Research On Load Reducing Effect Of Expansive Soil Cutting Retaining Wall By Inverted Filter

Expansive soil has the characteristics of expansion and contraction,which easily leads to instability of the retaining structure.If the filter layer can reduce the soil expansion pressure to a certain extent,it will be beneficial to the stability of the retaining structure.The traditional anti-filtering layer adopts bagged sand and gravel,which has the disadvantages of gravel bag yarding,long construction time,long slope exposure time,easy collapse and poor load reduction,etc.,and its main function is only reflected in the drainage of the filter.In expansive soil areas,the function of how to make the filter drainage layer flexible to reduce the expansion pressure needs to be further developed.If the reverse filter layer can exert a certain degree of load reduction,it will be very beneficial to the stability of the retaining structure.Therefore,in order to standardize and improve the design and construction of the anti-drainage drainage system for retaining structures,improve the construction efficiency,ensure the quality of the project,and fully and effectively exert the anti-filtering and drainage functions of the anti-filtering layer,develop a new load reduction function for the anti-filter cushion layer.Based on data and product investigations,geotechnical tests,material testing tests,finite element calculations,unit model tests,field tests,and theoretical analysis as the research methods,the matrix materials and structural forms of the main inversion layer at home and abroad were developed.Performance index,construction process,quality control measures,application status,industry specification and related research results;indoor geotechnical test work was performed to determine physical-mechanical properties of soil materials used in indoor unit structural model tests,using finite element values.Analytical methods,and validation of indoor model tests,given the reasonable thickness and modulus value of inverted filter drainage under load under expansive soil conditions;combined with finite element calculations,indoor test results and economic analysis,determine the new type of drainage drainage The system is adapted to the structural requirements,modulus,and thickness recommendations of different functionalities for reference in the design;field tests are performed to verify structural products.The main research results are as follows:(1)Under the working conditions of expansive soil cutting and retaining structure,a composite drainage reverse filter cushion layer with a certain thickness between the back of the wall and the soil has a significant load reduction effect.(2)The elastic working range of the composite drainage reverse filter cushion under the working condition of the expansive soil roller retaining structure can be set between 0 and 100 kPa.In consideration of ensuring the stability of the soil behind the wall,the maximum degree of play can be achieved.The reasonable performance index of the load-reducing effect of the composite drainage reverse filter cushion layer is: the appropriate range of modulus is about 0.1 MPa,and the suitable range of thickness is not more than 10 cm.(3)Combining the economical analysis of the material of the anti-filter mat layer,the indicator combination for the selection of product type for the expansion soil pile-pile wall is: 2cm+0.1MPa(load reduction rate of 52%),4cm+0.15MPa(load reduction rate of 62%);Expansive soil gravity retaining wall conditions for product selection indicator combination recommended as: 2cm+0.05MPa(load reduction rate of 26%),4cm+0.1MPa(load reduction rate of 28%),different workers Specific indicators under the circumstances should also be comprehensively determined in combination with economic analysis.