表土段冻结壁解冻过程中斜井井壁受力规律研究

发布时间：2019-01-21 19:58

【摘要】：冻结法凿井工程中,斜井井壁在冻结壁解冻过程中的受力情况,历来是斜井建设工程的一个研究盲点。而伴随着冻结壁解冻,斜井井壁受温度场、水分场、力场等多场作用,受力工况复杂。开展此阶段研究工作,对斜井井壁设计、施工大有裨益。基于此,本文采用数值模拟与模型试验相结合的方法,对表土段冻结壁解冻过程中斜井井壁的受力规律进行了研究。在数值模拟计算中,首先结合试验装置建立了平面有限元模型,对液压囊加载系统的可靠性进行了验证计算。并在此基础上,对可能影响加载系统的相关参数进行了单因素分析。最后,利用顺序耦合的方法,对温度场、应力场进行耦合作用分析,得到了斜井井壁在冻结壁解冻过程中的受力规律。研究表明,采用液压囊、水压共同加载以达到封闭空间内三轴加载效果的试验方案是可行的。加载过程中,加压钢板厚度与土体水平侧压力系数取值对加载效果的影响比较大。冻结壁在解冻过程中,井壁内、外缘关键点的受力基本上都呈现逐渐增大的趋势。其中,井壁顶拱内缘中心受到的拉应力最大,仰拱内缘中心发生的径向位移最大,此两点受力在井壁各关键点中处于最不利状态。在井壁结构设计、施工过程中,应予以着重考虑。在模型试验中,首先通过数值计算,确定了钢质模型井壁的尺寸。并利用该模型井壁进行了静水压加载试验、纯地压加载试验、地压与孔隙水压联合作用试验以及冻结壁解冻过程中的井壁受力模拟试验。研究发现,静水压力试验中,模型井壁两端有无圆形钢头对试验中井壁的受力影响微乎其微,实测出的井壁环向应变与数值模拟计算的结果基本上完全吻合。纯地压加载试验中,仰拱内缘中心的环向应变与顶拱内缘中心的环向应变均随着Y方向荷载Yp的增加而线性增大;Yp大小一定时,X方向荷载Xp越大,仰拱内缘中心和顶拱内缘中心的环向应变越小。地压与孔隙水压联合作用试验中,仰拱内缘中心的环向应变随着孔隙水压的增加而增大,顶拱内缘中心的环向应变随着孔隙水压的增加而减小。冻结壁解冻阶段加载试验中,模型井壁中的温度应力抑制了顶拱内缘中心与仰拱内缘中心在冻结壁解冻过程中受到的孔隙水压拉应力作用,顶拱与仰拱中心环向应变随着冻结壁温度的上升而逐渐减小,这与数值模拟计算得到的结果不相一致。最后,给出了通过开展数值模拟与模型试验研究得到的主要结论,并针对研究过程中出现的不足提出了改善性建议。
[Abstract]:The stress of inclined shaft wall during thawing process is always a blind spot of inclined shaft construction project. With the freezing wall thawing, the inclined shaft wall is subjected to many fields, such as temperature field, moisture field, force field and so on. The research work at this stage is of great benefit to the design and construction of inclined shaft lining. Based on this, the method of numerical simulation and model test is used to study the force law of inclined shaft wall during thawing process of frozen wall in surface soil section. In the numerical simulation, the plane finite element model is established in combination with the test device, and the reliability of the hydraulic bag loading system is verified and calculated. On the basis of this, the single factor analysis of the related parameters that may affect the loading system is carried out. Finally, by using the method of sequential coupling, the coupling effect of temperature field and stress field is analyzed, and the force law of inclined shaft wall during the thawing process of freezing wall is obtained. The results show that it is feasible to apply hydraulic bag and hydraulic pressure together to achieve the effect of triaxial loading in closed space. During loading, the thickness of compression plate and the lateral pressure coefficient of soil have great influence on the loading effect. During the thawing process of freezing wall, the stress on the key points of the outside edge of the shaft wall is gradually increasing. Among them, the tension stress at the inner edge of the top arch is the largest and the radial displacement at the inner edge of the inverted arch is the largest. These two forces are in the most disadvantageous state at the key points of the shaft lining. In the design and construction of shaft lining structure, we should pay more attention to it. In the model test, the dimension of the steel model shaft wall is determined by numerical calculation. The hydrostatic loading test, the pure ground pressure loading test, the combined action of ground pressure and pore water pressure and the simulation test of wall force during the thawing process of freezing wall were carried out by using the model. It is found that in the hydrostatic pressure test, the influence of the circular steel head at both ends of the model shaft wall on the stress on the shaft wall is minimal, and the measured circumferential strain of the shaft wall is in good agreement with the numerical simulation results. The circumferential strain of the center of the inner edge of the inverted arch and the circumferential strain of the center of the inner edge of the top arch increase linearly with the increase of Y-direction load Yp. The larger the Xp is, the smaller the circumferential strain of the center of the inner edge of the inverted arch and the center of the inner edge of the top arch is. The circumferential strain of the inner edge of the inverted arch increases with the increase of the pore water pressure, and the circumferential strain of the inner edge of the top arch decreases with the increase of the pore water pressure in the combined test of ground pressure and pore water pressure. In the loading test of freezing wall during thawing stage, the temperature stress in the model shaft wall inhibits the pore water pressure and tensile stress in the center of the inner edge of the top arch and the center of the inner edge of the inverted arch during the thawing process of the frozen wall. The central circumferential strain of the top arch and the inverted arch gradually decreases with the increase of the freezing wall temperature, which is inconsistent with the results obtained by the numerical simulation. Finally, the main conclusions obtained by numerical simulation and model test are given, and suggestions for improvement are put forward in view of the deficiencies in the research process.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD262

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