Avtomobilʹnyj Transport (Harʹkov) (Nov 2018)
Managing the process of correction of the working body movement trajectory at the static soil puncture
Abstract
Abstract. One of the most effective methods for the formation of horizontal wells for trenchless laying of underground utilities is the puncture of the soil with a cone-cylindrical tip. One of the major drawbacks of the method is the high probability of its deviation from the project trajectory. The reason for this may be different soil density in height, stony inclusions, not accurate positioning of the working body in the initial stage of the process. This disadvantage significantly reduces the scope of application of the puncture method at short distances within 15 ... 20 m. It is possible to increase this distance by promptly correcting the trajectory of the working body in the ground. The paper reveals the possibility of controlling the trajectory of the working body movement by adapting the shape of its tip, and determines the conditions for motion correction when the soil puncture process is continuous. The originality of the solution includes the following. In case of deviation of the working body movement from a given trajectory, the traditional conical shape of the tip is replaced by an asymmetrical one, which is acted upon by the transverse force from the soil reaction. This force in turn leads to a change in the direction of the working body movement towards the displacement of the asymmetric tip. Previously it was found that the deviation of the working body is influenced by both the angle of inclination of the frontal surface of the tip and the properties of the soil. Given these circumstances, you can control the trajectory of the well in the process of its formation. It has been established that the trajectory of the soil puncture will be the most effective in the case of its tendency to the minimum length of the correction area. In its turn, the curvature of the axis of the borehole should not be less than the allowable values of bending stresses in the pipes that occur when they are pulled through curvilinear sections. A method for calculating the effective puncture trajectory, which is based on determining the allowable stresses in pipelines during their bending, is proposed. The bending line of the pipeline was taken as part of a circle. The results of the calculation according to the obtained method showed that, for example, when a steel pipeline with a diameter of 159 mm with a wall thickness of 6 mm deviates, the theoretical length of the section for correcting the movement path of the working body from the maximum deflection point of 1.66 m to the point of contact with the project path should be 23 m. Experimental studies have proven that the length of the section for this case was 27 m. The discrepancy between the experimental data and theoretical values does not exceed 15 %, which can be considered as the basis for practical use in controlling the process of the soil puncture path. The obtained recommendations for the management of the puncture allow expanding the area of effective application for a distance of up to 100 m. In this case, the correction of the movement of the working body in the soil can be up to 4-5 times.
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