Road Engineering Properties Of Metamorphic Soft Rock Used As Embankment Fillng In Qin-Ba Mountainareas And Vibration Compaction Technology Research

Freeway construction must be through the mountains and across the valley in Qin-Bamountain, therefore, a lot of metamorphic soft rocks such as tunnel, slope cutting andexcavation waste would be generated in the construction process, discarded materials needto be outward transported and piled up, the waste accumulation need to occupy the land andtake protective measures, in the meantime, there were existing lack of embankment fill, thetransportation road construction is difficult, the long distance borrowing soil is hard and soon, If to use gravel as embankment filling, must digging gravel from the river bottom, itwould destroy the river beds and the local environment. If the metamorphic soft rocks canbe used as embankment filling, not only reducing the cost of road construction, alsoprotecting the ecological environment, having obvious economic and social benefit.However, metamorphic soft rocks with adverse properties such as the strength would bereduced after wetting, weathering easily, compression crushing easily, after rolling coarseparticle filling grading of metamorphic soft rocks embankment changes greatly, wettingsettlement would occur with the influence of water, and uneven settlement would lead topavement structure uneven and reflective cracking disease etc, while whether metamorphicsoft rock can be used as highway embankment filling and it is not clear about compactiontechnology and testing standards for soft rock filling in the existing 《Specifications forDesign of Highway Subgrades》(JTGD30-2004) and 《Tcchnical Specification forConstruction of Hithway Subgrades》(JTGF10-2006). Therefore, the paper combined withscience and technology project of Western Transportation Construction《The key TechnologyResearch on Metamorphic Soft Rock Filler Embankment Construction in Qin-Ba MountainAreas》（2009318812004）, relying on Shi(Yan)-Tian(Shui) and Zha(Shui)-Xiao (He)highway construction, through the indoor experiments and field tests, combining withnumerical simulation and theoretical calculation analysis, studied deeply and systematicallyon road engineering properties test of metamorphic soft rock used as embankment filler inQin-Ba mountain areas, vibration compaction technology research and testing technologyspecification,the main results are obtained as follows: 1. By grinding and polarizing microscope experiment of rocks, in the highwayconstruction, carried out component analysis and naming of metamorphic rock；Studied theinternal structure composition of metamorphic rock and whether it contains hydrophilicmineral; Through the expansion experiment and resistant to disintegration tests, studied thefree and pressure expansion rate of metamorphic rocks, and cycle resistant to disintegrationindex law; Conducted point load strength test of metamorphic rocks in the dry and differentsoaking time condition, mading for four grade classification of metamorphic rocks point loadstrength, such as: the hard rock Is（50）≥5.0Mpa, relatively hard rock2.5MPa≤Is（50）<5.0Mpa,soft rock0.4MPa≤Is（50）<2.5MPa，exceedingly soft rock Is（50）<0.4Mpa，it can be seen, otherrocks are all soft rocks after water saturated in addition to felsic porphyritic mylonite schist;Point load strength can objectively reflect irregular rock strength after artificial broken in theactual engineering, avoided the problem of uniaxial compressive strength was higher thatcaused by selecting regular specimen from a large rock.2. Through compaction and shaking table test of metamorphic soft rock filling, based onthe work and energy principle, proposed compaction energy (compaction work) andvibrational energy per unit volume calculation formula,analyzed the energy size impact onmaximum dry density of metamorphic soft rock filling and its variation rule; obtained fillingmaximum dry density value when different coarse particle content in standard compactionenergy; By bearing ratio (CBR) test, analyzed the impact of the CBR value with compactionwork, got the filling CBR value with the compaction work and its changing rule, it provided abasis for evaluating highway filling engineering properties.3. Through indoor large-scale compression test，used single-line method,double-linemethod and cyclic loading method, studied wetting settlement rule of metamorphic soft rockfilling under different loading, respectively obtained wetting strain values under three loadingmethods and wetting settlement values of the corresponding loading filling height, andsuggested that the maximum filling height value. Using the principle of effective stress,according to the ratio of particle contact area and total area, combined with the compressiontest loading, estimated the contact stress between the particles. Adopted particle flow methodto simulate large-scale compression test of metamorphic soft rock filling，based on Hertz contact theory，under some hypotheses，got changing rule of aggregation internal particlestrong and weak contact force chain,porosity, mean contact force, maximum contact forceand displacement of the top particle compression, it provided an analysis method forexplaining interaction of filling internal particle in the compression test process.4. Through indoor large-scale triaxial test, studied stress-strain law of metamorphic softrock filling under four confining pressure in the dry and saturated state, analyzed theinfluence of the deviation stress and confining pressure with wetting strain, for embankmentfilling wetting settlement, based on different calculation steps,the single line and double linemethod are respectively realized in the finite element model, based on compiledDuncan-Chang model finite element subroutine,used the single line method and simulatedembankment wetting settlement under different working conditions, and compared withsettlemen of the indoor large-scale embankment loading test, the results show that,singlemethod can better response of embankment wetting settlement rule, field embankmentwetting settlement estimated value from indoor soaking-water loading test results can met thespecification requirements of embankment settlement.5. According to the basic principle of vibratory roller, based on the work and energyprinciple,derived vibration compaction energy per unit volume filling calculationformula,combined with compaction and shaking table test results,ensured the metamorphicsoft rock filling embankment compaction degree to meet the requirements of《Specificationsfor Design of Highway Subgrades》(JTGD30-2004), road roller vibration compaction energywould be greater than compaction energy (compaction work) and indoor vibrational energyper unit volume, through calculating vibratory compaction energy, and compared with theenergy value, then choosing the appropriate tonnage rolling machinery and strong vibrationcompaction parameters(loose lay thickness, rolling times, rolling speed and the wheel trackoverlap coefficient), through field test results verify the rationality and practicality of theformula calculation results, the formula provided a calculation method to select strongvibration compaction parameters.