黄土路基大吨位压实参数研究

Study on Large Tonnage Compaction Parameters of Loess Subgrade

为解决大吨位压路机碾压黄土路基时合理压实参数选择的难题,以提高黄土路基的压实效果和施工经济性,利用"黄土—振动压路机"振动系统模型,分析了系统的振动响应,确定了振动压路机碾压黄土时的振动规律,即振动压路机初期宜用低频高振幅,后期宜用高频低振幅压实路基。通过利用YZ32D2型自行式振动压路机进行不同频率现场振动碾压试验及不同松铺厚度下最佳碾压遍数试验,对大吨位压路机压实参数进行了研究分析,提出了黄土路基压实过程中的最佳碾压频率和不同松铺厚度下的最佳碾压遍数,现场试验表明:大吨位压路机碾压黄土路基时,前期使用低频25 Hz碾压4遍,即可达到93%压实度,后期采用高频30 Hz进行振动碾压效果最佳;振动碾压遍数达到4遍之前,不同松铺厚度条件下压实度随碾压遍数增加而增大,超过4遍后,松铺30 cm对应的压实度达到峰值后有所降低并趋于稳定,松铺40 cm对应的压实度随碾压遍数的增加提升幅度逐渐降低,松铺50 cm相比松铺60 cm时压实度增加较快,而松铺厚度达到70 cm时,压实度随碾压遍数的增加提高趋势趋于缓和,很难达到施工要求的93%压实度。为避免因松铺厚度过大碾压遍数过多而消耗时间、增加机械台班数,建议每层松铺厚度不宜超过50 cm。此外,本研究给出不同松铺厚度时达到所需施工要求的振动碾压遍数推荐值及黄土路基大吨位压实工艺控制参数。

In order to solve the problem of reasonable compaction parameter selection for large tonnage roller compacting loess subgrade,and to improve compaction effect and constructional economy of loess subgrade, the "loess-vibratory roller"vibration system model is adopted to analyze the vibration response of the system. The vibration rule when vibratory roller is used in soil compacting is determined,i.e.,the initial use of low- frequency high-amplitude,~and later use of high-frequency low-amplitude for compacting subgrade.By using the YZ32D2self-propelled vibratory roller to carry out field tests with different frequencies and the optimum rolling times with different thicknesses,the compaction parameters for large tonnage roller are studied,and the optimal rolling frequency and the optimal rolling times with different loose thicknesses of loess subgrade are proposed.The field test indicates that (1)When using large tonnage roller to compact loess subgrade, low-frequency 25Hz should be used in the first 4rolling attempts to achieve 93%compaction degree or more.To reach the best effect,30Hz should be used later on.(2)Before reaching the 4th rolling attempt,the compaction degree increased along with the increasing number of rolling attempts under different loose paving thicknesses.When the rolling attempts set beyond the 4th attempt,the compaction degree corresponding to 30cm loose paving thickness decreased and tended to be stable after reaching peak value; the increase value of the compaction degree corresponding to 40cm loose paving thickness gradually decreased with the increase of the rolling number,at 50cm loose paving thickness,the compaction degree increased faster than that at 60cm,while at 70cm loose paving thickness,the increase value of compaction degree tended to be alleviated with the increasing number rolling attempts,which is difficult to meet the 93% compaction requirement in construction.To avoid exceeding amount of time wasted and too machines required due to the excessive loose paving thickness,it is recommended that the loose paving thickness of each layer should not exceed 50cm.Besides,the irecommended number of vibrating rolling attempts necessary to meet the construction requirements and the control parameters of the compaction process of large tonnage comnaction on loess subgrade with different loose paving thicknesses are provided.