注浆微型钢管桩体抗弯力学性能

基于15根注浆微型钢管桩体的抗弯荷载试验,综合分析钢管直径d和壁厚t、浆体水灰比W、钢管表面布孔直径r和间距s等因素对注浆微型钢管桩体抗弯承载特性、变形和破坏特点的影响。结果表明:相同桩径时,钢管直径和壁厚对微型钢管桩体抗弯承载特性影响显著,桩体极限抗弯荷载值随钢管直径和壁厚的增加近似呈线性增加; 当0.59≤d/D≤0.72(D为桩径),浆体水灰比在0.45～0.75之间时对桩体极限抗弯荷载的影响较小,钢管表面布孔形式对桩体极限抗弯荷载的影响较小; 基于注浆微型钢管桩外包浆体和钢管的荷载-应变曲线分析可知,注浆微型钢管桩体抗弯破坏标准可以以外包浆体的破坏为准; 当0.28≤d/D<0.59时,钢管屈服和受压区外包浆体开裂所对应的抗弯荷载与极限抗弯荷载基本相同,而当0.59≤d/D≤0.72时,荷载加至极限抗弯荷载80%时钢管屈服,注浆微型钢管桩体呈现出明显的延性特征,钢管及内核注浆体自身强度发挥充分且抗弯承载作用明显,建议实践中微型钢管桩体钢管设计时以0.59≤d/D≤0.72为宜。

Flexural Mechanical Properties of Grouted Micro-steel-pipe-piles

On the basis of flexural loading test for 15 micro-steel-pipe-piles, the effect of diameter d and wall thickness t of steel pipe, water cement ratio of slurry, diameter r and spacing s of steel pipe surface grouting holes on the flexural bearing capacity, deformation and failure properties of micro-steel-pipe-piles were comprehensively analyzed. The results show that with the same diameter of pile body, the diameter and wall thickness of the steel pipe have a significant influence on the flexural bearing capacity of the micro-steel-pipe-piles. With the increase of the diameter and wall thickness of steel pipe, the ultimate flexural load of micro-piles increases approximately linearly. When 0.59≤d/D≤0.72(D is pile diameter), the water cement ratio of the slurry changes between 0.45 and 0.75, the influence on the ultimate flexural load of the pile is small, and the influence of hole arrangement on the ultimate flexural load of piles is small. Based on the analysis of the load-strain curves of the grouted micro-steel-pipe pile and the surrounding slurry, the standard of the flexural failure of the piles is based on the damage of the surrounding slurry. When 0.28≤d/D<0.59, the flexural loads corresponding to steel pipe yielding and outside slurry cracking almost equal to the ultimate flexural load. When 0.59≤d/D≤0.72, the steel pipe at midspan begins to yield when the applied load is about 80% of the ultimate load, and the micro-steel-pipe-piles exhibit well extensible performance. The strengths of steel pipes and slurry inside pipes have been utilized fully and they can play main role against flexural performance of micro-piles. It is suggested that 0.59≤d/D≤0.72 should be used in the design of micro-steel-pipe-pile.