The second ship lock of Beijiang Mengli is situated in the interbedding of carbonaceous limestone,carbonaceous shale and siltstone,limestone or a mixing zone.We carry out the research on geotechnical problems including the stability of deep foundation pit,the stability of excavated slope higher than 60 m and intensive karst treatment.We also apply the integrated investigation technology including engineering geological survey,drilling,geophysical survey,in-situ test,laboratory soil tests,and new investigation technology such as shear test,tube wave testing,borehole TV,wave velocity testing to obtain much more reliable shear strength parameters for calculation of slope stability and degree of karst development.It can make a good base for Beijiang Mengli ship lock construction and provide the reference for the similar projects.