凿井期冻结井外壁的力学模型及水平极限承载力研究

Mechanics Model and Ultimate Horizontal Bear Capacity of Outer Shaft Lining During Freezing Sinking

冻结井外壁浇筑后,受力状态逐渐由平面应力向广义平面应力转变,并承受急剧增长的冻结压力作用,因而确保早期水平承载力是外壁设计的关键.针对冻结井外壁的受力特点,分别基于两种混凝土强度准则,推导出了平面应力、广义平面应力、平面应变状态下外壁水平极限承载力的计算公式.研究表明:外壁水平极限承载力取决于井壁断面特征系数、混凝土应力状态、混凝土的单轴抗压强度;与平面应力状态相比,平面应变状态下外壁水平极限承载力显著提高.为确保冻结凿井工程的安全,外壁应尽量按平面应力模型或广义平面应力(如能确定值)模型而非平面应变模型开展设计,否则水平极限承载力将被显著高估.

Having been cast,the out shaft lining generally has a stress shift from plane stress to general plane stress and bears quickly increased freezing pressure.Therefore,it is vital to possess sufficient early bear capacity.According to mechanical characteristics of outer shaft lining during freezing sinking,formulas for calculating ultimate horizontal bear capacity of outer shaft lining,plane stress,and general plane stress.The analysis indicates that the ultimate horizontal bear capacity of outer shaft lining depends on such factors as crossing section parameters of the lining,stress status,and strength of concrete.The ultimate horizontal bear capacity of outer shaft lining increases obviously in plane strain state compared to that in plane stress state.In order to guarantee it's safety,outer shaft lining should be designed according to plane stress or general plane stress model(if can be determinated),other than plane strain model,otherwise,it's ultimate horizontal bear capacity could be overestimated.