岩石地基挖孔基础承载特性试验研究

Tests on Uplift Behavior of Rock Socket Foundation

为研究岩石地基挖孔类基础的上拔承载特性及影响规律,开展了不同埋深、立柱直径和扩径率的直柱型和扩底型挖孔基础的试验研究。试验结果表明,岩石地基挖孔基础上拔承载力与地基–基础接触侧面积的线性正相关。因此,以桩基规范为代表的嵌岩桩上拔承载力计算模型具有合理性。混凝土效率与立柱直径负相关,与基础埋深和扩径率正相关;但扩径率对混凝土效率的影响存在临界现象。在岩基挖孔基础工程设计中,建议采用扩底型挖孔基础,扩径率可取为≥2.0;并优先通过增加基础埋深的方法来提高基础设计承载力。4.5倍深径比范围内,并未发现岩基挖孔基础存在临界埋深现象。

In order to study the uplift behaviors and sensitivity of rock foundation under uplift load,load tests on straight shaft type and belled type rock socket foundations with different buried depths,shaft diameter and belled-butt diameter were carried out.Test results show that there is a positive linear correlation between the uplift capacity of rock socket foundation and the foundation-rock contact area.Therefore,the calculation model of uplift capacity of rock socket foundation represented by pile foundation code is more reasonable.The uplift capacity to the foundation volume ratio is negatively correlated with the shaft diameter,and positively correlated with the foundation depth and diameter enlargement.However,the uplift capacity to the foundation volume ratio is not obviously influenced until enlargement to shaft diameter ratio is greater than a critical value.In the design of rock socket foundation,belled foundation with enlargement to shaft diameter ratio≥2.0 is recommended;and it is of top priority to increase the foundation depth to increase the uplift capacity of rock socket foundation.In the range of 4.5 times depth to diameter ratio,no critical buried depth was found for rock socket foundation.