管桩水泥土复合基桩承载性能试验研究

Experimental Study on Bearing Properties of tubular Cement Composite Pile

管桩水泥土复合基桩是由高喷搅拌水泥土桩与同心植入的高强预应力管桩优化匹配复合而成的一种新型基桩。基于足尺模型试验研究了管桩水泥土复合基桩在竖向荷载作用下的承载性能,并与泥浆护壁钻孔灌注桩作了对比分析。试验结果表明:管桩水泥土复合基桩兼有桩身材料强度高、侧阻力大的优点,承载力较相同尺寸的钻孔灌注桩提高40%以上,单位承载力造价降低约35%;荷载传递规律兼有刚性桩与半刚性桩特性;桩侧阻力约为钻孔灌注桩的1.8倍;高强预应力管桩——水泥土界面粘结力发挥度为6.9%～15.7%,能够保证高强预应力管桩与外围高喷搅拌水泥土有效复合共同承担外部竖向荷载。最后指出管桩水泥土复合基桩设计的重点之一是桩头与高强预应力管桩底端处的材料强度验算。

Tubular composite pile made up of jet-mixing cement and PHC with core concrete （CPCP） is a new kind of piles. The CPCP consists of external jet-mixing cement-soil pile and PHC in the inner core which are optimal matched. On the basis of full-scale model tests, the bearing properties of CPCP under vertical loads are analyzed and compared with that of bored slurry support cast-in- place pile. The results of tests show that CPCP has the advantages of high material strength and high side resistance. Ultimate vertical bearing capacity of CPCP increases by more than 40% compared with bored cast-in-place pile in same size, and engineering cost decreases by 35%. Load transfer law of CPCP has the characteristics both of rigid pile and semi-rigid pile. Side resistance of CPCP is about 1.8 times of bored cast-in-place pile. The exerting degree of bond force between PHC and cement-soil is 6.9%~15.7%, which can ensure effective compound of PHC and jet-mixing cement-soil pile to bearing the vertical load together. Checking calculation of material strength of CPCP both in pile head and at the bottom of PHC is one of the key points of design of CPCP.