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静压桩瞬时终压力与极限承载力是不同的概念,从沉桩过程和承载力时间效应两个方面出发,对两者相关关系的机理进行研究,并提出了侧阻退化系数和时间效应系数的概念;基于静载试验的Q–S曲线,采用灰色理论对未达破坏标准的试验桩进行极限承载力的修正,修正值的提高幅度随静载试验最终沉降的增大而减小;对近2000根静压混凝土管桩的实测数据进行研究,并与其它地区的相关资料展开对比。分析发现承载力与终压力比值(压力比)的概率点呈F分布,压力比随长径比的增加呈双曲线型增长,回归分析得出不同地质条件下的函数表达式。持力层为黏性土时压力比随长径比的增长幅度明显大于其它土层,而在持力层和长径比相同的情况下,桩侧为粉土时的压力比值通常大于黏性土和软土。桩身较短时极限承载力可能小于终压力,主要归因于压桩结束后桩端土体的回弹和应力的释放。
Static pressure pile instantaneous ultimate pressure and ultimate bearing capacity are different concepts from the pile driving process and bearing capacity time effect of two aspects of the relationship between the two mechanisms to study and put forward the lateral resistance degradation coefficient and the time effect coefficient Based on the Q-S curve of static load test, the gray theory is used to correct the ultimate bearing capacity of the test piles that have not reached the failure criterion. The increase of the correction value decreases with the increase of final settlement of the static load test. Nearly 2000 pieces of measured data of the hydrostatic concrete pipe pile are studied and contrasted with the relevant data of other areas. The analysis shows that the probability point of the ratio of bearing capacity to the final pressure is in the form of F distribution, and the pressure ratio increases hyperbolicly with the increase of the aspect ratio. The regression analysis shows the function expression under different geological conditions. When the bearing layer is clayey soil, the pressure ratio increases with the aspect ratio obviously more than other soil layers. However, under the condition of the same holding layer and the same aspect ratio, the pressure ratio of pile side to silt is usually greater than the viscosity Soil and soft soil. When the pile body is short, the ultimate bearing capacity may be less than the final pressure, which is mainly attributed to the rebound of the pile body and the release of stress after the piling.