Study On Shear Strength Characteristics Of Improved Loess With Recycled Aggregate Of Construction Waste

With the acceleration of urbanization in China,large scale urban demolition and reconstruction in the northern loess region has produced a large amount of construction waste,which leads to environmental pollution and waste of space resources.The main reason for this phenomenon is the lack of a complete construction waste management system,no economic and scientific disposal means.At the same time,the development of the western region requires a lot of infrastructure construction,such as road construction and bridge building.The filling of highway roadbeds consumes a large amount of fillers.If they are completely filled with pure soil,not only the only cultivated land resources will be destroyed,but also the design of such roadbeds will be difficult.Reasonable recycling of construction waste can not only solve the environmental problems,but also more importantly realize the recycling of resources and avoid the waste of stone resources.A large number of studies have shown that construction waste can be recycled after being processed through certain processes.Therefore,it is of great engineering significance and social value to study the shear strength of the mixture formed by loess and construction waste.In this paper,the clay bricks and concrete in the construction waste are treated as aggregates and form a yellow-solid mixture with the loess.The basic physical and mechanical parameters of the loess and aggregates are obtained through the geotechnical test.Then,a specific test plan was developed to conduct indoor direct shear tests,and the test parameters such as the ratio,particle size,and normal stress of the recycled aggregate were studied.Finally,using FLAC3 D software for numerical simulation,and combining with the direct shear test data to make a comparative analysis.The main results are as follows:1)When the normal stresses was respectively 50 kPa,100 kPa and 200 kPa,the development trend of the shear stress-shear displacement curve of the mixture is consistent with the proportion and particle size of the recycled aggregate blended into the loess.In the shearing process,the mixture initially appears to be approximately linear.During this process,the shear stress rapidly increases up to the peak value,followed by a significant falling segment.Finally,the residual stress causes a steady decline in the rate of decline due to residual stress.The whole process can be divided into three stages: compression yield stage,shear failure stage and residual stress stage.2)Adding recycled aggregates to loess can improve its shear resistance.As the content of recycled aggregate increases,the shear strength of the mixture increases,and the changes in cohesion and internal friction angle increase firstly and then decrease.With the change in the size of the recycled aggregate,the shear strength of the mixture is also increasing.At this time,the changes of cohesion and internal friction angle were still increase firstly and then decrease,and the change trend of internal friction angle is more obvious.3)The shear resistance of loess varies with the content and particle size of recycled aggregate.When the aggregate of clay bricks was added,the ratio was 4:6 and the aggregate diameter was 2.5 ~ 5mm,and the shear strength of the mixture was the best.When concrete aggregate is added,the ratio of yellow to solid is 4.5:5.5 and the grain size of aggregate is 5-10 mm,and the shear resistance of the mixture is the best.4)When the normal stress was respectively 50 kPa,100 kPa,and 200 kPa,the shear strength of the mixture incorporating clay brick aggregates increased by 33.5%,34.8%,and 35.5%,which relatived to the pure loess;the shear strength of the mixture combining concrete increased by 45.5%,62.9% and 75.3%.5)The numerical simulation results of FLAC3 D software are consistent with the curve of the test results,which also proves the rationality of the test results in this paper.