Study Of Subgrade Settlement Laws Of High Fill Multistage Retaining Wall And Numerical Simulation About Stability

With the rapid development of China’s western construction, building heads for the mountain and valley. At the same time, these increasing problems of road stability bring new challenges for the design, construction and management. ShiMan highway is the west part of YinChuan-WuHan highway in Hubei Province, located south of Qinling Mountain, straddling two YunXian fault zone. It is no easy to build for the existence of landslides, collapses and other geological disasters in the area.In this situation, the study of the settlement of fill subgrade and stability of retaining walls has been carried on.We have chiefly fulfilled the following tasks:First of all, the roadbed settlement experiments have been carried on in the five sections of ShiMan highway where high fill and deep slope geological disasters is very common and serrious:(1) Subgrade settlement observation experiment has been carried on at the cross-section of K32+670 on the 4th section of ShiMan highway with the highest fill of 76 meters. (2) By section-settlement-meter, Subgrade settlement experiment has been carried on at the cross-section of K29+400～500 on the 3rd section of ShiMan highway with the highest fill of 27.5 meters.(3) Subgrade settlement monitoring have been carried on by settlement-pile, at three sections of K36+660～900, K47+500～600 and K47+700～900 of ShiMan highway. Study on the settlement laws of the high fill embankment has been made by analyzing the experiment results and settlement mechanism has been analyzed as well.Secondly, prediction models on high-filling subgrade settlement have been proposed. The settlement rate at different stages and the ultimate settlement have been predicted by four methods:logarithmic fitting, Asaoca, poisson curve and gray prediction model, based on the measured data of the fill roadbed settlement. Results of each prediction method are compared and analyzed.Thirdly, the laws of earth pressure distribution against the back of multistage retaining wall has been studied by burying soil pressure gauge and monitoring level and vertical earth pressure on the back of retaining wall at 5 levels. The level earth pressure-time relation curve has been drawn. Thus, earth pressure formula suitable for multistage retaining wall at mountainous areas has been established.Fourthly, laws concerning deformation, sedimentation and stability of multi-level retaining wall has been got by regular observations of retaining wall displacement changes at deformation observation points of level 1,2 and 4,18.Finally, numerical simulation on stress, strain and settlement of high fill subgrade has been carried out. Stress-strain and displacement settlement of two high fill cross-section (4K32+670 and K31+625) of ShiMan highway have been studied by Ansys and Marc software. The largest tensile stress and weakest part of cross-section of the roadbed have been found through simulation analysis. Analysis results of these numerical simulations are approximately consistent with the results of the observations on the spot.In summary, the results provide scientific guidance for the design and construction of the roadbed. At the same time, the settlement theory of high-filling subgrade also can be referred to as a reference for construction of road, railway, mining, dam, embankment, and so on.