Research On The Construction Workmanship And Pavement Performance Of Utilizing Tunnel Debris For Expressway Subgrade Construction

With the rapid development of highway industry,the construction of expressway gradually extends to the western area of China and the bridge and tunnels takes an increasing percentage in the construction.Presently,the utilization of excavated tunnel debris is not efficient due to the limitation of construction conditions.The dumped tunnel debris creates pollutions to environment and is a waste of resources.Dumping of debris that should have been utilized for subgrade filling not only do harm to ecological resources but also increase expenses for material haulage,revegetation and environment protection etc.Therefore,it is of great importance to utilize these debris for subgrade filling.To sufficiently utilize natural resources and avoid extra waste of space,we can utilize the debris as filling material for subgrade construction.The major composite of these debris are gravelly soil.Practices shows that coarse stone debris detonated from tunnel and processed by crushing can remarkably improve the bearing capacity and stability of subgrade.This paper researches the utilization of crushed stone as filling material in the project,analyzing the pavement performance of crushed stone,the workmanship of subgrade construction and the construction quality control method.The major research content and conclusion is shown below:(1)Summarize the characteristics,classification criteria,physico-mechanical index,particle structure and interaction between particles of gravelly soil.It adopts the indoor test to research the pavement performance of crushed stone filling materials.Research shows that: the unconfined compressive strength is in direct proportion to cement content and the water stability approaches a definite value;the CBR of filling materials is in direct proportion to compaction degree and filling depth;rebound modulus is greatly influenced by cement content,moisture and compaction degree.(2)Determine the construction scheme for trail section according to the project characteristics,adopt and implement appropriate construction method.Control the construction quality by test in site and decide design indexes for the project.The best design index for crushed stone filling material is : particle diameter not over 15 cm,lay-down thickness of 40 cm,rolling by not less than 4 rounds and compactness ranges94%~98%.(3)Implement the numerical simulation of layer-by-layer filling for trail section by ABAQUS software.The simulation shows that: the subgrade settlement is symmetrical along the axis of subgrade and increases as the filling depth increases.the proposed formula matching uneven settlement distance is(10)(28)08.0464.0BHL which is verified the feasibility of the formula,the maximum principal stress is in direct proportion to the elasticity modulus.