Mechanical Law Of Single-layer Inclined Shaft Lining Constructed By Freezing Method In Aqueous Porous Stable Strata

In view of the lack of scientific basis for the design of single-layer inclined shaft lining constructed by artificial ground freezing in water-bearing porous stable strata,the stress and deformation laws of that shaft lining considering the whole freezing sinking process was studied by combination of theoretical analysis,numerical calculation and physical simulation test.Based on this,the design theory and method of circular section shaft lining were established,and the guidelines of noncircular section shaft lining design were proposed.Firstly,the mechanical quality of single-layer inclined shaft lining during sinking by freezing method in aqueous porous rock layer was analyzed.The initial ground stress was decomposed according to static equilibrium into equivalent skeleton pressure and equivalent pore water pressure,and the plane strain analytical solutions of interaction model of shaft lining,frozen wall and rock layer with the whole process of freezing sinking were built separately under those two initial pressures.In view of the pore expanded by water pressure,the effect of pore water pressure that reapplied in surrounding rock after frozen zone thawing on the shaft lining stress was obtained.The analytical solutions of the stresses and displacements of shaft lining,frozen wall and aqueous stratum under all four construction steps of freezing,excavating,building and thawing were derived for the first time.The mechanism of shaft lining and surrounding rock separated by pore water pressure was revealed.The influence of various factors in every construction stage on the stress and deformation of circular-section inclined shaft lining was comprehensively analyzed,and the factors priorities were distinguished.Also,this is the first design theory and method for circular inclined shaft lining with the consideration of pore water pressure.The research shows that pore water pressure and porosity are the primary factors affecting the shaft lining stress,and the function enhances with two main factors.The total load on shaft wall should be the sum of equivalent skeleton pressure and equivalent pore water pressure which are calculated by stratum structure method respectively.The maximum load of shaft lining is when frozen wall thaws completely,and it should be the load value in the design calculation.Secondly,regarding the characteristic of water-bearing porous stable strata and the whole process of freezing sinking,two large-scale plane strain numerical models of interaction of inclined shaft lining,frozen wall and aqueous porous rock mass were first established considering initial skeleton pressure field and random pore water pressure field.One for the circular section,another for the section of vertical sidewall,semicircular top arch and inverted arch.A method of simulating three-dimensional stress of shaft lining in porous aquifer was put forward through averaging calculation results of multiple random pore models.With the consideration of pore water pressure,the stress and deformation laws of two kinds of sections shaft linings were revealed during all steps of freezing sinking,the influence of main factors on the stress and deformation of shaft lining is grasped,and the design guidelines of freezing inclined shaft lining with arches were obtained.The research illustrates that,for the circular section shaft,the normal load on the shaft wall outer edge calculated by the stratum-structure model with pore water pressure is 1.45-1.61 times as much as that without considering pore water pressure and is 0.26~0.52 times as much as the initial normal stress.Normally,there is no tension stress on the inner edge of circular shaft lining,and the control points of maximum and minimum compressive stress are at 0 and 90 degrees,respectively.For the shaft of vertical sidewall,semicircular top arch and inverted arch,tensile stress is not generated at the top arch and vertical wall,and the max-min control points of compressive stress are the center point of top arch and the intersection point of top arch and sidewall,respectively.The tension and compression control points of the inverted arch can be the center points of the inner edge and the outer edge.Thirdly,in the physical simulation test,a sealing method of noncircular section model shaft lining and test cylinder end cover for high pore water pressure was proposed.A set of shaft freezing technologies which can form preset thickness and average temperature of frozen wall was designed.A cylinder model test system was built which can simulate the stress law of noncircular section model shaft lining under high ground pressure and high pore water pressure during thawing process.Using the model test system,hydrostatic pressure experiment,combined loading of ground pressure and pore water pressure,and freezing and thawing test of co-loading of ground pressure and pore water pressure were carried out,and the deformation law of shaft lining under the above conditions was obtained.The test results show that the stress value of shaft wall is significantly lower than the initial ground pressure and pore water pressure under the interaction of shaft lining and surrounding rock.When pore water pressure becomes greater,the stress value of shaft lining increases,the same with the deformation difference of shaft wall between top arch and inverted arch.In the design of shaft lining in water-bearing porous stable strata,the equivalent water pressure and the equivalent skeleton pressure should be separately calculated to reflect the effect difference of them on shaft lining.The research results in this thesis provide a basis for more effective,reliable and economical design of inclined shaft lining in aqueous porous stable strata.In this dissertation,there are 192 figures,30 tables and 130 references.