Study On The Inhomogeneity Of Horizontal Lateral Pressure On Shaft Lining

Using the current shaft design specification to compute the radial horizontal exterior loads of freezing-sinking in the deep earth circumstances, a great thicker shaft lining would be in demand if the non-uniform parts of the horizontal exterior loads on shaft were checked out. Actually lots of the shafts did not have the checking calculation of the nonuniform horizontal loads, yet the fracture because of the inhomogeneity of pressure have not emerged. The thickness of shaft lining is such a important parameter for shaft design and construction,and it relates to construction and operation of shaft and the safety of whole mine. Viewed from domestic and foreign research, whether the existing distribution form agrees with the facts and the uniformity coefficient are valued reasonably that is the problem to be solved. In this paper, a deeply and systematic study is carried out toward those problems.Firstly, theoretical analytical analysis method is given to study the distribution form of horizontal lateral pressure on shaft lining under variable initial earth pressure in two directions. After induction, nonuniform lateral pressure can be expressed as a formula p=p0(1+βcos2θ). Then a numerical simulation method is adopted to verify those problems. The further discussion demonstrates that nonuniform lateral pressure also can be described by p=p0(1+βcos2θ) even if there is a certain range of plastic zone in stratum. The existence of plastic zone makes the fitting of this formula decreased. The obtained pressure distribution in general accord with the elastic theoretical analysis results.Started with two kinds of uncertainty factors: physical parameters and geometric size, the stochastic finite element method is used to discuss the each factor which may affect the lateral pressure distribution of shaft. All the factors are as follows: shapes of shaft inner and outer edge; physical properties of the shaft materials; the physical properties of the frozen wall; physical properties of the stratum; tilted strata; deflective distribution of freezing hole. By means of a lot of random sampling, the degree of various factor's influence on nonuniform coefficient values of horizontal lateral pressure from the statistical regularity is obtained, the proportion between maximum and minimum pressure values is obtained, to provide the basis for determining the nonuniform level of lateral earth pressure, and lay the groundwork for the value ofβ, namely non-uniform coefficient which is a crucial parameter in the formula p=p0(1+βcos2θ).Physical tests are carried out to deliberate the stress state of the shaft when the stratum material is single and the shaft is drilled through a tilted stratum. When sand is chosen as the single material, the proportion between horizontal pressure on the shaft imposed by sand and vertical stress is 0.35. The sand layer is set to different angles, and for each angle, the lateral pressure distribution on shaft and the value of non-uniform coefficient is acquired.Later, the problem for nonuniform earth pressure is decomposed into three subproblems. Based on previous study, the conclusions was summarized and integrated, and all the relevant conclusions came down to this three subproblems. The distribution of nonuniform earth pressure, the determination means for maximum or minimum values, and the value of coefficientβwere compared, analysised and verified deeply.Finally, After summarizing, the proposal is: the formula p=p0(1+βcos2θ) is choose as reasonable form to calculate the nonuniform horizontal earth pressure on shaft lining in thick topsoil. p0 stands for permanent soil-water pressure.For outer freezing-shaft,β=0.05; for the thawed-shaft,β=0.15.There is 92 charts, 63 tables, 83 references in this paper.