在现行规范中，沿缓倾外倾软弱结构面滑动的边坡主动岩石压力Eak公式未考虑后缘裂隙水压力，导致Eak计算存在偏差。针对这一问题，考虑后缘裂隙水压力，根据力系的平衡关系和几何条件，进行受力分析和简化，推导主动岩石压力计算公式，判断是否存在极值点以及其位置。研究结果表明，与不考虑后缘裂隙水压力相比，Eak的误差达到21.89%～100%；Eak在有实际工程意义区间内存在极大值。针对缓倾岩层倾角θ 和结构面内摩擦角φ 大小进行讨论，当θ >φ 时，坡顶潜在滑裂面宽度b0一般为边坡高度H 的0.2～1.2倍；当θ ≤ φ 时，Eak的极大值出现在坡面位置。本次研究分类完善了计算公式，并对极值点位置和H 等因素之间的关系进行了分析，对沿缓倾软弱外倾结构面滑动边坡的防治具有理论和工程实践意义。In the current code

the Eak formula for activerock pressure of slopes sliding along gently inclined outward weak structuralplanes does not consider the water pressure of the trailing edge fractures

which leads to deviation in Eak calculation. In viewof this problem

according to the balance relationship and geometric conditionsof the force system

the stress analysis and simplification are carried outconsidering the water pressure of the trailing edge crack

and the calculationformula of the active rock pressure is derived to determine whether there is anextreme point and its location. The research results show that the error of Eak is 21.89%-100% without considering water pressure; Eak has a maximum in the effective range. The dip angle ofgently inclined rock stratum θ and the friction angle in the structural plane φ are compared

it is found that if θ >φ

the width of potential slip surface at the topof slope is generally 0.2-1.2 times of the slope height H; and if θ ≤ φ

the maximum value of Eak appears on the slope. This study improves thecalculation formula by classification

and analyses the correlation between theextreme point position and some factors including H. It is of theoretical and practical significance for theprevention and control of sliding slope along gently inclined soft outwardinclined structural plane.