Research On The Performance And Application Of The New Pavement Drain System

With the rapid development of economy and society in our country,the highway construction is entering a period of vigorous development.At the same time,the rapid development of highway construction,the water damage case of pavement structure and roadbed is increasing.Water infiltration into the pavement structure will make the base material in saturated state,reduce the load carrying capacity.The stability of pavement structure and the safety of the road may be threatened by the coupling of traffic load,so the urgent need to study on the fast and effective drainage of surface structure.The traditional pavement drainage is often used to set graded gravel below the base as drainage channels,which is often based on the "time-to-drain " drainage mode,when the base material is close to saturation to drainage.Due to the traditional design can not achieve the water drainage under unsaturated state drainage,the pavement is often in the saturated state,which affect the pavement structure carrying capacity.Based on unsaturated seepage theory,this paper proposes a new type of pavement structure,which is based on the use of geocomposite materials as drainage channels.The new drainage system of pavement structure is made up of three parts.From the top to the bottom part of the new drainage system is transport layer,capillary barrier layer,isolation layer.The new drainage system of pavement structure is designed to remove the water quickly and effectively in the structure of the pavement under the condition of unsaturated state,the damage of water on pavement structure is reduced.In this paper,the author uses unsaturated seepage theory to resesarch new drainage system of pavement structure drainage performance.Firstly,the indoor model test is carried out.Comparing with the new drainage system and the traditional drainage method,indoor model test measeurs the pavement structure layer drainage volume and matrix suction.Secondly,in order to solve the size limit and the single factor of consideration in the indoor model test,a numerical analysis model is further established for the consideration of unsaturated seepage flow.Compared with the model test results,the reasonable model parameters are determined.On this basis,the influence factors of the new drainage system are studied to provide the basis for the design of new drainage system.Finally,the new drainage system is applied to engineering practice.Model test results show that:1)The new drainage system in the first 8min after the rain began to drain,the suction value at this time is 40kPa.Using a new drainage system,the base in the unsaturated state will start drainage;2)The new drainage system is 1.25 times the amount of the traditional drainage,and can be more rapid drainage;3)The water storage in the base of traditional pavement structure is 3.6 times of the new drainage system.Numerical simulation analysis results show that:1)The variation law of suction in numerical simulation is basically consistent with the observed data.It is reasonable to explain the model construction and parameter selection in numerical simulation;2)When the new drainage system is used,the base suction began to decline after rainfall.At first 100min,the minimum value of 12kPa is reached,and the whole process is in a unsaturated state;3)The new drainage system can prevent water infiltration to the subgrade,and the suction of the subgrade soil has not changed,and is kept at initial suction value in the process of rainfall;4)Analysis of influence factors of new type drainage system shows that the new drainage system is arranged between the surface layer and the base and the base and the subgrade,which can effectively reduce the suction and water content of the surface layer and base.Increasing the thickness and slope of the new drainage system can reduce the suction and volumetric water content of the base.Numerical simulation and model test results show that by using the new drainage system,the base in the unsaturated state will start the drainage,the infiltration to the pavement structure of the water will eliminate the structure quickly and effectively,which reduce the amount of water in the pavement structure.And the new drainage system can prevent the water from the water to the subgrade,to ensure good pavement structure carrying capacity.