Tram Embankment Load Characteristics And Construction Design

With the revival of tram in the world and the integration of high-tech elements in modern tram, we have much re-understand about tram. In our country the modern tram project has just started. There is a big difference about the train structure, speed and train axle load between the modern tram and traditional rail transit, so the traditional rail transit technique cannot be introduced into the modern tram engineering directly. What’s more, there is no identical design code of tram, so the subgrade structure of domestic modern tram needs to be urgent researched.Compared with the traditional rail transit, tram axle load is smaller and driving speed is slower. But the design method of the project of the tram reference to the design method of the traditional rail transit or high speed railway. Even some design parameters are directly used high-speed railway design parameters which may be too conservative. In this paper, theoretical analysis, numerical simulation and field test method are used to analyze the load characteristics, the roadbed structure, the settlement and the dynamic stress distribution law of tram. The main results of this paper are as follows:(1) Based on the calculation of composite beam on the Winkler elastic foundation, the distribution length of subgrade surface load is from 7.231mm to 9.410mm. The transverse distribution form is approximately uniform distribution, and the distribution width is the same as the support layer.(2) The subgrade surface load can be determined according to the design code of high-speed railway, and the subgrade structure can be determined by strength and deformation control of the design code of high-speed railway.(3) Numerical analysis shows that the tram subgrade consolidation settlement mainly from the foundation, foundation settlement accounts for 98% of the total settlement. Subgrade surface longitudinal distance distribution is about above 12m, which is larger compared to the theoretical calculation. Transverse dynamic stress distribution was "saddle", subgrade dynamic stress attenuation speed is faster than that of the high-speed railway, and the dynamic stress amplitude is much smaller than that of the high speed railway, the tram subgrade dynamic stress amplitude is about 42% high-speed railway.(4) The field test shows that the settlement and dynamic stress of tram subgrade are in agreement with the numerical calculation. The design method of tram using high speed railway standard are conservative, the tram subgrade bed thickness and subgrade compaction standards can be further optimized.Combined with our country having built the trams, the numerical calculation and field test in this paper, Tram subgrade surface vertical design load use evenly distributed load, in the design of the trams,subgrade structure and compaction standard should be further optimized.