Research On Quality Control Of Cement Stabilized Crushed Stone Base Course Under Vertical Vibration Compaction

For the implementation of water-stable layer roadbed pressure,reaching the compaction strength standard and ideal uniformity has been the standard for quality control and acceptance for many years.On the one hand,both the core drilling test and the deflection test are carried out at limited points after construction,and the results are used to judge whether the entire rolled layer has reached the compaction standard,which is not convincing;on the other hand,Compaction quality inspection methods are complex,time-consuming and labor-intensive,and remedial measures are either impossible to complete or expensive when the construction has ended.Therefore,the quality control of the entire process of water-stable layer roadbed construction is particularly important.Through the performance test of cement stabilized crushed stone,the influence of material particle size gradation,cement dosage,curing age,curing temperature and other factors on the strength,drying shrinkage and temperature shrinkage of cement stabilized crushed stone are analyzed.The study on the compressive performance,frost resistance,drying shrinkage performance and temperature shrinkage performance of 4 grades of cement stabilized crushed stone materials shows that the more fine aggregate content,the worse the frost resistance of the material,the greater the drying shrinkage,and the temperature shrinkage resistance.The worse;when the critical particle size ratio RC(Ratio of critical particle size)is 50%～62%,its size is positively related to the long-term strength of cement stabilized crushed stone;the unconfined compressive strength of the mixture varies with the cement dosage When the cement dosage is less than 10%,the strength will increase by about 2.0MPa for every 1% increase in the cement dosage.Within the curing temperature range of 20℃,the increase in material strength is due to the increase in the curing temperature;The specimens with low cement content(3%,4%)aggregate 7d curing age can meet the basic strength of the mixture at a curing temperature of 10℃.Calculate the force of the roller on the roller compacted layer based on the nodal load application method;use a vibrating wire sensor to study the dynamic response of the roller compacted layer to different depths under different rolling passes.In the test,after the third pass of strong vibration,compaction No longer increases,the strain of No.3 and No.4sensors decreases,and the settlement “bounces up” in the fifth pass of strong vibration,the earth pressure and strain decrease,and the surface part of the roller compacted layer is vibrated loosened,indicating that the LSV220 single The steel-wheel full-hydraulic dual-drive vertical vibratory roller adopts the rolling combination mode of "one static pressure,one weak vibration,three strong vibration,and one static pressure" in the rolling construction of a water-stable layer,which can effectively improve the rolling quality;In the strong transparent tempered glass,a rolling action line is observed at about 53 cm from the surface,indicating that the water-stable compaction effect is better within the range of 53 cm,and the thickness of the loose paving should not exceed 53 cm.Relying on the construction project of the construction material transportation channel Rongcheng to Yixian in Xiong’an New District,the GNSS(Global Navigation Satellite System)positioning system is used to monitor the construction position,compaction trajectory,number of compaction passes,and travel speed of the roller in real time;The moisture content measurement of the mixing station and the test section found that the coefficient of variation of the moisture content of the mixture in the mixing station is smaller than that of the on-site mixture.The greater the coefficient of variation of the moisture content of the rolled material in the test section,the smaller the average value of compaction.The coefficient of determination of the coefficient of variation of moisture content on the degree of compaction is R2=0.9413.When the coefficient of variation of moisture content is controlled below 9%,the standard value of compaction can reach 98%.The tangency and intersection relationship of the circle measured by the compactness sensor is used to study the influence of the measurement method on the measurement accuracy.It shows that the measurement effect is better when the five circles intersect,and the compaction test is performed on 12 points of the two cross-sections.The difference in sand method detection does not exceed 0.6%.