主被动状态间墙体侧向位移与土压力关系

Relation of Wall Displacement-earth Pressure from Active to Passive State

为了研究从静止到主动状态或从静止到被动状态下墙体侧向位移与墙背土压力大小的关系,以应力Mohr圆为出发点,通过引入内摩擦发挥角,推导了主动与被动状态间土压力与内摩擦发挥角的统一表达式。根据所构建的墙体位移与土体剪应变几何方程以及等极限应变下的剪应变-剪应力理想非线弹塑性物理模型,建立了能基本反映土体应力-应变特性和墙后填土初始应力状态的墙体位移-土压力统一函数关系式,并结合Coulomb土压力模型近似考虑了墙背与填土间摩擦力的影响。研究结果表明:影响墙体位移-土压力关系的核心要素是墙背初始应力状态、墙后滑移区范围及填土应力-应变特性;初始侧压力系数的增加,直接导致进入主动与被动状态所需墙体位移出现相应的增大和减小,墙体位移-土压力曲线沿水平轴呈现出整体平移的变化;土体内摩擦角和墙土摩擦角的改变会引起滑移区范围的变化,从而使墙体位移-土压力曲线整体放大或缩小;填土应力-应变特性是墙体位移-土压力关系的微观本质,其模量比与极限剪应变对墙体位移-土压力曲线的平缓程度及极限状态下的墙体位移大小影响显著。

The amplitude of earth pressure either from the initial to active state or to passive state was closely linked with the amount of wall displacement and earth pressure. Based on Mohr circle of stress, the expression between earth pressure from active to passive state and mobilized angle of shearing resistance was derived. According to the established geometric equation of soil shear strain and wall displacement, and the corresponding nonlinear elastic-perfect plastic model between soil shear strain and shear stress under the equal ultimate strain, the equation of the wall displacement and lateral earth pressure was established considering the influence of soil stress- strain behaviors and initial stress state of the backfill. Besides, the equation was also revised to reflect the influence of interface friction between the wall and backfill based on Coulomb earth pressure model. The results show that the major factors affecting wall displacement-earth pressure relation are the initial stress state of the backfill, the slip region, and the soil stressstrain behavior. The required wall displacement increases for reaching active state, and decreases for reaching passive state, with the increase of the initial lateral earth pressure coefficient, making the wall displacement-earth pressure curve move horizontally. The soil＇s internal friction angle and interface angle between the wall have a significant influence on wall displacement-earth pressure curve by changing the active and the passive failure zone behind the wall. The soil stress-strain behavior is microscopic embodiment of the relationship between wall movement and earth pressure, whilst the shape of wall displacement-earth pressure curve and abscissa interval range of wall displacement in the ultimate state are controlled by the soil modulus index and the ultimate shear strain.