| With the transformation and upgrading of infrastructure construction mode and the advancement of municipal engineering construction technology,the non-excavation underground pipeline laying technology has made great progress,and has been listed as an important branch with broad development prospects by the international construction industry.Because the non-excavation technology has the advantages of not disturbing traffic,not destroying the green space vegetation,and not affecting the normal life and work order of the surrounding people,it is widely used in various construction projects that are not allowed or cannot be excavated.Horizontal direction drilling(HDD)has been widely used in the construction of long-distance pipelines crossing rivers and roads due to its high construction efficiency,low cost and low environmental disturbance.The core technology of horizontal directional drilling through construction is the reaming and the last pipe back towing construction,so it occupies an important position throughout the construction process.A variety of national or industry specifications also give a variety of calculation models for directional drilling and dragging force,but there are various construction conditions in the actual construction process,and there are many factors affecting the dragging force.Based on the actual project of the city's Houzhai water plant,this paper studies the optimal calculation formulas and parameters suitable for the directional drilling back-draw force in Zhengzhou area as follows:(1)By studying the theory of the existing drag-forward calculation theory,the differences between the characteristics of each formula and the comparison are summarized.Combined with the actual project Houzhai Water Plant wearing the South-North Water Transfer,this paper proposes the formula recommended by GB50423-2013 Code for Design of Oil and Gas Pipeline Crossing Engineering,GB50268-2008 Water Supply and Drainage Pipeline Engineering Construction and Acceptance Specification recommendation formula,unloading arch soil pressure,net buoyancy was compared.(2)The directional drilling back drag force is mainly composed of the frictional resistance between the pipe soil,the drag resistance of the drag of the mud dragging mud,and the winch effect.For the western part of Zhengzhou,which is mainly dominated by siltous soil layers,each factor needs to be selected in conjunction with the actual project.The research suggestion in this paper is that the returning force formula of the steel pipe andplastic pipe given in the Technical Engineering Regulations of Horizontal Directional Drilling Pipeline Engineering of China Engineering Construction Association(CECS382-2014)should be adopted.The coefficient of friction between the soil and the soil should be between 0.3 and0.4(the range specified in the regulation is 0.1 to 0.3).For the viscosity coefficient of the mud,this paper recommends using the falling ball method or using the NZ-3A viscosity coefficient viscosity meter if the conditions are met,(3)On the basis of the above research,the DN1200 water pipeline of Houzhai Water Plant of Zhengzhou City,is designed to be crossed by the main channel of the Middle Line of the South-North Water Transfer.When the friction coefficient of steel pipe and soil is 0.55,the calculated drag force is 453.8t,which is close to the final measured value of 433.9t,which verifies the applicability of the model.In this paper,several calculation models for directional drilling back-draw are compared and analyzed,and the optimal formula and main parameters are proposed in combination with the soil properties in Zhengzhou area,which has certain reference significance for the subsequent engineering design and construction in Zhengzhou area. |
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