| As the further improvement of urbanization level has been promoted by the rapid development of economic and social level,some of the drainage pipes currently in operation cannot effectively meet the needs of urban functions.Trenchless technology is gradually replacing the excavation method due to the advantages of lower comprehensive cost,higher safety and short construction period,and is widely used in pipeline laying and repair and renovation projects.The current research and development direction of trenchless pipe laying technology is the combination of multiple construction processes.Combining the advantages of HDD and mcrotunneling technology,directional mcrotunneling is a construction method that is Suitable for small and medium pipes’ installation,which is where the industry’s development trend lies.This passage combined with actual engineering to conduct systematic research about directional mcrotunneling method.The main results are as follows:(1)Based on the actual project,the construction method of directional mcrotunneling is summarized,and the design method of specific parameters is described,which provides a basis for the selection of pipe materials,the selection of machinery,and the design of construction schemes.(2)Based on the research on the calculation model of the pipe laying force of the existing trenchless pipe installation methods,the physical model of the pipe installing process is established in combination with the actual project and the theoretical calculation formula of drag force is proposed.The four parts of front resistance of cutter,lateral resistance of pipe,lateral resistance of drill pipe and cutter torque are calculated separately,and the calculation model has been programmed.(3)The finite element method was used to study the joints of HDPE wound solid wall pipe commonly used in the directional mcrotunneling process.The self-tightening seal of the seal ring under full compression can resist 3.13 MPa pressure,but the gap between the joints will cause the sealing performance to decline significantly,and the seal will fail when the gap is 2mm.The tensile load of the joint is mainly borne by the two sealing teeth at the proximal end.The maximum stress occurs between the two sealing teeth.When the load reaches 150 k N,local yield begins to occur.The coupling shear stress is concentrated in the squeeze area and linearly distributed along the seal teeth.Under excessive deviation,the seal teeth of the coupling will separate,resulting in seal failure.The optimal design of the sealing performance of the coupling and the sealing tooth structure was studied.The contact stress of the sealing ring increased with the decrease of the depth of the limit groove,and the depth of the limit groove after the optimized design was 4mm.The stress distribution of couplings with different number of sealing teeth is similar,and the stress at the coupling decreases as the number of sealing teeth increases.(4)Taking the DN600 drainage pipeline installation project in Panyu District,Guangzhou as an example,the design and construction method of the directional microtunneling process engineering project is explained in detail,and the rationality of the calculation formula is verified.The front resistance and lateral resistance as the main components account for up to 55% and 40.6%,and the weight of the load increment caused by mud drag resistance and drill pipe direction change is relatively small,respectively 1.8% and 1.5 %.The drag force changes dynamically with various engineering parameters and installing distance.Among them,the shape of the pipeline trajectory,the friction coefficient and the expansion plan have a significant effect on jacking force,while the mud parameters and installing rate have little effect. |
PDF Full Text Request