone spreads in the ground. The direction of shear zone is decided by the dilatational angle and internal friction angle of the ground.In Chapter 2 and 3, the earthquake resistance of the ground around the box tunnel and shield tunnel is discussed by quasi-static analysis of elasto-plastic finite element method. Limit Seismic Intensity is defined as the time when shear zone connects between ground surface and upper parts of tunnels, as the seismic intensity increases. Aocording to FEM calculation, it is shown that LSI depends on cohesion, internal friction angle and mean stress of the ground.In Chapter 4, dynamic response calculation in earthquake shows that LSI is the good index for earthquake resistance design of the ground around structures, because DSI shows the largest intensity of the ground than in dynamic response calculation.The Chapter 5 is the conclusion.