Abstract: Combined with a building foundation pit of Nanchang, the retaining and protecting structure of foundation excavation, the horizontal displacement, the settlement monitoring points’ disposal, observation methods and monitoring data processing, are described. Based on the results of monitoring, it would forebode the danger, estimate the safety of engineering and avoid the happening of engineering accident.The construction was supervised with the monitoring results; and the information feedback was optimized designed.There were groundwater inflow and sand inflow due to the abundance of groundwater after the excavation, which made the deeper part such as the elevator shaft pit can’t be excavated to the right location. A method that is forming a waterproof wall around the elevator shaft pit and back covering the bottom of well with jet grouting was brought forward for the limited drainage ability around the excavation. The results show that the elevator shaft pit could be excavated uprightness one day after the construction of jet grouting and there was not water yielding, which brought on favorable reinforced effect and economy benefit.

Key words: excavations, deformation monitoring, groundwater, jet grouting