Micro-piles have been widely used in excavations due to their convenience and simplicity in construction. Taking a certain rock foundation pit supported by combination of micro-steel-pipe piles and rock bolt support for example

supporting mechanism of the micro-steel-pipe piles is analyzed by numerical simulation. Analytical results have indicated that when thick strong weathering rock or weak rock layer exists

the micro-steel-pipe piles embedded in it can effectively decrease the horizontal displacements of the foundation pit and adjust the tension in the prestressed anchor cables; while the micro-piles can bear notable bending moment and axial compressive force. Micro-steel-pipe piles constructed in strong weathering rock layer should be considered for supporting structure design of the rock foundation pit

and capacity of the micro-piles under bending moment and compressive force should be verified. When the micro-steel-pipe piles were constructed in integrated and hard rock layers

such as intermediate or weak weathering rock layers

the micro-piles had hardly any effect on excavation of the foundation pit; so for this situation the micro-piles can be cancelled.