Development And Application Of Real-time Quality Monitoring System For Highway Subgrade Compaction

The compaction quality of highway subgrade is the key to the long-term safe andstability for highway operation. The conventional quality control method of highwaysubgrade construction, which mostly depends on supervisors to control the rollingprocess, is difficult to ensure the construction quality because of the influness ofmannual factors. It’s easy to cause such problems as extensive management,insufficient or excess compaction. Furthermore, the conventional quality inspectionand assessment method of subgrade compaction primarily relies on samplingrandomly at job-site spots after compaction. But it may not reflect the real qualitysituation and usually causes unreliable representation of the compaction quality of theentire work area using limited samples. Meanwhile, the conventional method isdifficult to realize feedback control and delay on the construction schedule because oftime consuming of pits test. Therefore, it is necessary to research a real-time qualitymonitoring system for highway subgrade compaction considering with thecharacteristics of highway subgrade construction. It is extremely theoretical andpractical significant for not only ensuring the compaction quality, but realizing thetimely feedback control. The contents and achievements of the research are asfollows:(1) According to the requirements of construction quality control during theprocess of highway subgrade construction, the general framework and main functionsof the real-time quality monitoring system were designed basing on the developedpreviously system by our research-team. Thus, by using the technologies of GPS、GPRS and computer network technology, a real-time quality monitoring system ofhighway subgrade construction was developed in details. Employing the system, itrealizes precise control of the rolling trajectory and real-time monitoring on thecompaction quality, as well as the vibration frequency during rolling process. Inaddition, it overcomes the shortage of the imprecise manual control, and enables toensure the construction quality of highway subgrade effectively.(2) Correlation between the compaction value (CV) and the conventionalcompaction quality representation indices (i.e. compactness and dynamic elasticmodulus) were analyzed basing on the developed monitoring system, and came to theconclusion that there is a high linear relationship between the CV and the conventionalindices. Thus it provides a basis for establishing the quality evaluation models ofhighway subgrade quality.(3) According to above the correlation analysis, the quality evaluation models ofhighway subgrade compaction were established, including the compactness evaluationmodel and the dynamic elastic modulusevaluation model of subgrade soil material,which can be employed assess timely the compaction quality during rolling. (4) A fast assessment method for subgrade compaction quality of the entire workarea was put forward. According to the timely collected—CV, and the qualityevaluation models, and also using the Kriging interpolation, the compaction qualityat any location of the work area can be obtained, and then the qualification rate of theentire work area can be analyzed. The evaluation method can overcome the shortageof the insufficiency and the delay of pits sampling, thus provides a new way forreal-time quality control of highway subgrade construction.