Study On The Key Technology Of Continuous Casting Of Concrete Well Walls Using Sliding Formwork Under Mud

With the increasing depth of solid mineral resources exploitation,the strata traversed by vertical wellbores are evolving increasingly complicated and bringing more difficulties to construct.The well drilling method has converted to the main research interest for intelligent excavation of deep wellbores due to its construction characteristics of “drilling without digging” and the advantages of applicable to various complicated geological and hydrogeological conditions.As the depth and diameter of the wellbore increase,the construction of the drilling wall is restricted by the technical bottleneck of being unable to float or sink because of the definite heavy wall,hence it is of urgent need to develop exceeding technology of drilling wall construction.To this end,the technology of pouring drilling walls using sliding formwork below slurry was researched and developed by China University of Mining and Technology.In this thesis,the feasibility and several difficulties of this technology are investigated using specimen tests,physical model tests and numerical simulation methods,and the main results are as follows.Firstly,the effect of temperature and UWB-Ⅲ flocculant content on the condensed time of underwater anti-washout C80 concrete was obtained.The effect of temperature on the condensed time of concrete is very significant,and the initial and final condensed time of concrete reduced sharply with the increase of curing temperature,the time difference between the initial and final condensed time is also getting shorter.With the increase of flocculant content,the condensed time first decreases and then increases.The optimum demold time was obtained by small model tests.Secondly,a laboratory bench was designed and manufactured to meet the requirements for continuous pouring of the well wall underwater according to similarity theory,and five model tests were carried out and several improvements were made to the laboratory bench corresponding to the problems within tests,to realize the function of pouring high-strength concrete well wall below slurry continuously.The results of the appearance and strength tests showed that the well wall was of excellent quality,thus confirming the feasibility of using a slipform pour-in-place drilling wall process below slurry.The experimental study concluded that the addition of a water separator and extension formwork to the main sliding formwork could effectively solve the problem of concrete condensation above the mouth of the pouring conduit during the continuous pouring of the well wall below slurry in the long-term.The injection of water under the bottom sealing formwork through a one-way valve could make the demold of the side formwork successfully and the overall formwork sliding up smoother.Finally,research on numerical calculations of the temperature field and temperature stress field of the newly constructed concrete well wall under different working conditions were carried out.The results show that as the pouring height of the well wall exceeds 13 m,the effect of pouring height on the temperature field of the well wall was basically none,and the height of 13 m could be considered as the critical height of the pouring well wall.The temperature of the concrete into the mold and the ground temperature environment had a greater influence on the temperature field.The pouring well wall using this technique generally did not produce temperature cracks,and the water sealing properties of the wall could be guaranteed.The feasibility of the pour-in-place drilling wall below slurry is verified from the perspective of numerical simulation.The above-mentioned research results prove that it is feasible to use sliding formwork below slurry to pour the drilling wall continuously as a whole.This technology has overturned the traditional construction technology of “prefabricated on the ground,floating and sinking in the slurry” for drilling walls,and the research results play an important role in promoting automatic and intelligent construction of deep vertical wellbores.This thesis has included 193 images,19 tables and 132 references.