Study On Collapsible Loess Roadbed Filling Engineering Characteristics And Slope Stability Of Yanchong Highway

When the collapsible loess is immersed in water,the soil structure will undergo significant additional deformation due to the self-weight stress or the combination of self-weight stress and additional stress.Based on the construction requirements of “zero-abandoning” of highway green engineering,when collapsible loess is used as highway subgrade filler,it may cause great damage to subgrade engineering.Therefore,its physical and mechanical properties must be studied and improved to meet Basic requirements for highway subgrade filling.The decisive factor in causing loess collapsibility is the water immersed in the soil.Therefore,to solve the collapsibility problem,it is necessary to study the permeability of collapsible loess and find an effective way to prevent external water from immersing into the subgrade soil,thus ensuring high speed.The stability of the highway subgrade slope meets the construction requirements of the highway quality project.Based on the results of geotechnical tests,the physico-mechanical properties of loess-like soils in Yanchong Expressway are statistically analyzed.The distribution characteristics of loess-like soils are analyzed.The variability of various physical and mechanical indicators and their causes are analyzed.On this basis,the engineering characteristics and slope stability of collapsible loess roadbed fillers are studied.The main research results are as follows:1.The engineering characteristics of loess and cement modified loess as roadbed filler were analyzed by indoor collapsibility test and direct shear test.The results show that when the loess-like soil is used as the roadbed filler,the compaction degree of the fill should reach 94% and above to eliminate the collapsibility;when the cement is mixed with 5%～6%,the improvement is made in the loess soil.When the embankment filler strength is ensured,the collapsibility can be further eliminated.2.Through the indoor penetration test and freeze-thaw cycle test,the anti-seepage and anti-freezing properties of cement modified loess as the lime seal were studied.The results show that the anti-seepage property of the improved loess is far superior to that of the unmodified loess,and the frost resistance provided by the cement to the soil after the freeze-thaw cycle has also contributed positively to the improvement of the anti-seepage property of the improved loess.3.According to the test results of soil strength and permeability coefficient,the stability of the collapsible loess embankment slope of Yanchong Expressway under different working conditions and the reinforcement effect of lime soil seal were analyzed by numerical calculation method.The results show that the compaction degree of the embankment filled in the current project is 96%,and the lower compaction degree of 94% is stable under normal conditions;stability under abnormal conditions of heavy rain or continuous rainfall Slightly worse,it is recommended to use 5% of the cement in the design of the anti-seepage ash seal of the loess embankment slope in the seasonally frozen soil area,which can ensure the long-term stability of the embankment under heavy rain or continuous rainfall conditions.The research results of this subject solve the problem of spoil reuse of the collapsible loess in Yanchong Expressway,improve the engineering quality of collapsible loess roadbed filling,and provide effective control for geological disasters of collapsible loess embankment slope.Measures to provide technical support for the safety of highway construction in the collapsible loess area of China.