Study On Construction Technology Of Earth Pressure Balance Shield In Watery Sand Stratum

In the field of tunnel engineering, earth pressure balance shield has been widely appliedbecause of its feature of stratum adaptability, safety, rapid construction speed, small influenceto the environment and the low engineering cost. With the development of city construction,the earth pressure balance shield is not only applied to good stability, low permeabilitystratum, such as rock and clay layer, but also gradually applied to watery sandy stratum withthe features of high permeability, high water pressure and poor competency. Earth pressurebalance shield tunneling in watery sandy stratum usually faces on a series of problems, suchas the difficulties of residue soil improvement, of EPB establishment, of soil output, spewingor mud cakes (mud cakes mainly occurring in the complex strata composited by sand andclay), which may lead to ground settlement. The difficulty of construction and the risk is veryhigh.In view of the problems of earth pressure balance shield in watery sandy stratum, basedon the research of former and scholar, From the adaptability of earth pressure balance shield，the structure and reformation of cutter and screw conveyor, and the measures forimprovement of residue soil，to the method of settlement control，the important constructiontechnology of earth pressure balance shield crossing sandy stratum is Systematicallysummarized and studied with engineering practice in this paper, which has value of shieldselection and reference in complicated geological conditions.①The geological characteristics of watery sandy stratum and the features of earthpressure were detailed analyzed in detail, and based on the engineering practice, the earthpressure balance shield parameters were calculated and its adaptability was analyzed.②Presents the concept of cutter side opening ratio. According to engineering practice,when the cutter side opening ratio was zero, the settlement of watery sandy layer is minimum.③By considering the earth pressure balance and the mechanical model of the earthpressure balance shield screw conveyor, the measure of screw conveyor reformation ispresented in order to improve the ability of the earth pressure balance shield to preventspewing.④Based on the exploration and summary of the project construction in different stages, a series of technology for settlement control, such as the earth pressure control, the selection ofcutter rotation speed, output control and residue soil improvement is presented.