单桩承载力分项系数的分析

目的从概率设计出发,探索评价桩基可靠度的简单模式,使之能够应用于实际工程.方法根据桩基的承载机理,对单桩分项系数与总安全系数的函数关系进行理论分析.结果由于分项系数受桩型、桩侧与桩端土的性质、桩的长径比的影响,在单桩极限承载力总安全系数确定的情况下,分项系数不可能唯一确定.同时,由于分项系数间的函数关系,只要确定其中之一,另一个也随之确定.结论采用固定的分项系数,总安全系数总是被降低或提高.因此采用以单桩承载力特征值定义的单一安全系数还是满足工程需要的.总安全系数确定,分项系数的取值对安全度没有影响.

Analysis on Partial Factor of Single-pile Bearing Capacity

In order to analyze the function relationship between partial factor and the overall safety factor on condition that the overall safety factor is ensured,the function relationship between single-pile partial factor and overall safety factor is analyzed in theory,based on the pile foundation's bearing mechanism.Because partial factors are affected by pile type,soil around pile and under the pile end and ratio of length to diameter,when the overall safety factor was ensured,partial factor can't be ensured single.In the meantime,because of the function of the partial factors,if one is ensured,the other must be ensured.It is analyzed that overall safety factor must be reduced or increased if the unvaried partial factor is adopted.It can meet the engineering demands by using characteristic value of single-pile bearing capacity.The value of partial factors cannot affect the reliability if the overall safety factor is ensured.