Research On Application Of Compound Dewatering Technique Of Vacuum Tube Well

With rapid development of city construction, subway traffic was also growing rapidly. It is difficult to handle underground water in the process of subway construction. There is a difficult problem in the process of Beijing subway construction as to dewatering perched water, aquitard, water in saturated soil and relict water in aquifer interface by using conventional precipitation method, and the construction has to be worked with water, which bring a hidden trouble to the tunnel excavation with the rapid economic way and a safe and civilized construction, it is a problem to be solved urgently in the subway construction. The new method of compound dewatering technique of vacuum tube well, the integration of vacuum technology and tube-well technology, is proposed in this thesis for solving the precipitation problem during construction. Indoor physical simulation test, field engineering test, field experimental study, the study of basic theory and engineering design have been conducted. The research results are of great significance in theory and engineering applications. The research work done is presented as follows:Compound dewatering technique of vacuum tube well is an effective technology for solving the dewatering problems of aquitard and interface relict water according to physical simulation test and field test. The variation laws, such as degree of vacuum, pore water pressure in different strata, have been studied. The results show that there is a certain scope of influence of vacuum in strata, and the vacuum degree in the horizontal direction decreases gradually with the increase of the distance from the main well; the change law of degree of vacuum in the vertical direction increases firstly and then decreases with the depth of soil strata, and changes with different soil nature and depth; changes of pore water pressure in soil strata has also shown a similar law of degree of vacuum.Based on the results of laboratory physical simulation test and field test, distribution characteristics of seepage field and vacuum field caused by compound dewatering technique of vacuum tube well have been analyzed, the effective influence radius of vacuum field are related to the degree of the vacuum in well, characteristics and buried depth of strata and so on. The greater the degree of the vacuum in well cause, the greater the effective influence radius of vacuum field are. Under the same conditions, the more deep the same stratum buried, the greater the effective influence radius of vacuum field are. Numerical analysis has been conducted to verify the test data gained in inter-zone of An Ding road and Bei Tucheng, and the variation similar to field measurement is presented.Key design parameters, such as well depth, influence radius of vacuum, influence radius of pumping and single-well outflow have been analyzed on the theoretical research, the corresponding calculation method and empirical formula are given, which provide technical support for the extension and application of compound dewatering technique of vacuum tube well technology to provide technical support; the main structural parameters and sealing measures of vacuum tube well are raised according to field tests. Environmentally friendly material and automatic control system are developed.