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

本文的目的是利用地表产生的膨胀弹性应变能来研究地震作用下隧道结构周围地面的稳定性，寻找合适的隧道周围地面抗震指标。在第一章中，利用膨胀弹性应变能讨论了平面应变条件下土体材料的稳定性，当地面的膨胀弹性应变能达到最大值时，地面的粘聚力、内摩擦角和平均应力定义了剪切带在地面中的扩展。剪切带的方向由地基的扩张角和内摩擦角决定。第二章和第三章采用弹塑性有限元拟静力分析方法讨论了箱形隧道和盾构隧道周围地基的抗震性能。极限地震烈度是指随着地震烈度的增加，地表和隧道上部之间的剪切带连接的时间。第四章地震动力反应计算表明，由于动力反应计算比动力反应计算更能反映地基的最大烈度，因此对于结构周围地基的抗震设计而言，动力反应计算是一种较好的指标。

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.