| Municipal water supply pipeline is closely related to People’s Daily life, but the frost damage and the increasing cost caused by too deep burial depth were existed in seasonal frost area. Based on existing theory and practical experience, the heat transfer, seepage mechanics and frost heave mechanics involved in the municipal water supply pipeline buried depth were studied. Combined with the corresponding experimental data, theoretical analysis and numerical simulation, the soil temperature field, water field and stress field around the water supply pipeline were analyzed systematically. The main results as follows:(1) Pipelines suffered from frost damage is mainly affected by the enlargement of soil volume during soil freezing process, which results the emergence of frozen force and frost force, and the change of soilco- mp action factor in the process of soil thawing. Among them, freezing force is related to the soil moisture content, temperature, base materials and other factors. Take the silt for instance, the freezing force is large-st when W=50%. Frost force include tangential frost force, normal frost force, anti- frost force.Through the study, frost force is related to water content of frozen soil, negative temperature, duration, foundation embedment depth(frozen depth) lithology(soil conditions) and other factors. Thawing settlement dama-ge is melt ing when the soil under the same external load, the bearing capacity of soil deformation of the fallsdue to the compressibility of the permafrost melts increase than the same kind of compressibility of soil.(2) Heat transfer between the pipe and the surrounding soil is mainly by means of heat conduction and convection. The finite element analysis method is mainly used in this research about heat transfer calculation problem. Make clear the basic steps and solving thinking of finite element method to solve the problem. The heat transfer involved in the steady heat transfer and unsteady heat transfer were analyzed by finite method. The heat transfer equation and the solving process were obtained for the two cases.Municipal water supply pipeline into the surrounding soil heat transfer belongs to the unsteady heat transfer problems(3) The main factors influence the municipal water supply pipeline buried depth in seasonal frozen soil area(Soil freezing depth, groundwater level, flow rate, pipe diameter).Taking municipal water pipeline laying completed for instance, invasion soil depth at 0℃, temperature drop along the pipeline and stationary cooling time were calculated in this paper.(4) The actual situation of heat transfer equation was established, which was used to analyze municipal water pipeline in a residential area of Kelamayi combined with finite element analysis software. Conclusion that: When buried depth is 0.3-1.3m, the surface temperature has a great impact on the soil temperature field, and the soil line 0℃ temperature rise gradually move toward the ground. When pipeline buried depth is 1.5-2.1m, 0℃ temperature line change has no longer obvious rule. As the pipeline buried depth increases, the degree of soil affected by the surface temperature decreases, and the temperature change is not obvious. At the same time, when the pipeline buried depth increases below 1.5m, the observed soil temperature has declined to a steady leveled from the figure. As the change of land surface temperature, the change of soil temperature no more greatly, so that pipeline buried depth of 1.5m is quite reasonable.(5) The soil water pipe stress changes with temperature change status is obtained in this paper. The stress change of the upper soil in horizontal direction and vertical direction and stress changes in different depth of soil. The distribution stresses of soil around pipeline are obtained by solving the stress and thus the status of the pipeline stresses are better analyzed. To avoid frost heaving damage to the pipeline, the stresses of different buried depth pipe are analyzed, and a reasonable depth pipeline is determined. |
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