Performance-based Research And Development Of New Technique Towards Deep Excavation Construction Of Car-parking Wellholes

With the continuous progress of urbanization in our country,the number of cars per capita is increasing.Parking facilities are difficult to meet the demand for parking space due to the growth of vehicles.Parking gaps are increasing,and the problem of "parking difficulty" is particularly prominent.This dissertation describes the concept and structure of wellhole underground garage,and develops a new construction technology system for excavation based on a series of performance analysis of construction process according to its engineering characteristics of ultradeep and small area excavation.The main research contents and results are as follows:(1)This paper analyzes and simulates an ultra-deep wellhole underground garage project in Hangzhou using soldier-pile retaining structure,especially studies the deformation characteristics and surface settlement of such structure in the during excavation construction,and obtains a suitable numerical analysis model and related parameters.(2)Based on the finite element model of soldier-pile support,the supported excavation was changed to the traditional caisson sinking construction,and it was found that the cantilevered caisson structure deformation was much larger than that of the soldier-pile support,with large bottom heave and poor stability against basal stability,indicating that the traditional caisson method is difficult to meet the requirements for structural deformation control when used in the construction of ultra-deep excavation.After further contrasting the control effects of three methods of increasing the wall thickness of caisson,sinking with partition wall and vertical mud-water balance method to control the deformation of caisson wall in ultra-deep wellhole excavation,it is found that by optimizing traditional caisson structure and its construction method,The wellhole deformation is well controlled and the structure is steadily increased.(3)Aiming at the problem that it is difficult to guarantee the stability against basal heave before bottom sealing,two kinds of construction control measures against upheaval are put forward and verified by finite element software,and the effectiveness of these two measures is proved.It can be combined with the future engineering application to further optimize the scheme.The new technology is applied to the traditional caisson method to solve the bottleneck problems of the traditional caisson in the aspects of supporting structure performance,construction technology and stability against basal heave.(4)The improved construction technology is integrated to form a new construction technology system for ultra-deep wellhole excavation supporting,which is applied to the design of excavation project of a wellhole garage in Wenzhou.The thickness of wellhole wall,the construction method of caisson and the stability against basal heave at the bottom of the excavation are optimized.Combined with the finite element software simulation results for further analysis,the results show that the structural deformation and excavation bottom basal heave resistance are well controlled,and it is safer and more convenient to cooperate with the vertical mud-water balance technology.