季节冻土地区深基坑桩锚支护体系安全性研究

Study on the security of a ultra-deep foundation pit with the pile-anchor support structure in the seasonal frozen earth

通过对某越冬深基坑工程的现场监测,分析了基坑工程水平变形情况,研究了冬季基坑水平变形的原因.监测结果表明:桩锚支护超深基坑水平位移已超过现行地方规定,但支护体系的安全性仍可满足要求,应进一步结合该地区其他超深基坑的监测结果分析,提出该地区桩锚支护体系安全预警指标;冻融循环会引起锚索预应力损失,使桩锚支护超深基坑产生较为明显的水平位移,影响基坑安全.因此,在越冬基坑设计和施工组织等方面,应综合考虑坑壁保温、地表排水和桩后土体排水等问题,降低冻融循环的不利影响.

Through on-site monitoring methods for the pit,the current cttsplace,,~ overwinter displacement of pit were studied. The results show that the horizontal dis- placement of ultra-deep pit with pile-anchor program is beyond the present locality code,but its security is suitable. Therefore,a new security index of this pit must be put forward to monitoring the result of other pits. The anchor prestressing is lost by freeze- thaw ,and the horizontal displacement of pit is obviously increased and the security of pit is effected. The overwinter pit must be studied to reduce disadvantages during the de- sign and construction. For example, the heat preservation of slope,could be done, and draining water could be removed from soils on the backside pile and on the surface of the earth.