考虑容许沉降影响的群桩抗力系数和安全系数的可靠度设计

RELIABILITY-BASED DESIGN OF RESISTANCE FACTOR AND SAFETY FACTOR FOR PILE GROUP SYSTEM CONSIDERING LIMITING TOLERABLE SETTLEMENT

利用单桩可靠度设计方法,考虑群桩效应和系统效应的影响,提出基于沉降控制条件的群桩抗力系数和安全系数的可靠度设计方法。研究了土体性质、桩型、承台、系统效应和容许沉降等因素对群桩抗力系数和安全系数的影响。结果表明:群桩抗力系数随系统效应系数的增大而增大,系统效应越强,可采用较高的抗力系数进行群桩可靠度设计;群桩抗力系数随容许沉降的增加而增大,但增长幅度逐渐减小,随容许沉降条件的放宽,群桩抗力系数设计依赖于承载力因素而非沉降因素;无黏性土、低承台条件下群桩抗力系数设计值大于黏性土、高承台条件下群桩抗力系数设计值;安全系数随系统效应系数的增大而减小,随容许沉降条件的放宽而降低。

According to the reliability design method of single piles and taking into account pile group effstiidy presented the reliability design methiod for the resistance factor and safety factor of pile group based quirements. Meanwhile, it is studied the impact of soil properties, pile types, pile cap types, system effect, and tlement on the resistance factor and safety factor of pile group. The following conclusions can be drawn from the resistance factor of pile group increased witli the system fect factor. The large resistance factor can be accepted for the reliability de-sign of pile group when there existed the strong system ] fect . Second, the resistance factor of pile group increased witli the limiting tol -erable settlement altliough the increase rate graduaiy diminished. Withi softening the limiting tolerable settlement requirements the re-sistance factor design of pile group depended on the bearing capacity requirements rathier design resistance factor of pile group under the condition of cohesionless soils and ground contact caps was larger than that under the condition of cohesive soils and freestanding caps. Finaiy, the safety factor of pile group decreased witii the system efect factor and re-duced witii softening the limiting tolerable settlement requirements.