【作者】 杨志江；

【导师】 杨维好；

【作者基本信息】 中国矿业大学 ， 岩土工程， 2019， 博士

【摘要】 针对400～800m深厚土层冻结壁设计问题,本文综合采用解析分析、数值模拟和工程实测方法,研究了“开挖卸荷”和“与地层共同作用”实际工况条件下冻结壁的受力和变形规律,构建了冻结壁弹塑性设计新方法,通过实际工程验证了新理论的适用性和可靠性。首先,分析了凿井过程中冻结壁的实际工况特点,建立了“开挖卸荷”和“与地层共同作用”工况下冻结壁的平面应变力学模型;推导了冻结壁和地层应力和变形的解析解,获得了冻结壁临界地压和变形的表达式,揭示了地层对冻结壁受力和变形的影响规律,比较了共同作用模型与传统模型的差异。结果表明:受地层抗剪能力影响,冻结壁受力和变形小于传统模型;仅当地层完全不抗剪(剪切模量或强度参数趋于0)时,冻结壁外边界压力和承载能力与传统模型一致,但变形仍小于传统模型;在常见力学参数下,地层多处于弹性状态。因此,深厚土层冻结壁设计应考虑冻结壁和地层的共同作用,以充分利用地层承载能力。其次,考虑冻结壁与地层共同作用编制了凿井施工过程有限元模拟程序,分析了800m深厚土层冻结壁应力和变形场特征及其随施工过程的演变;获得了井筒内部地层冻结状态、施工段高、冻结壁几何参数和冻土力学参数对冻结壁应力和变形的影响规律;分析了平面应变模型解析解与凿井施工模型数值解的差异。结果表明,有限施工段高减小了施工扰动影响范围,使冻结壁外边界接近初始应力状态,进而使外侧地层易于保持弹性状态(所有计算组地层均为弹性);平面应变模型解析解总体反映了冻结壁应力和变形的分布和演变特征,其井帮位移和塑性区范围大于凿井施工模型数值解,按平面应变模型进行冻结壁设计具有较高的安全储备,且可通过减小施工段高和改善井内地层冻结状态有效提高安全储备。再次,基于冻结壁变形规律解析分析和数值计算研究成果,推导了冻结壁厚度设计公式,给出了设计参数的取值方法,构建了冻结壁弹塑性设计新方法;获得了冻结壁设计厚度的影响因素及其影响规律,揭示了新方法与传统方法的异同。结果表明,传统弹塑性设计方法为新方法的特例,新方法利用了地层承载能力,设计的冻结壁厚度小于传统方法(算例表明比传统方法小15%～40%)。最后,采用新方法计算了土层厚度分别为675.6m和753.95m的龙固煤矿北风井(土层厚度首超600m)和万福煤矿风井(土层厚度首超700m)的冻结壁厚度,实测了冻结壁井帮位移、对井壁的变形压力、井壁混凝土应变和钢筋轴力,揭示了600m～800m深厚土层冻结壁变形规律。实测成果和工程总体效果表明,两井筒冻结壁具有足够的稳定性,按新方法设计冻结壁安全可靠且经济合理。本文揭示了600m～800m深厚土层冻结壁变形规律,拓展了传统冻结壁弹塑性设计方法,获得了适用于400～800m深厚土层的冻结壁设计新方法。该论文有图117幅,表41个,参考文献107篇。更多还原

【Abstract】 Designing a proper icewall for shaft sinking in 400m~800m deep soil by artificial ground freezing method is a quite big problem.In order to solving this problem,in this thesis,the deformation behavior of icewall and the co-bearing of icewall and stratum have been studied by analysis and FEM based on the actual unloading case of the icewall due to excavation.And then,a new elasoplastic design theory is developed and applied to two new shaft sinking project,in which the reliability of the new theory has been verified.Firstly,a mechanic model has been made with plane strain assumption to modeling the co-bearing of icewall and stratum in unloading case,and the stress and displacement solutions of icewall and stratum have been achieved.According to the solutions,the effect of stratum on icewall has been analyzed,and the difference between the co-bearing and tradition model has also been discussed.The result shows that the load,stress and displacement of the icewall which is quite effected by the anti-shear ability of stratum is generally smaller than the corresponding one of the tradition model.Only when the shear modulus and strength parameters tend to zero,the load and bearing capacity of the icewall tend to,but the displacement is still less than,the one of the tradition model.So for icewall design in deep soil,the anti-shear ability of stratum should been made best of to enduce icewall thickness.Secondly,finite element models have been built to simulate shaft sinking and lining process.Based on the models,the characters of the stress and deformation field of icewall in 800 m deep soil and their evolution have been analized;the effect of sinking section,freezing status of the soil to be excavated and the icewall parameters on the load,stress and displacement of the icewall has been studied,and the difference between the analytic and the FEM solutions has also been discussed.Results indicate that the analytical solutions catch the distribution characters of stress and displacement of icewall,but the displacement value and the range of plastic zone of the analytical solutions is bigger than those of the FEM solutions.So it is safe and the safety could been enhanced by reducing sinking section and intensifying freezing the soil to be excavated when designing the icewall according to the plane strain model.Thirdly,icewall design formulas have been presented base on the analytical solutions of the plane strain model and it’s parameters are discussed.As results,the traditional design formula are special cases of those developed in this thesis.Because of the bearing capacity of stratum utilizing,icewall thickness designed by new formula is more less than the one by traditional ones,and examples show that the former is 15%~40% less than the latter.Finally,the new theory has been adopted to determine the icewall thickness of the ventilation shaft of Wanfu coal mine of which the soil depth is 753.95 m and the north ventilation shaft of Longgu coal mine of which the soil depth is 675.6m.During sinking and lining,the icewall displacemen,the freeze pressure,the rebar force and the concrete strain are all measured in both project.Results show that measured displacement values are smaller that the one required by construction code,curves of freeze pressure versus time are similar to those of adjacent shaft constructed,rebar forces are less than the yielding ones and strains are under the critical one.So the lining is safe and the icewall is stable,which indicates the new design theory is reliable and economical.This study extends the traditional elastic-plastic design theory of icewall to 400m~800m deep and has great value in application and academic.更多还原