土中中风化嵌岩抗拔桩承载机理研究

Bearing Mechanism of Moderately Weathered Rock-socketed Uplift Pile in Soil

根据某工程中风化嵌岩抗拔桩自平衡静载原位试验,对试验数据进行简要分析,结合该工程地质条件,选择合理的岩土力学参数和试验数据,建立了合理嵌岩抗拔桩FLAC3D数值分析模型。运用所建立的数值模型对3根抗拔桩进行自平衡试验直至破坏,确定了各桩的极限承载力,并且研究了同一条件下不同嵌岩深度对抗拔桩的极限承载力的影响及抗拔桩桩侧阻力、桩身轴力随外荷载的变化情况。研究结果表明:①风化岩石地区建立模型时,岩石剪切模量及体积模量需要按试验换算值折减到1/10左右,才可建立合理的数值模型;②嵌岩抗拔桩的极限承载力主要受嵌岩深度的影响,同一条件下,嵌岩抗拔桩极限承载能力随嵌岩深度、桩长增加而增大,且桩设计时其嵌岩深度不宜太小;③随着埋置深度的增加,桩侧阻力先增大后减小,桩中间侧阻力对极限抗拔承载力贡献最大;④抗拔桩的桩径对极限承载力具有尺寸效应。

According to in-situ self-balancing static loading test of uplift pile in moderately weathered rock,a FLAC 3D numerical analysis model of rock-socketed uplift pile is established based on reasonable rock mechanics parameters and test data together with the geological condition of the project.By using this model,three uplift piles undergone self-balancing test until failure were simulated to determine the ultimate bearing capacity of each pile and to further examine the influence of rock socket depth on the ultimate bearing capacity of uplift pile and the variations of lateral resistance and axial force of pile with external load.Results demonstrate that:(1)The shear modulus and volumetric modulus of rock should be reduced by 1/10 of test values when building a rational numerical model.(2)The ultimate bearing capacity of rock-socketed uplift pile is mainly affected by the socketed depth of rock.Under the same condition,the ultimate bearing capacity of rock-socketed uplift pile increases with the socketed depth of rock and the length of pile,and the rock-socketed depth of pile should not be too small.(3)With the increase of rock-socketed depth,the side resistance of pile increases first and then decreases,and the middle resistance of pile contributes the most remarkably to the ultimate bearing capacity.(4)The diameter of uplift pile has size effect on ultimate bearing capacity.