Combined with the design practice in foundation excavation engineering

the problems for combined supporting from inner supports and composite soil nailing wall under binary geological conditions

including soil layers and rock stratum with weak intercalation in range of excavation depth

are analyzed.These problems mainly include the following: calculation model of earthen pressure

the local bearing capacity of foundations below steel pipe piles

stiffness coordination at the junction of rigid and flexible supports

internal bracing stability influencd by restrained condition of upright post

etc.Problems of concern for design of similar foundation pit supports are pointed out

and measures for solving these problems are proposed.All these can provide references for similar projects.