| At present,the support of subway foundation pit mostly adopts the method of underground continuous wall + internal support.It has the characteristics of large rigidity,good overall watertightness,and is suitable for areas with more complicated geological types,but at the same time,the cost is relatively high.The support can take different forms according to different geological conditions,so the selection of support design should be more cautious.The article relies on the deep foundation pit support project of Licun Station of Foshan Metro Line 3,aiming at the underground diaphragm wall + horizontal internal support Supporting system,through the deep foundation pit engineering site excavation monitoring data,preliminary design.The following conclusions are drawn through the research of the above content:(1)By analyzing the variation characteristics of the horizontal displacement of the ground connecting wall,and the wall deformation appears The rule is large in the middle and small at the two ends;the supporting axial force borne by the supporting system gradually increases with the continuous excavation of the foundation pit soil,the maximum supporting axial force appears in the second of the three supports,and the first support is the second However,the third channel has the smallest support;the bottom of the foundation pit has a large bulge after the excavation of the three layers of soil,the middle bulge value is large,and the wall side bulge value is small,and it is distributed in a dumbbell shape.(2)The simulation results of the construction plan under the preliminary design show that the horizontal displacement of the ground wall,the supporting axial force,and the position of the base bulge exceed the monitoring control value requirements,and the stability has hidden safety hazards.(3)Use the single factor analysis method to optimize the preliminary design,compare the three support schemes of one concrete support + two steel supports,two concrete supports+ one steel support,and three concrete supports,and comprehensively consider the optimization effect and monitoring control requirements And the construction period cost requirements,decided to adopt the support plan of two concrete supports + one steel support;compare the 3m,4m,5m basement stirring pile three kinds of foundation reinforcement plans,comprehensively consider the optimization effect,monitoring control requirements and construction period cost requirements to decide to adopt the 4m basement The mixing pile strengthens the base.(4)Stability calculations were carried out for the optimized design scheme and compared with the on-site monitoring results.The results showed that the maximum horizontal displacement value of the wall was reduced from the preliminary design 20.52 mm to 11.84 mm,and the wall displacement was reduced.42.3%,the deformation is effectively controlled;the maximum support axial force is reduced from 862 KN in the preliminary design to 424.33 KN.Compared with the original support plan,the support axial force is reduced by50.7% after optimizing the support measures;the base uplift value is reduced from27.58 in the preliminary plan.mm dropped to 15.82 mm,a decrease of 42.6%.The monitoring results of the supporting structure are consistent with the numerical analysis results of the optimized design.The monitoring results are slightly larger than the numerical analysis results,but they all meet the monitoring control value requirements.The optimized design parameters of the deep foundation pit supporting structure of Licun Station of Foshan Metro Line 3 are reasonable.The research results are reliable. |
