Clogging Mechanism Of Drainage Holes And Development And Application Of New Fiber Bundle Drainage Pipes

Subgrade drainage system is an important part of road structure,which is of great significance to reduce subgrade water loss disaster and improve road stability.At present,the serious blockage of rainwater drainage pipeline has become an engineering problem difficult to solve in subgrade engineering,which seriously endangers the quality and safety of subgrade engineering.Therefore,it is very necessary to carry out research on anti blocking of drainage pipeline,and consider "prevention first,prevention combined",so as to fully solve the problem of drainage pipeline blocking.Based on indoor test,theoretical analysis and numerical simulation,this thesis studies the anti blocking technology of drainage pipe,develops a new type of fiber bundle drainage pipe,and optimizes its design parameters,so as to realize the anti blocking of subgrade drainage pipe.The main research contents and achievements of this thesis include:(1)Based on the discrete element method,the drainage calculation model of ordinary subgrade drainage hole is established to simulate the drainage process of subgrade,and the mechanism of drainage clogging of ordinary drainage hole is revealed.The results show that when the soil particles enter into the pores under the action of water flow,the integrity of the skeleton structure of the indirect contact force of the soil particles is damaged,and the movement of the soil particles mainly diffuses to the place where the difference between the hydraulic gradient and the contact force of the soil particles is large.When the upper particles rely on their own adhesive strength and the micro soil arch to resist the impact of water,the arch shape can reach a new equilibrium state,and the side opening is more difficult The results show that the shape of soil particles is similar to half heart,and the diffusion direction of soil particles is inclined to the upward position with lower earth pressure.(2)Carry out indoor test,develop a new type of fiber bundle drainage pipe,and study the drainage performance of the new type of drainage pipe,determine the material composition and structural form of the new type of fiber bundle drainage pipe.The results show that the drainage effect of drainage pipe decreases in turn according to the fiber bundle materials:plastic,hemp,polyester,cotton and nylon;different fiber bundle arrangements in drainage pipe have different seepage effect;the more fiber bundles are arranged,the more significant the seepage effect is.It is suggested to arrange 20 fiber bundles in 100 mm diameter drainage pipe;the higher the fiber bundle density in unit range,the better the drainage effect is The higher the sand content in the soil,the better the drainage effect.(3)Based on the theoretical calculation and numerical simulation method,the influencing factors of the design of the new fiber bundle drainage pipe are studied,and the optimal design parameters of the new fiber bundle drainage pipe are proposed.The results show that in order to drain the water from the subgrade in time,drainage pipes should be set up in the water rich section;multiple drainage pipes should be set up or drainage pipes should be set up on the upper part of the subgrade to drain the subgrade water quickly;in the design,the method of conservative design row spacing can be adopted to properly form a joint drainage area;in engineering practice,the design inclination of drainage pipes should be controlled to 3 degrees,In order to achieve the highest drainage efficiency,the longer the length of the drainage pipe,the greater the displacement,and the length of the lower drainage pipe has greater influence on the drainage effect than the upper drainage pipe.(4)Combined with the expressway project under construction,the application test of the new fiber bundle drainage pipe project is carried out,and the construction technology of the new drainage pipe is proposed to improve the construction quality.The results show that through strict control of the construction process,the construction is carried out according to the construction process mentioned in this thesis,including filling the pit with good water permeability,using hard gravel as the filter layer,spreading fine sand on the gravel as the transition layer,using high-speed hydraulic rammer to backfill and compact the filling layer by layer and other measures to ensure the best drainage effect of the new fiber bundle.