深基坑空间效应机理及考虑其影响的土应力研究

Mechanics of deep excavation's spatial effect and soil pressure calculation method considering its influence

以坑周土体为研究对象,根据土体中土拱效应及滑裂面的相对位置关系分析深基坑工程空间效应的形成机理;根据受空间效应影响土体微元和不受空间效应影响土体微元的应力状态,推导考虑空间效应的支护结构土正应力计算公式.研究表明:空间效应的本质为坑周土体中的拱效应对支护土正应力和变形等特性的影响,研究空间效应时采用基坑长深比更合理;考虑空间效应的土正应力计算公式可以精确地计算支护结构上某点处的土正应力值,是关于该点深度和至坑角距离的二元函数,弥补了基坑设计规范中土正应力计算公式只与深度相关的缺陷.算例表明,该公式可以反映支护结构上土正应力的整体分布情况.

Taking the soil body around the deep excavation as subject investigated, according to the posi- tion-relationship between soil arching and slip plane, the forming mechanics of deep excavation＇s spatial effect was analyzed. According to the stress states of micro soil elements affected and not affected by the spatial effect, an earth pressure equation considering spatial effect was derived. Studies show that the es- sence of spatial effect is the influence of soil arching around excavation to the characteristics of earth pres- sure and support deformation, and it＇s more appropriate to take the ratio of length to depth when researc- hing spatial effect. The earth pressure equation considering spatial effect can calculate the earth pressure at different position on the support precisely. The equation has two variables related to position＇s depth and distance to excavation corner, covering the shortage of earth pressure equation only related to depth in code of excavation design. An example analysis shows that the equation can to reflect the earth pressure＇s distri-bution condition of the retaining structure.