考虑斜坡效应的地基水平抗力比例系数确定方法

水平地基抗力比例系数对桩基设计至关重要,基于平坦场地比例系数设计的斜坡基桩,常因忽视斜坡效应的影响而带来安全隐患。为研究斜坡效应对斜坡地基比例系数的影响,设计并完成了4组黏性土坡基桩水平静载模型试验,获得了0°、15°、30°及45°坡度下地基等效比例系数与地面处桩身水平位移曲线及桩顶荷载-位移梯度曲线等;建立了地基比例系数与坡度间的拟合关系式;对比分析了斜坡地基比例系数取值对基桩水平承载特性的影响。研究结果表明：黏性土坡地基比例系数随桩身水平位移增大而呈非线性关系减小,当地面处桩身水平位移小于6 mm时,地基比例系数急剧减小,而后减幅较小;基桩临界荷载和极限荷载均随斜坡坡度增加而减小,与平地相比,斜坡坡度每增加15°,基桩临界荷载和极限荷载约分别减小17%和16%;结合现有试验表明,斜坡坡度越大,地基比例系数越小;坡度每增加15°,对应的碎石土、砂土及黏性土坡地基比例系数m约分别减小38%、32%和31%;根据现有试验以及试验结果,建立了不同类型斜坡地基比例系数取值标准与斜坡坡度之间的经验关系,可为斜坡桩基设计提供参考依据。

Determination Method for the Foundation Horizontal Resistance Ratio Coefficient Under Consideration of the Slope Effect

The proportional coefficient of the horizontal foundation resistance is crucial for the design of the pile foundation. The pile in sloping ground is designed based on the proportional coefficient of the flat site, and often brings security risks because the influence of slope effect is ignored. To study the influence of the slope effect on the proportional coefficient of the slope foundation, four groups of horizontal static load model tests of piles in cohesive soil slope foundation were designed and completed. The horizontal displacement curves for the pile body and load-displacement gradient curves of pile top were obtained under a slope of 0°, 15°, 30°, and 45°; and the fitting relationship between the scale coefficient of the foundation and slope was established. The influence of the slope foundation ratio coefficient on the horizontal bearing characteristics of piles were also analyzed. The research shows that the foundation's proportional coefficient of cohesive soil slope decreases nonlinearly with the increase in the horizontal displacement of the pile. When the horizontal displacement of the pile at the ground level is less than 6 mm, the foundation proportional coefficient decreases sharply before decreasing slightly. The critical load and ultimate load of the foundation pile decreases with an increase in the slope gradient. Compared with the flatland, the critical and ultimate loads of the pile decrease by approximately 17% and 16% respectively for every 15° increase in the slope gradient. The existing tests show that the larger the slope gradient, the smaller the ratio coefficient. When the slope angle increases by 15°, the corresponding proportion coefficients m of the gravel soil, sand soil, and clay soil slope foundations, decreased by approximately 38%, 32% and 31%, respectively. Based on the existing test and the test results in this study, the empirical relationship between the value standard of proportional coefficient for different types of slope foundations and gradients was established, which can provide a reference for the design of the pile in sloping ground.