深基坑单支点挡土结构稳定性之讨论

Discussion on the stability of single support retaining structure in deep foundation pit

对单支点支挡结构的倾覆稳定性和踢脚稳定性进行了理论上讨论,并通过工程实例分析,采用《北京理正深基坑支护结构设计软件》结合手算,得出在满足规范要求的各项稳定性的情况下,仍然有必要对支挡结构底端的抗倾覆稳定性进行验算,并由抗倾覆稳定性验算得出的支点力与弹性支点法得出的支点力进行比较后取大值作为后续支撑体系的设计荷载较为合理。规范中支点以上土压力作为不利荷载考虑不太合理,尤其是在支点下落较大时,对单支点支挡结构的踢脚稳定性影响较大,造成了支护费用造价浪费。支点以上的主动土压力是有利荷载,可以作为安全储备,采用在Ma中扣除Ma1的踢脚稳定性安全系数K2进行嵌固深度验算更合理些。

The paper is related to the theoretical discussion on the overturning stability and skirting stability of single support retaining structure,adopt the Beijing Lizheng Deep Foundation Pit Support Structure Design Software combined with manual calculation.Through the analysis of engineering examples,it is concluded that checking the overturning stability of the bottom end of the retaining structure is still necessary even if various specified stability requirements satisfied,and it is more reasonable to take the larger one after comparing the support force obtained from the anti-overturning stability checking with the support force obtained from the model of elastic brace as the design load of the subsequent support system.It is unreasonable to consider the earth pressure above the support as an unfavorable load in the specification,especially when the support falls greatly.It has a great impact on the skirting stability of the single support retaining structure,resulting in a waste of support cost.The active earth pressure above the fulcrum is a favorable load,which can be used as a safety reserve.It is more reasonable to deduct the safety factor K 2 of M a1 from M a for checking the embedded depth.