Research On The Application Technology Of Large Particle Size Non-cohesive Earth-rock Mixture Filling Roadbed

In mountainous and hilly areas,there is a lack of fillers and road transportation is difficult,and large particle size non-cohesive soil-rock mixtures produced by road cutting excavation and tunnel blasting exist in large quantities.These large-grained non-cohesive soil-rock mixtures bring challenges to road engineering construction and testing applications due to their large filler size,a small amount of fine material,and heterogeneity.How to choose reasonable construction technical parameters in order to achieve optimal compaction has become the application of this type of filler in the urgent need to address the key issues.This thesis relies on the reconstruction and expansion project of the Lai（Wu）-Xin（Tai）second bidding section of the Beijing-Shanghai Expressway and conducts systematic and refined research on the physical and mechanical characteristics of large-particle soil-rock mixtures,the parameters of large-particle size rock placement,the law of settlement change,and the application of on-site construction technology through indoor physical mechanics tests,indoor model tests,numerical simulations and theoretical analysis,etc.The main research contents are as follows:（1）The basic physical and mechanical properties of large particle size non-cohesive soil-rock mixtures are revealed:The mass of the sand group is less than the mass of the gravel group in the large particle size soil-rock mixtures distributed along the project line,and the content of fine-grained soil is less than 5%of the total mass,the unevenness coefficient Cu and curvature coefficient Cc are 31.92 and 1.26respectively,which are well-graded gravels;in the soil-rock mixtures,the rock samples as a whole showed yellowish brown-grayish white,and their The main mineral composition is quartz and feldspar respectively,and the content of Si O₂ is 16%（less than 52%）,which is alkaline stone（calcareous）;the best moisture content of large particle size soil-rock mixtures is 5.2%,and the maximum dry density is 2.054 g/cm~3,the change of water content has a great influence on the compaction of soil-rock mixtures,and the subgrade filling process should strictly control the moisture content to make it reach the specified compaction.The CBR value of the soil-rock mixtures is63.2,which is much larger than the specification requirement;the density of large particle size block stone is 2.75 g/cm~3,and the uniaxial compressive strength in the natural state and saturated state are 77 MPa and 55.8 MPa,which belong to medium-hard rock.（2）The settlement variation law of the subgrade containing large particle size stones was refined,and the best placement parameters of large particle size stones were obtained:the best placement spacing of large particle size stones inside the soil-stone mixtures embankment was obtained by indoor visualization model test and advanced micro digital camera visualization tracking technology,and the suitable burial depth was below 2 m from the top surface of the subgrade,and the stone size was in the range of 40 cm-60 cm,with the increase of particle size,the stability of the subgrade is better.（3）By establishing a particle flow discrete element model for large particle stones to fill the subgrade,the accuracy of the optimal spacing and appropriate burial depth of large particle stones was verified,and it was confirmed that large particle stones were vertically arranged inside the subgrade.It is advisable to use the dislocation arrangement.（4）Based on the optimal placement parameters of large particle stones inside the subgrade,a finite element model of the actual subgrade was established,and the vertical and lateral stability of the subgrade was compared with that of the subgrade without large particle stones under the vehicle load,and the deformation of the subgrade was mainly in the vertical direction,and the maximum and minimum settlement of the pavement with large particle stones inside the subgrade was lower than that of the subgrade without large particle stones.The stability of the pavement with large particle stones is better.（5）Based on the placement parameters of large particle stones determined by laboratory routine tests,model tests and numerical simulations,the sorting and placement of large particle stones in the construction process,the paving,leveling and rolling of soil-rock mixtures are designed.And the construction inspection of the large particle size soil-rock mixtures subgrade,summed up the construction precautions of the large particle size soil-rock mixtures embankment.