由岩溶塌陷、隧道开挖等方面引起的土体变形往往会对基础建设和基础结构等造成不均匀沉降、地面塌陷及开裂等危害，确定土体结构顶部松动土压力的分布情况并准确地分析土体变形与土拱效应间关系显得尤为重要。为了揭示土体变形和沉降对结构顶部松动土压力的变化规律，进行了一系列不同H/B 的活动门试验（H 为地基高度，B 为活动门宽度）。基于试验结果

提出以三角形作为力学模型分析不同滑移面时松动土压力的数学模型，考虑了滑移面角度与土体变形及主应力偏转三者之间的关系，分析了滑移面内任意水平微分土条的主应力偏转情况并建立受力平衡微分方程，根据不同滑移面形态下的边界条件求解松动土压力理论公式，与已有试验结果对比验证了理论公式的合理性。通过对滑移面角度、侧向土压力系数和内摩擦角等主要参数进行分析，结果表明：在较小相对位移下（1%～3%）土体应力迅速发生转移和重分布，初始滑移面角度略小于π/4+ φ /2（φ为内摩擦角），随着H/B 增大土体应力比缓慢增长最终趋于稳定；地基内封闭三角形滑移面的松动土压力与相对位移及内摩擦角相关；内摩擦角的增加使得土拱效应得到充分发挥，加强了应力转移，降低了土拱应力比；内摩擦角的增大减小了水平向应力分量，从而降低了侧向土压力系数。Soil deformation caused by karst collapse andtunnel excavation often causes uneven settlement

ground collapse and crackingof foundation construction and foundation structure. Development of approachesto determine the distribution of loose earth pressure at the top of soilstructure and analyze the relationship between soil deformation and soilarching effect accurately is of much importance. A series of classical trapdoortests with different H/B ratios were conducted to reveal thevariation law of soil deformation and settlement on the loose earth pressure atthe top of the structure. Based on the test results

a mathematical model isproposed to analyze the loose earth pressure with triangle as the mechanicalmodel under different slip surfaces. The relationship among the slip surfaceangle

soil deformation and principal stress deflection is considered. Theprincipal stress deflection of any horizontal differential soil layer in theslip surface is analyzed and the stress equilibrium differential equation isestablished. The theoretical formula of loose earth pressure is solvedaccording to the boundary conditions under different slip surfaces. Therationality of the theoretical formula is verified by comparing with thetrapdoor tests results. The main parameters (e.g. slip surface angle

coefficient of lateral earth pressure and internal friction angle) wereanalyzed. The results reveal that when the displacement-width ratio (1%−3%) issmaller

the stress rapidly transfers and redistributes

and the angle ofinitial slip surface is slightly smaller than π/4+φ /2. With the increase of H/B

the vertical stressincreases slowly and finally tends to be stable; loose earth pressure of closedtriangular slip surface in foundation is related to the displacement-widthratio and internal friction angle; the increase of internal friction anglemakes full use of soil arching effect

strengthens stress transfer and reducesvertical stress; the increase of internal friction angle brings a remarkablereduction in the horizontal stress component

thereby reducing the lateralearth pressure coefficient.