The Research Of Construction Technology For Subgrade Widening Of Liu-Nan Highway

With the growth of the economy in our country, the demand for traffic and transportation is constantly expanding. The existing highways can no longer meet the demand of rapid traffic development; therefore, massive highway reconstruction and expansion is still popular. Highway widening is different from highway construction. But the study of highway reconstruction in our nation started late, and relevant technology is relatively poor, lacking advanced construction techniques and quality control methods. Special geological section is the weak part in the widening reconstruction, not only should construction technology be taken into consideration in the design, but also its particularity be analyzed during the construction process, so as to improve the integral strength and stability of the special subgrade.This paper discussed construction technology in subgrade widening engineering, based on the project of the acceleration and deceleration lane extension of West Liujing traffic hub in Liuzhou-Nanning Highway.1. Through studying domestic and foreign researches, three kinds of test road projects had been designed. Settlement observation, compaction detection and quality test were conducted respectively, and a suitable construction technology and quality control method was proposed for subgrade in high liquid limit soil district.2. With the experimental analysis of the subgrade filling, it was found that the maximum dry density and optimum water content obtained by the wet standard compaction test was better as the quality control standard.3. Settlement and displacement on broadened subgrade was calculated by FLAC3D, settlement difference and horizontal displacement were minimal in test road project 2, which was consistent with actual measured data, indicating the feasibility of test project 2 for widening subgrade in high liquid limit district.4. After analysis of the test road program, it was concluded that the suitable construction technology and quality control methods for subgrade widening construction in this high liquid limit soil district, using 22t roller:static pressure 1 time, strong vibration 3 times, and static 1 times; or 30t roller:static pressure 1 time, strong vibration 2 times, and static 1 times.Therefore, based on the acceleration and deceleration lane extension project of traffic hub in Liuzhou-Nanning Highway, construction technology and control methods for widening subgrade was proposed, providing reference for the reconstruction techniques of expressway.