Study On The Frost Heaving Force In Saturated Sand Under Condition Of Double Ring Of Freezing Pipes

Freezing pipe rupture frequently occurs in the process of artificial freezing mine shaft sinking, and it usually brings about serious consequences. According to experts’ initial speculation, frost heaving force inside and outside the frozen wall is one major contributor to the frozen pipes broken accidents. This thesis aims to carry out a research on the changing patterns of frost heaving force in the frozen process of double ring frozen pipes through analytical analysis, analog simulation test and numerical simulation.First of all, according to the theory of thick-wall cylinders, being aimed at the simplified mechanical model of double ring of freezing pipes,proposing for the first time displacement of thick wall cylinder lame solution and continuous, consistent volume method, on account of the in-plane strain model, setting up the function of the frost heaving force and the thickness of frozen wall, it is concluded that frost heaving force with the thickness of frozen wall after the first linear accelerated growth trend. Based on the theoretical solution, the factors affecting the single factor analysis, it is concluded that the greater the elastic modulus of frozen wall, the greater the thickness of frozen wall, saturated moisture content of medium, the greater the frost heaving force is larger.Secondly, through numerical simulation, using the optimized thermal strain coefficient calculation method, space axisymmetric model of double ring of freezing pipes is set up, exploring the typical parameters model of displacement field, temperature field and stress field change rules of the frost heave. During the forming process of frozen wall, radial and vertical displacement will occur between two circle tube, maximum displacement occurs at the midpoint, displacement about inner and outer ring pipes are consistent; In addition, the frost heaving force changes the stress distribution and the increase of vertical stress is greater than the radial stress. Aiming at the single factor analysis of various factors, the greater the moisture content of medium, the greater the frost heaving force; the bigger tube spacing and row spacing, the smaller the frost heaving force.Thirdly, through the designed simulator, through experimental study on the pure water in closed environment, in the process of freezing about saturated sand, the changing rule of the frost heaving stress field have been obtained. Constraints, frost heaving force is generated in a test tube of model, the frost heaving force makes the internal vertical and radial and tangential stress increasing obviously, within the scope of the test and research, frost heaving force linearly increase with the frozen wall thickness.Under the condition of double ring of freezing pipes, frost heaving force is generated in saturated sand layer, making the freezing pipes under tensile, bending stress, if the freezing pipes caused by the initial defects and joint strength is insufficient, easily to cause pipe accidents, so in the freezing design, through the rich water formation, staggered joint, freezing pipes should be taken to increase the strength or asynchronous freezing and other measures, reducing or even avoiding the frost heaving force, thus to prevent pipe accidents effectively.