Analysis For Abrupt Reinforced Embankment Stability And The Performances Of Culvert

The slope slide and culvert collapse are two prominent problems in abrupt high embankments of high-way engineering, combined with the subject "The application and mechanism of the reinforced soil with geosynthetics" from the Science Committee of Hunan Province, and "Study on Culvert pipe crack in highway engineering" from the Transportation Department of Hunan Province, the stability of abrupt embankments reinforced with geosynthetics and the mechanics performances of culverts were investigated in this paper. The main works include as followed:(1) Direct shear tests were run on low-liquid limit sand silt reinforced with four various types of geosynthetics to investigate their strengths and deformations to imitate the shear performances of reinforced slopes. Results showed that geosynthetics reinforcements modified the stress-strain behaviors of soil, which the peak shear strengths increased and arrived at larger shear displacements, the amount of reduction of residual strength was limited. As a result, the stress-strain curves flowed gentlely and the collapses of the reinforced soil became more flexible and ductile. The influence parameters concerning in the paper included reinforcement layers and modulus, soil compactness, as well as the surrounding pressure of test.(2) A finite element model to analyze stability of abrupt embankment reinforced with geosynthetics was established, and the stability and the influence parameters such as reinforcement modulus and layers, and the strength index of soil were investigated. The calculations had good agree with the results of direct shear tests and the observed in the centrifuge tests, which showed the calculation model and results reasonable.Results showed that reinforcement strengthened greatly the slope stability, as compared with the soil embankment, the stability factors, the critical heights and critical slope angles of reinforced embankments increased greatly, and the reinforced slope also had more ductility, which had good agreement with the tests in the paper. The highway engineering was always confronted with application of high embankment, meanwhile, must be with abrupt slope to decrease filling and occupying cultivated area, this always dropped the highway engineering in the dilemma, Obviously, reinforced embankment explored a way to this problem.Calculations indicated that the match of reinforcement modulus and soil modulus in some range, and the compatibility of the relative strength and stiffness ofembankment and subgrade would improve the reinforcement effects and contribute to the slope stability.(3) From material characteristics, structural performances and construction methods, the reasons of the cracks of reinforced concrete culvert pipe were investigated, and an improved technologic process including tests, manufacture of reinforced case, prefabrication, maintenance, the management of basement, joint and fill was proposed to reduce the initial cracks, the practical engineering indicated its effectiveness and feasibility.(4) A finite element model was presented and a calculation program was developed to investigate the mechanics performances of culvert pipe under reinforced and unreinforced embankments, and the calculations had good agreement with the measured data.Results showed that the stress behavior in soil-conduit system differed greatly from that in elastic halfspace homogeneous earth, around conduit existed various earth pressure concentrations due to the soil-structure interaction. Reinforcement adjusted the soil stresses surrounding the culvert, and alleviated the soil pressure concentrations on the top and bottom of culvert, meanwhile reinforcement increased the strength and stiffness of soil and the global stability of embankment, and this strengthened directly the arch effect of soil. As a result, the mechanical performances of the culvert were improved greatly. Reinforcement proposed an effective way to slow down the vertical pressure on culverts in highway engineering.(5) The various structural design methods of the culvert pipe in three sorts of code were investigated, and a new approach with consideration of the soil-conduit interaction was proposed in this paper. The comparisons of the calculations with laboratory test results and engineering condition surveys indicated its reasonability.Analysis showed that by U.S.A Code and Railway Code, the maximum calculation bending moments (b.m.) of culvert pipe had good agreement with that of tests, and the methods were relatively reasonable; By the Highway Code design method, the calculation b.m.s were smaller than test results, and the designs were unconservative relatively; As compared with the methods used currently of structural design methods of culvert pipe, the method considering the soil-conduit interaction could reflect the influences on the mechanical performances of structural properties and the surrounding soil, and was more reasonable in theory.A further discussion about this method was carried out in this paper, and the interaction performances of the buried structure and their influences on the internal...