斜坡地基挖孔基础水平承载特性现场试验研究

Field Test on Horizontal Bearing Characteristics of Shafts in Slope Ground

以输电线路工程中常用的扩底形和直柱形原状土基础为研究对象,通过开展斜坡地基条件下水平荷载工况的现场静载试验,对比分析了直柱形和扩底形基础在荷载—位移曲线、地基承载力、界面土压力分布以及地基土体破坏模式等方面的差异。试验结果表明:两种结构形式的试验基础水平承载—位移曲线、水平荷载—转角曲线整体呈缓变形即"直线—曲线—直线"三阶段变化趋势,而两者之间的差异在于荷载—转角曲线在临近曲线段末尾处突然发生翘起;相较于直柱形基础,扩底的设置增加了基底的抵抗力矩,同时降低了基础旋转中心位置,使得扩底形基础承载力较直柱形得到了提高;两种形式基础侧壁土压力均沿深度方向呈抛物线形分布;基础发生破坏时,两种形式基础在临近下坡侧均出现大量羽状裂缝,并伴有地基土隆起,扩底的设置使得基础对周围土体的影响深度和范围均增加。

The paper took the straight shaft and belled shaft with different structure types as research objects,horizontal field tests of two test shafts in slope loess ground located at Yuzhong Town,Gansu Province were carried out. Load displacement curve,horizontal bearing capacity,soil pressure and failure mode of two types of shafts were analyzed. The test results show that the horizontal load displacement curves and horizontal load rotation angle curves of the two types of shafts are all slowly changed,and take on obvious＂straight line-curve-straight line＂three stages; compared with that of the straight shaft,horizontal bearing capacity of belled shafts is increased obviously because the resistance moment acted bottom of the shaft is increased and the rotation center position is reduced simultaneously due to enlarge head setting; The soil pressure of shaft soil interface presents parabola change with depth adding. In the failure stage,there appears a large number pinnate fracture on the downhill side of the ground and failure range around belled shaft is larger than that of straight shaft due to enlarge head setting.