Abstract:

In the design of pit support structure, the design of the pit-in-pit had a direct impact on security and economy of the support structure. Furthermore, a few of the excavation support structure accidents were closely related to unreasonable design of the pit-in-pit. Taking a soil nailing wall instability for example, the fundamental reason for the crash of the excavation support structure was analyzed. The method of reinforcement design was developed; but also the design method of the pit-in-pit was put forward. Mutual control and mutual influence between the foundation pit and the pit-in-pit were studied. Research shows that: the pit-in-pit of the basement foundation pit has a greater impact on the whole stability of the support structure; while the foundation pit support has a relatively smaller impact on the internal forces of the supporting piles in the pit-in-pit.

Key words: foundation pit, pit-in-pit, the whole stability, steel sheet pile