Influence Of Deep Excavation On Surrounding Buildings In Prosperous Urban Areas Where The Geological Conditions Were Bad

With the development of large, centralized city, people’s demands on underground structures such as city subways, underground garages, and underground supermarket are growing. This holds true in the demands on the excavation depth and support of foundation pit engineering. And many problems go along with deep excavation in prosperous urban areas, such as its influence on surroundings. People pay their attention mainly on the excavation and support of deep foundation pit and ignore its influence on the nearby buildings and environment.The geological condition of XX square station is poor, its water table is high. And it has short distances with surrounding buildings, especially with the exhibition hall whose distance with the nearest digging point is8.5m. For the foundation pit at square station, the entire length is161m, width of standard section is36m, main structure is a4-column5cross-frame structure, excavation depth is28m, and the maximum span is up to40.3m. The strata disturbance induced by excavation would cause surrounding ground surface settlement, which will threaten the surrounding buildings and underground pipelines. The earthwork and construction is difficult.This article, set in the foundation pit of square subway station, combined with complex geological condition of soft clay in the South, analyzed some problems in the excavation of deep foundation pit. Research content is as follows:(1) In light of the environmental, geological, hydrological and other conditions, reasonable construction methods and construction technologies were made in connection with major difficulties. And specific protection measures for buildings were also made after analyzing the interaction between foundation pit and its neighboring buildings.(2) In order to ensure the safety of the supporting structure and nearby buildings, and to provide a basis for the future influence of cover and excavation top-down station on adjacent buildings in bad geological condition, during the construction,20measuring points for monitoring were arranged near the exhibition hall and the monitoring data were analyzed. It can be seen from the settlement monitoring data that the sixth section of excavation, which is near the exhibition, had the biggest influence on the exhibition hall. And the second layer of the excavation caused the largest settlement, which was finally stabilized. There was an apparent differential settlement taking the exhibition hall as a whole, but which did not go beyond100mm. Thus construction requirements were meet.(3) A model was built by numerical simulation. The foundation excavations in the absence of piles and with piles were simulated and calculated respectively, and the calculation results were compared. After the reinforcing of the double rank jet grouting pile, when the excavation was complete, the horizontal and vertical displacements at the lower part of the exhibition hall were significantly reduced. This means the reinforcement of the double rank jet grouting pile could effectively control the horizontal and vertical displacements of the building. And the whole displacement vector of foundation pit close to the building was controlled significantly and tended to be even. Therefore, the reinforcement has played a significant role in the protection of the building. And from the map of damaged areas, it can be seen that the damaged areas did not run through, thus they could not cause harm to the building foundation.Through theoretical study, field monitoring and numerical simulation, it is considered necessary for the reinforcement of the foundation pit at the exhibition hall side. The exhibition hall was protected by the reinforcement of double rank jet grouting pile effectively. All of these also provide some theoretical basis for the future foundation pit excavation’s influence on surrounding buildings in prosperous urban areas.