双圈管冻结条件下饱水砂层中冻胀力变化规律研究
发布时间：2018-08-01 10:44
【摘要】：在冻结法凿井中,冻结管断裂事故时常发生,带来严重后果。据专家初步推测,砂层冻结壁内、外部的冻胀力是造成冻结管断裂的主要因素之一。为此,本文采用解析分析、物理试验和数值计算相结合的方法,对饱和砂层双圈管冻结过程中内部冻胀力的变化规律展开了研究。首先,根据厚壁圆筒理论,对双圈管冻结模型进行受力模型简化,首次提出采用厚壁圆筒拉梅解、位移连续、体积相容方法,对双圈管平面应变模型进行理论解析,建立冻胀力与冻结壁厚度的函数关系,得出冻胀力随冻结壁厚度呈先线性后加速的增长趋势。在理论解基础上,进行单因素分析,得出冻结壁弹性模量越大、冻结壁厚度越大、饱和介质含水率越大,冻胀力越大。其次,通过数值模拟研究,采用优化后的热应变系数计算方法,建立双圈管冻结空间轴对称模型,探究了典型参数下模型位移场、温度场和冻胀应力场的变化规律。得到冻结壁形成过程中,两圈管之间土体将发生径向、竖向位移,靠近内外圈中点处,位移量最大,内圈管和外圈管处位移值一致;另外,冻胀力改变模型内部应力分布,且竖向应力增幅大于径向应力。针对各因素的单因素分析得出,介质含水率越大,冻胀力越大,冻结管间距越大、排距越大,冻胀力越小。第三,自行设计模拟装置,通过试验研究获得了封闭环境下纯水、饱和砂冻结过程中温度场、冻胀应力场的变化规律。在试验筒约束下,模型内部产生较大冻胀力,冻胀力使得内部径向、竖向和切向应力明显增大,在试验研究范围内,冻胀力随冻结壁厚度呈线性增长变化。双圈管冻结条件下饱和砂层内部产生冻胀力,冻结管处于拉、弯应力状态下,若饱水砂层处因初始缺陷、接头等造成冻结管强度不足,极易造成断管事故,故冻结设计中,在穿越富水地层处,冻结管应采取错开接头、增加强度或异步冻结等措施,减小乃至避免冻胀力,从而有效避免断管事故的发生。
[Abstract]:In freezing shaft sinking, the breakage of freezing pipe often occurs, which brings serious consequences. According to experts' preliminary theory, the frost heaving force is one of the main factors causing the fracture of frozen pipe. In this paper, analytical analysis, physical test and numerical calculation are used to study the variation of internal frost heave force during the freezing process of double-circle pipe in saturated sand layer. Firstly, according to the thick-walled cylinder theory, the mechanical model of the double-ring tube freezing model is simplified, and the theoretical analysis of the double-ring tube plane strain model is proposed by using the Lamy solution of the thick-walled cylinder for the first time, the displacement is continuous and the volume compatible method is used to analyze the plane strain model of the double-ring tube. The relationship between frost heaving force and freezing wall thickness is established. It is concluded that the frost heave force increases linearly and then accelerates with the frozen wall thickness. On the basis of theoretical analysis, it is concluded that the greater the elastic modulus of the frozen wall, the greater the thickness of the frozen wall, the greater the moisture content of saturated medium and the greater the frost heave force. Secondly, through the numerical simulation study and the optimized calculation method of thermal strain coefficient, the axisymmetric model of double loop tube freezing space is established, and the variation law of displacement field, temperature field and frost heave stress field of the model under typical parameters are explored. The results show that during the formation of freezing wall, the soil between the two loops will have radial and vertical displacement, close to the middle point of the inner and outer ring, the displacement of the inner ring and the outer ring will be the same, in addition, the frost heave force will change the stress distribution in the model. The increase of vertical stress is larger than that of radial stress. According to the single factor analysis of each factor, the larger the moisture content of the medium, the greater the frost heave force, the greater the distance between freezing tubes, the larger the row distance and the smaller the frost heave force. Thirdly, the simulation device is designed, and the variation of temperature field and frost heave stress field in the freezing process of pure water and saturated sand in closed environment are obtained by experiments. Under the constraint of the test tube, there is a large frost heave force inside the model, and the internal radial, vertical and tangential stresses are obviously increased by the frost heave force. In the range of experimental study, the frost heave force increases linearly with the thickness of the frozen wall. Under the condition of double circle tube freezing, the frost heaving force is produced in saturated sand layer. When the frozen tube is in tension and bending stress, if the initial defect and joint of saturated sand layer cause the freezing pipe strength to be insufficient, it is easy to cause pipe breakage accident, so in freezing design, In order to reduce or even avoid frost heave force, the freezing pipe should take staggered joint, increase strength or asynchronous freezing in order to avoid the accident of pipe breakage.
【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】：TD265.3
[Abstract]:In freezing shaft sinking, the breakage of freezing pipe often occurs, which brings serious consequences. According to experts' preliminary theory, the frost heaving force is one of the main factors causing the fracture of frozen pipe. In this paper, analytical analysis, physical test and numerical calculation are used to study the variation of internal frost heave force during the freezing process of double-circle pipe in saturated sand layer. Firstly, according to the thick-walled cylinder theory, the mechanical model of the double-ring tube freezing model is simplified, and the theoretical analysis of the double-ring tube plane strain model is proposed by using the Lamy solution of the thick-walled cylinder for the first time, the displacement is continuous and the volume compatible method is used to analyze the plane strain model of the double-ring tube. The relationship between frost heaving force and freezing wall thickness is established. It is concluded that the frost heave force increases linearly and then accelerates with the frozen wall thickness. On the basis of theoretical analysis, it is concluded that the greater the elastic modulus of the frozen wall, the greater the thickness of the frozen wall, the greater the moisture content of saturated medium and the greater the frost heave force. Secondly, through the numerical simulation study and the optimized calculation method of thermal strain coefficient, the axisymmetric model of double loop tube freezing space is established, and the variation law of displacement field, temperature field and frost heave stress field of the model under typical parameters are explored. The results show that during the formation of freezing wall, the soil between the two loops will have radial and vertical displacement, close to the middle point of the inner and outer ring, the displacement of the inner ring and the outer ring will be the same, in addition, the frost heave force will change the stress distribution in the model. The increase of vertical stress is larger than that of radial stress. According to the single factor analysis of each factor, the larger the moisture content of the medium, the greater the frost heave force, the greater the distance between freezing tubes, the larger the row distance and the smaller the frost heave force. Thirdly, the simulation device is designed, and the variation of temperature field and frost heave stress field in the freezing process of pure water and saturated sand in closed environment are obtained by experiments. Under the constraint of the test tube, there is a large frost heave force inside the model, and the internal radial, vertical and tangential stresses are obviously increased by the frost heave force. In the range of experimental study, the frost heave force increases linearly with the thickness of the frozen wall. Under the condition of double circle tube freezing, the frost heaving force is produced in saturated sand layer. When the frozen tube is in tension and bending stress, if the initial defect and joint of saturated sand layer cause the freezing pipe strength to be insufficient, it is easy to cause pipe breakage accident, so in freezing design, In order to reduce or even avoid frost heave force, the freezing pipe should take staggered joint, increase strength or asynchronous freezing in order to avoid the accident of pipe breakage.
【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】：TD265.3
【参考文献】
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