Study on Continuous Compaction Quality Control of Rock Fill Embankment
|School||Southwest Jiaotong University|
|Keywords||Rock-fill embankment vibration compaction quality control continuouscompaction control|
With rapid development of China railway construction, crushed stone is used more and more in roadbed construction, especially in mountainous areas of southwest China. Compaction problems of embankment filled with crushed stone has not been resolved satisfactorily. People lay more and more attention to the compaction quality assessment now, so, the compaction quality assessment is an urgent problem in railway construction. In this thesis, on the basis of "Key technique study of Guiyang-Guangzhou railway hard rock filling embankment", continuous compaction technique is applied to control the compaction quality of rock-fill embankment and compared with conventional test indexes to establish the interrelated correlation.Traditional compaction test is man-made stochastic sampling, it’s "point" spot-check which will cause leak sampling besides "weak point" with poor representational difference, meanwhile, traditional methods are time-consuming, which bring about unfavorable effects to embankment structure. Combined with practical engineering, SA, SB, SC rock-fill material are selected to fill embankment layer to layer and section to section, after filled one layer, vibration roller compaction device is used, in the compaction process the continuous compaction parameters are collected (degree of compaction:Compaction Meter Value/CMV), after compaction procedure, precise leveling instrument is adopted to measure the embankment displacement, then settlement percentage of each layer is obtained. Known by the results after data processing, settlement percentage and CMV have great corresponding relation, namely settlement percentage decreases and CMV increases along the increase of roller compaction, and finally they tend to be stable. When roller compaction differential settlement is less than3mm without obvious wheel impress, stop compacting and detecting compaction quality routinely. The routine detect indexes are coefficient of subgrade reaction K30and K60, dynamic deformation modulus Evd and degree of compaction K, if those indexes meet the minimum value of current specifications, so the current compaction indexes can meet the requirement of roller compaction. Then relevance analysis is carried out for continuous compaction parameters CMV and routine detect indexes, the results show that the three rock fill material CMV and routine detect indexes have great correlation, which illustrates the feasibility applying continuous compaction technique in quality assessment of rock-fill embankment. Through analysis of continuous compaction results, the corresponding the typical value, RMS error and coefficient of variation are obtained, which illustrate the homogeneity of compaction quality meets the requirement. Coefficient of variation is a token index of data distribute degree, yet, variation coefficient of routine detect indexes is comparatively large, variation coefficient of continuous compaction parameters is comparatively small that is to say continuous compaction parameter is more suitable for large grain size rock-fill embankment.Finally, in connection with characteristics of continuous compaction detect and principle of mathematical statistics, Minitab software is applied to normal approach index distribute, from the probability point of view, set the confidence coefficient to0.9, then obtain the corresponding quantile data of indexes. Form the failure probability point of view, mass number Q is adopted to control the continuous compaction quality of embankment. From characteristics of continuous compaction, better quality acceptance scheme and recommend measure are raised, which could be references of engineering application.