In the simulation and analysis on culvert construction , the method of foundation - pit excavation layer by layer and step by step was used , i . e . the method that makes the surface of excavation have no stress , when the elements were excavated gradually in period of construction . at this process , the state of soil is unloading , the laws of stress field and displacement field with the depth of excavation were studied . based on the obtained stress field and displacement field after the excavation was completed , by using of the newly increased filling - elements " gravity and the grinding force , the simulation of the construction of body of the culvert and foundation - pit ' s filling layer by layer had also been done in this dissertation 用有限元法模拟分析涵洞基坑开挖时，采用分层、分步模拟开挖过程的方法，即将计算域内单元分层“挖去” ，使开挖表面成为无应力表面的方法，分析土体在卸载状态时的应力场和位移场随开挖深度的变化规律；在洞体施工后，回填土体时，据开挖完成时的应力场、位移场，通过逐级增加计算域内的单元数目，施加每级新增加单元的自重荷载，利用有限元法模拟基坑及上覆土体分层填筑的施工过程，这不仅反映土体处于再加载应力状态时，填土受力及变形的一般规律，而且这种将地基? ?涵洞? ?土体作为一个统一整体进行模拟的方法，量化了三者之间的相互作用关系。
