| With the reconstruction and expansion of expressway,a large number of inorganic recycled materials(the original pavement base is cement stabilized material,and the inorganic recycled materials after milling are referred to as ’ water stabilized milling materials ’)are produced in the process of road widening.In the past engineering practice,it is often discarded,which not only wastes materials,but also pollutes the environment.At the same time,the problem of ’ bridgehead jump ’ caused by uneven settlement at the transition section of road and bridge seriously affects the driving safety.Therefore,in the process of highway reconstruction and expansion,the application of reclaimed water stable milling material to abutment backfill is considered to solve the multiple problems of road-bridge transition section.However,as a new type of abutment backfill,the performance evaluation index and standard of reclaimed water stabilized milling material are not clear,the construction technology is not mature,its settlement characteristics and mechanism have not been revealed,and the differential settlement mechanism between it and abutment,old abutment and new subgrade is not clear.In view of the above problems,based on the reconstruction and expansion project of Jingtai Expressway,this thesis makes an in-depth study on the performance of reclaimed water stabilized milling material as abutment backfill,analyzes the basic physical and mechanical properties of reclaimed water stabilized milling material and reclaimed water stabilized milling material,optimizes the material composition and construction technology,studies the settlement development law of abutment backfill section of reclaimed water stabilized milling material,and puts forward the comprehensive treatment measures for differential settlement control of abutment backfill section.Finally,a complete set of technology for abutment backfill of reclaimed water stabilized milling material is formed,which greatly reduces the differential settlement and effectively solves the problem of bridgehead bump.It has good social,economic and environmental value.In order to study the physical and mechanical properties of recycled water stabilized milling materials,on the basis of mastering the basic physical and mechanical properties of water stabilized milling materials,the curing mechanism and influencing factors of cement recycled water stabilized milling materials were clarified through relevant mechanical tests and microstructure analysis.The results showed that the water stabilized milling material had good gradation,small natural water content,large water absorption,high mineral powder content and a large amount of residual cement mortar.The water-stable milling material had a good loadbearing ratio,and its load-bearing ratio reached 157 %,which was superior to the performance of the abutment backfill.According to the results of compressive strength and splitting strength test,the cement dosage of reclaimed water stabilized milling material should not be less than2 %,and according to the results of dry shrinkage test,the cement dosage should be less than3 %,and the recommended cement dosage was 2 %.The compressive backfill modulus of the recycled water stabilized milling material with 2 % cement was 2677.2 MPa.The frost resistance of the recycled water stabilized milling material was good,but the dry shrinkage performance was worse than that of the new water stabilized material.In order to study the settlement performance of reclaimed water stabilized milling material as abutment backfill,the structural models of foundation,embankment,pavement,abutment and slope on both sides were constructed by theoretical analysis and numerical calculation method.The strain and stress characteristics of the key parts of abutment back in the transition section of road and bridge were analyzed,and the settlement,displacement and stress characteristics and development law were studied.The results showed that the use of reclaimed water stabilized milling material as the backfill material of the abutment back,the stress was large in the middle and small on both sides,resulting in a more significant soil arch effect,which effectively reduces the stress of the slope and the overlapping position of the new and old roads,and greatly improved the stability of the roadbed.The increase of subgrade settlement in the backfill section of reclaimed water stabilized milling material was mainly concentrated in the first 30 days,and then the settlement tends to be stable,which was about 20 mm smaller than that of conventional subgrade soil.As a backfill material,it can effectively alleviate the uneven settlement of the transition section of the road and bridge and enhance the anti-slip ability of the road.In order to study the backfill settlement characteristics of the back of the reclaimed water stabilized milling material in the entity project,the settlement field monitoring of the key parts of the back was carried out,and the development law of settlement deformation was analyzed.The test results were compared with the theoretical analysis and numerical calculation results to verify the feasibility of the numerical calculation and enrich the research content.The results showed that the longitudinal settlement of the road increased gradually from the back of the abutment to the direction away from the back of the abutment,and the closer to the slope,the greater the settlement of the slope at the same cross-section position.The settlement prediction curve was well fitted with the simulation results of the finite element software.Compared with the exponential model,the hyperbolic model has higher fitting degree and smaller residual error for the settlement of each monitoring point,which was more consistent with the field monitoring results.In order to study the treatment measures of differential settlement in road-bridge transition section,the construction technology suitable for reclaimed water stabilized milling material was summarized.The common control technology of differential settlement in road-bridge transition section of highway road widening section was analyzed.The construction technology of reclaimed water stabilized milling material as abutment backfill was studied,and the comprehensive treatment measures of abutment backfill differential settlement were put forward.The results showed that when the reclaimed water stable milling material was used as the back filling material for the back filling of the abutment,the compaction degree of the subgrade should be strictly controlled,the overlap between the new and old subgrades and the overlap between the backfill section and the conventional subgrade should be handled well to avoid seepage,and the construction quality of the slope and the cone slope of the abutment should be strictly controlled when there is more rain in summer.The TZSG-4 section of the reconstruction and expansion project of Tai ’an-Zaozhuang(Lusu boundary)section of the Beijing-Taiwan Expressway treated the differential settlement of the road-bridge transition section.The measures include: setting the bridgehead slab,filling the abutment back with recycled water stable milling material,strengthening the layout of drainage facilities,setting steps in the splicing section,improving the compactness of the subgrade and setting two-way geogrids.The application effect is good,which can effectively solve the problem of differential settlement in the road-bridge transition section. |
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