| In agricultural water conservancy projects,drainage ditch at all levels are an important part of the irrigation and drainage system.The drainage ditch of farmland in Ningxia Yellow River Irrigation Area is affected by the soil texture and the alternating cycles of wetting-drying and freezing-thawing,so severe collapse and poor drainage have hindered the development of agriculture in irrigation areas.The collapse of farmland drainage ditch has become a bottleneck for sustainable agricultural development in Ningxia Yellow River Irrigation District.In this thesis,the structures of geotextile soil containers that the soils came from original soil of ditch slope and the bags made of geosynthetic new materials are used to lay out the small and medium-sized farm drainage ditch slopes in the irrigation area so that to treat the agro-drainage ditch in Ningxia Yellow River irrigation area and slope protection,and to explore the effective and suitable slope-lining process and technology.By carrying out indoor direct shear friction test of geobags and soil,long-term field prototype monitoring test,geotextile material degradation and durability test under saline erosion,the effect of slope protection with geotechnical bag and grass-soil willow pile,the friction characteristics between the geotechnical bag and the soil interface and the durability of the geotechnical bag were analyzed and investigated in the special service environment of the irrigation area.On this basis,according to the calculation principle of horizontal slice method,the horizontal slice calculation formula for the stability analysis of geotechnical bag masonry structure was derived.And the slope stability coefficients were calculated and analyzed under the four operating conditions inclusive of homogeneous soil slope,geotechnical bag masonry slope,homogeneous soil slope with flowing sand layer,geotechnical bag masonry slope with flowing sand layer,respectively.In addition,the stability of the slope with geotechnical bag masonry adding willow pile was simulated by using Geostudio Software to establish the numerical model under seepage conditions.Finally,AHP was used to comprehensively evaluate the slope-solidity effect.Mainly achieved the research results and conclusions as follows.(1)The test results of the interface friction characteristics of the geotechnical bag material and the ditch slope soil show that the shear strength of the interface between the geotextile and the geotextile increases first and then decreases as the water content increases,and increases as the compaction degree increases.The friction coefficient of the reinforced-soil interface increases first and then decreases with the increase of water content,and increases with the increase of compaction.The friction coefficient has a certain inverse relationship with the normal stress,and with the normal stress,the increase shows a decreasing trend.(2)Through the analysis of the test results of long-term prototype monitoring,the results show that:①The displacement deformation of the north and south slopes of the farm drainage channel shows the same change regularities,the displacement deformation at 30 cm is the smallest,and the displacement deformation at 120 cm is the largest.The displacement increases with the depth of the measuring point;②The slope deformation and collapse of the grass-soil willow pile test section are serious,the slope deformation and collapse of the geotechnical bag masonry test section are not obvious,and the data change is much smaller than the grass-soil willow pile test section.A good slope collapse prevention,and the long-term consolidation effect of the slope with geotechnical bag masonry is remarkable.(3)The test results of the durability of geotechnical bag materials show that:in distilled water and alkaline solution,the mass and thickness of the bag material per unit area change little,and the retention rate of breaking strength is above 99%and 97%,respectively,indicating that the polypropylene geobag material has good resistance to water immersion and alkali resistance;sulfate and chloride salts have a certain impact on the deterioration and durability of geotechnical bag materials.The greater the salt content of the solution,the more serious the degradation,and the sulfate salt has a greater impact on the erosion and degradation of the bag material than the chloride Significant;dry-wet cycle will aggravate the deterioration of the bag material,the salt solution will produce bursting force due to water evaporation and crystallization,and the deterioration will be more obvious.(4)In view of the advantages of the horizontal stripe method in the stability analysis of georeinforced materials,the horizontal stripe method is used to reflect the friction effect between the bag-soil and the bag-bag,and the stability analysis of the geotechnical bag masonry slope is performed.The formula calculation and simulation results indicate that the geotechnical bag masonry mode has no significant effect on the slope consolidation at the slope bottom existing soft layer for example quicksand.It is recommended that the slope without soft inter-layer at the bottom to treat with geotextile bags to protect,and in the case of weak inter-layers such as quicksand to treat with geotextile bags combining wooden piles support for agro-drainage ditch in the irrigation area.(5)The comprehensive evaluation of the geotechnical bag slope-fixing model is second only to the Gebin stone cage slope protection,and the comprehensive weight is not much different,but the environmental single factor index is 26.5%to 50.2%higher than other programs.It is recommended to try to summarize the engineering practical experience in the experimental demonstration of the geotechnical bag slope fixing scheme in the irrigation area,so that this technology will be applied gradually. |
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