基于抗滑桩内力计算方法——“m”法的桩顶最大位移判据研究

On the maximum displacement criteria for the pile tip-top based on “m” method for the internal force calculation of the anti-slide piles

针对陕西省高速公路沿线抗滑桩治理的滑坡,进行桩顶位移预警判据研究。基于抗滑桩内力计算方法——"m"法,通过给定桩顶位移,反算滑坡推力,进而求出桩身最大弯矩。计算得到的推力考虑了桩前土体抗力和桩间距的影响,因此悬臂桩和埋入式桩均适用。经过大量试算拟合得出不同地基系数K、地基系数随深度增加的比例系数m、锚固段长度、悬臂段长度及桩径下,桩顶位移与桩身最大弯矩的关系式。该式适用于桩径为2 m×3 m、1.5 m×2 m的弹性桩。引用前人实例验证了公式的合理性,公式由初等函数组合而成,易于应用到预警系统中。今后针对具体抗滑桩设计方案,输入相关参数,可得到桩顶最大位移判据。

The present paper is intended to make an exploration of the stability of the landslide supported by the anti-slide piles along the newly-built highways in the Province of Shaanxi,from the point of view of the early warning criteria for their top displacement. It is just from the said point of view that we have done the back-sequential calculation based on the internal force calculation method of anti-slide piles named ＂m＂method whereas the thrust of the landslide and the maximal bending moment of the pile have been worked out by giving the top displacement of the piles,with the concrete strength grade of anti-slide piles being C30. In addition,the landslide thrust situation can be divided into three forms,that is,the rectangular form,the triangle form and the trapezoid one. And,then,we have established the relationship between the top displacement of the anti-slide piles and the maximum bending moment through a series of tentative calculations based on the foundation coefficient,the proportional coefficient of the foundation coefficient which proves to be increasing with the increase of the depth,the anchorage length,the cantilever length and the pile diameters. Furthermore,in the practical engineering application,it is also easy for us to work out the maximum bending moment of the pile body or bodies by reinforcing the calculation results for the drawing preparation of the anti-slide piles in reference to the rationality of the formula verified by the previous examples. For instance,the resistance given by the soil mass in front of the pile and the distance between the piles are also to be taken into account so that the cantilever piles and the embedded piles are both to be made satisfactorily applicable and wellsuitable. That is to say,the formula should be absolutely suitable for the elastic piles whose diameters ought to be equal to 2 m × 3 m and 1. 5 m × 2 m,which has to include all the elementary needed functions to be expected to play in the early warning system. What is more,the goal of our future research should be oriented to input the correlation parameters and achieve the maximum top displacement criterion of pile in the corresponding design scheme of the concrete anti-slide piles. Based on the aforementioned monitoring data,it would be easy and realistic to establish the future early warning and forecast of the stability of landslides through the above mentioned items of the innovative improvements.