Study On Synergistic Effect Of Geogrid Reinforced Soil In New And Old Road Stitching

Along with the rapid development of economy, accelerated urbanization process, quickening urban population aggregation and increasing traffic volume, some of the early road construction cannot meet the demands of the increasing traffic volume increasingly, so it is necessary to transform the existing old roads. Throughout the splicing engineering of new and old roads in our country, the geotechnical material technology has already been widely used, but the theoretical analysis lags far behind the engineering practice in the layer number of geotechnical materials, location inconsistency and study depth. Aiming at a synergistic effect of geogrid on the splicing engineering of new and old roads, the paper conduct a research and deeply analyzes the relevant characteristics and disciplines of stress and deformation, and main work is as follows:1,Based on a stress analysis of reinforced soil, a riction reinforcement principle is discussed, which is given priority to a friction effect. According to a limit balance principle of reinforced soil, the analytical judgment is conducted for the stress characteristics of fracture and friction. Then, a new method to of stop-type geogrid reinforced soil is put forward to improve the anchoring force between soil and geogrid. It also analyzes the stress Characteristics of the stop-type geogrid under the effect of drawing, and obtains a formula to calculate the drawing resistance of the stop-type geogrid.2, based on the main problems in the splicing of new and old roads, the paper has carried on a theoretical analysis from three aspects, including the additional splicing stress, influences of geogrid on stress and displacement, and splicing settlement calculation. The analysis shows that the splicing settlement mainly comes from the foundation settlement of new splicing roads, and a formula is conducted, in which the post-construction settlement of new splicing roads= the total settlement of centre of form of new splicing roads within the reference period-(the settlement caused by old road load here+the consolidation settlement under load during the construction of new splicing roads).3, the paper carries out the calculating and analyzing of finite element for the tension of the stop-type geogrid and ordinary geogrid. On this condition, it analyzes the distribution characteristics of soil stress and displacement field, distribution characteristics of the tension in different displacements and the friction resistance in reinforced soil surfaces, and calculation results and theoretical values, and concludes that with the same embankment height, when the tensile displacement is greater than 2mm, the anti-tension and limit-deformation effects appear gradually; and when the embankment height is not more than 4m, the stop-type geogrid is more than ordinary geogrid in drawing resistance(anchoring force) by about 50%;and the reinforcement anti-drawing is improved by increasing the elastic modulus of stop-type geogrid; and the friction resistance in reinforced soil surfaces increases gradually from the tensile end toward inside, and achieves the peak.4, the paper carries out the calculating and analyzing of finite element for the roadbed stress and deformation characteristics, as well as the reinforcement effect, layer effect and width effect of geogrid in different conditions in the experiment cross section of new and old roads, and concludes that the smallest vertical displacement is in the center of old roads, the largest one is in the splicing center; and the horizontal displacement increases with the increasing of splicing height. The roadbed geogrid can slow the slope difference mutation in splicing, improve the integrity of old and new roads, limit the roadbed of embankment effectively, and reduce the soil pressure difference; and the number of geogrid layers has little impact on reducing roadbed uneven settlement; under the same splicing height, the stop-type geogrid width is only a half of the ordinary geogrid width, which meets the needs of practical engineering.5, the paper carries out the field test work of the splicing engineering, and researches the characteristics and rules of stress and deformation for the stop-type geogrid and ordinary geo-grid, the influence of different layers and widths on the synergistic effect. The results show that the geogrid has an obvious inhibitory effect on uneven settlement among roadbeds, especially the largest vertical displacement of stop-type geogrid decreases by about 35%; and the increased width has little effect on reducing the vertical displacement; under the condition of the same displacement, the stop-type geogrid width is only a half of the ordinary geogrid width., and the former’s strain value is greater than the latter’ due to anchoring force. The top-type geogrid can significantly improve the anti-deformation ability of road, in which the top flexure can be reduced by 15%. Comparing field test results with the results of numerical analysis, the stress characteristics, deformation rules, reinforcement effect, layer effect and width effect are consistent basically.6, according to the fracture mechanics theory, the stress-strain field of singular element simulation crack tip is introduced, and the calculation model is set up. This paper analyzes the geogrid anti-cracking effect in splicing under the action of the partial traffic load. The results show that the uneven settlement has significant effect on the bottom layer tensile stress and can reduce it for anti-cracking; the largest tensile stress is in the asphalt road surface, and the road base level is prior to the surface in cracking, so it is the best to lay the geogrid in the basic level top.7, based on the analysis and study of the design standard and construction technology for the uneven settlement in the splicing engineering of new and old roads, the design requirement of "double control" is put forward, namely the incidental tensile stress of the basic level underside is less than the splitting-strength of base material, and the uneven settlement slope-changing slope rate is less than 0.52%.