| Warping dam foundation is a kind of typical soft soil subgrade.According to its characteristics,after using conventional subgrade construction methods,there are often some defects such as post construction settlement,unstable slope and vehicle jumping at bridge head,which affect the normal highway transportation.As a representative of filling material for ultra light roadbed,foamed lightweight soil has the advantages of light weight,high strength,self setting and strong pumping capacity,and it can fully meet the basic requirements of the foundation of the warping dam.In this paper,foamed lightweight soil material is selected as the research subject,and foam and foam stabilization system is selected.The influence of water cement ratio,types and proportions of admixture on the properties of foamed lightweight soil is studied.Combined with long-term durability test,the ratio of lightweight soil materials is comprehensively verified and optimized,and the best matching ratio and process are obtained.On this basis,the construction of the supporting project is carried out,and the long-term monitoring and evaluation of the post construction characteristics of the materials are carried out.In this paper,the foam and foam stabilization system of foamed lightweight soil is studied firstly.The results show that only using surfactant as foaming agent can not form a stable and stable foam.According to the mechanism of foaming and stabilizing foam,the experiment combined many mechanisms together,and finally optimized the foaming system as follows:Twelve alkyl sulfate(4g/L)+ silicone polyether emulsion(0.8g/L)+ sodium chloride(30g/L)+ hydroxyethyl cellulose(1.7g/L),the final unit volume foaming capacity is 720 m L,and the foam half life is 75 min,which has relatively good foaming volume and stable foam effect.The effects of parameters such as the parameters of foam lightweight soil cementing material,water cement ratio,admixture characteristics and pouring height on the properties of foamed lightweight soil materials were studied.The results show that: when the water cement ratio is 0.5-0.65,the fluidity is between 160-200 mm,which can meet the construction requirements;through optimizing the proportion of admixture,it is found that a certain amount of saline soil can play an effective role in activating the fly ash material.The optimal proportion of saline soil and fly ash(0.3:1)and the range of admixture are determined.Through the influence of maintenance conditions and pouring height on the performance of light soil,it is found that the appropriate increase of temperature can effectively improve the maintenance effect of light soil,and it is determined that the direct pouring height during construction pouring is not more than 1 / 4 of the total height of the structure..Based on the optimization results of mixing ratio,three durability properties of light weight material,such as water stability,dry shrinkage and freeze-thaw cycle,were tested.The optimum weight and corresponding proportioning of foamed lightweight earth material were determined by durability results.The mass ratio of admixture to cementitious material was 40%,and the selected construction density was 800kg/m3.Based on the foundation works of a certain warping dam in Shanxi,the engineering application of foamed lightweight soil materials was carried out.From the selection,construction,quality control and later monitoring of the foam lightweight soil equipment,a representative cross-section was selected to complete the roadbed earth pressure,back pressure,roadbed and road surface settlement monitoring and deflection detection.The force meets the requirements of the warping dam subgrade and the lateral pressure on the abutment back Force,post construction settlement and pavement deflection can meet the application requirements of supporting projects,and have good economic effect.. |
PDF Full Text Request