| The engineering properties of rock fill and fine-grained soil fill are very different.The particle breakage rate is high during the compaction,and the particle size changes dramatically.As a result,the compaction and quality detecting technologies of stone filling subgrade and soil subgrade differ significantly.However,transportation departments’ research on concrete compaction control and quality detection has mostly relied on fine-grained soil for a long time,making it impossible to properly guide the construction organization and quality control of large-size stone filling subgrades.It is of theoretical significance and practical value to carry out research on numerical simulation,quality inspection and stability control of rock-fill roadbed compaction to improve its on-site construction efficiency and post-construction stability.The microscopic parameters of particles in the rock-filled subgrade model were determined by numerical and laboratory tests based on discrete element theory,and a numerical model of rock-filled subgrade was created to simulate the vibratory compacting process of rock-filled subgrade.The force chain system was discovered to be a dynamic process of continuous breaking and re-establishment under the load based on the change of particle force chain during the compacting process.From top to bottom,fine particles continued to move and collide in the skeleton structure constructed by large particles to form a weak force chain,and the strong and weak force chains were eventually joined to form a stable structure.The single variable analysis method is used to investigate the effect of vibration frequency,amplitude,and excitation force on the compaction effect of rock-filled subgrade.The influence of compaction parameters on the compactiing effect of rock-filled subgrade is quantified using the finite element numerical simulation approach.To simulate several compaction combinations,two regularly used levels of roller tonnage,excitation force,vibration frequency,and drive speed are used.The ideal compaction combination suitable for rock-filled subgrade is investigated,and it is found using the model’s effective compaction depth,surface settlement,and maximum tensile stress:28 Hz of the frequency,400 kN of the excitation force,4 km/h of the speed.The effectiveness of the combinations is confirmed by combining it with th e physical project.In the entity project,the porosity tested by irrigation method is utilized as a control index of subgrade compaction quality,and the portable drop hammer deflection instrument,nuclearfree density instrument,and heavy dynamic sounding are also used to control the compaction quality of subgrade.The empirical formula between test results of the aforesaid detection method and porosity is found,and feasibility of the empirical formula is confirmed by combining it with the test section.In order to better control the long-term stability of rockfilled subgrade after construction,the long-term monitoring of subgrade settlement,slope horizontal displacement and internal stress is carried out in order to timely warn and treat the possible diseases of subgrade,and ensure the long-term stability of rock-filled subgrade after construction.There is no early warning in each monitoring,indicating that the performance of the entity project is stable. |
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