Research On Strength Formation Mechanism And Application Of Laterite Granule In French Speaking Area Of West Africa

With the gradual deepening of our country’s “One Belt and One Road” cooperation initiative,the road projects in West Africa have gradually increased.In West Africa,special road-building materials that are rare or even unavailable in our country,such as laterite granule,are widely distributed.The laterite granules have great variability in mineral composition and mechanical properties,and there is no universal clay performance standard in the local area.The research carried out material property analysis,mechanical performance analysis,numerical simulation test,strength formation mechanism analysis and engineering application recommendations for a variety of laterite particles in West Africa,aiming to provide a certain reference for road design and engineering construction.First,the mineral composition analysis,engineering classification,compaction test and CBR test and analysis of the natural laterite granule in West Africa were carried out,and compared with the laterite granule of our country.The results show that the West African laterite granule have the phenomenon of missing the median particle size in the gradation characteristics.The main mineral components of laterite granule are kaolinite,quartz and limonite,and their content is critical to the liquid-plastic limit and apparent appearance of soil.The results of CBR test and compaction test show that only part of natural laterite granule from West Africa can meet the bearing capacity requirements of subbase or cushion of French inverted pavement structure.Secondly,in order to improve the usability of laterite granule,cement stabilization method was adopted to improve the mechanical strength of laterite granule.Cement stabilized clay grain of unconfined compressive strength test results show some laterite aggregate value higher compressive strength comes from its fine particle content,cement stabilized clay dosage was 3.0% cement aggregate can meet in the west African country under light traffic level of road base materials under 1.5 MPa strength requirement,increase cement dosage can be applied to a higher grade road and layer structure.Then,based on the characteristics of particle size and cohesive properties,a virtual sample model and a mechanical test model of laterite granule were proposed,which were divided into coarse-grained soil and fine-grained soil.The parallel connection model and linear contact model were used to calibrate the connection parameters,and the virtual mechanical test of laterite granule was completed.According to the test results,the failure process of laterite granule under compression is analyzed from the meso-view,and the connection parameters of the model are established with the macroscopic mechanical properties of the material.It is concluded that the strength of laterite granule is mainly due to the combined effects of the mineral composition of parent rock,particle compaction and filling,cement hydration reaction and chemical excitation.Finally,based on the typical ground material of laterite granites in West Africa,traffic conditions and local economic development level,combined with the development experience of semi-rigid base asphalt pavement in China and the typical structure of inverted pavement in France,the optimization design of local pavement structure in West Africa was carried out.Asphalt gravel layer and stress absorbing layer are mainly used to solve the problem of crack disease and water damage of semi-rigid pavement base.French ALIZE software is used to check the thickness and determine the thickness of pavement structure layer.