| In recent years,with the rapid development of China's economy and the national policy guidance.A large number of high grade highways are rapidly built in the western region.Due to the complexity and uniqueness of topography and geomorphology in this area,the subgrade is usually built by the way of high fill embankment.In the central and western regions,the loess distributes widely and has a large thickness.So when the high fill embankment is built in this area,usually choose the local loess as a filler.Compared with other fillers,loess has the characteristics of developed pore,collapsibility and low strength.However,modern road transportation is characterized by high speed,high load,high efficiency,high income and flexibility.These characteristics put forward higher requirements on the quality of highway construction,especially on the compaction and post-construction settlement of high fill embankment with loess filler.In order to eliminate the defects of loess filler,ensure the strength and stability of subgrade-pavement,it is an effective measure to compact subgrade-pavement with high standard.However,using the traditional compaction methods to compact loess high fill embankment can't make the embankment compaction meet the design requirements.This is because of the urgent requirements of the construction period and its own technical limitations.Therefore,in order to improve the efficiency and quality of compaction,ensure the construction period,reduce post-construction settlement and eliminate the collapsibility of loess,a new comprehensive compaction method is introduced and it has important practical significance.Based on the high fill embankment with loess filler,Yanjiafeng road section of Taihang highway.A comprehensive compaction method for the combination of layered vibratory compaction and heavy tamping is proposed.Then evaluate the effect of the comprehensive compaction method through 3aspects:indoor compaction test,field construction evaluation,and post-construction settlement monitoring.(1)Firstly,make indoor compaction test for loess filler.Determine the average maximum dry density of this filed,=1.705g/cm~3.The optimum water content,=12.992%.Therefore,the control of water content is about13%when the field is compacted.(2)The high fill embankment is paved and compacted with comprehensive compaction method.Then evaluate the compaction quality according to the degree of compaction and porosity.The results show that,only making a layered vibratory compaction,the compaction effect is more uniform,which is about92%.However,it cannot meet the requirements of the standard.But after the heavy tamping,the compaction degree is further improved,the porosity is reduced,and the design requirements are fully met.Besides,the degree of compaction curve is periodically distributed as the compaction depth increases,and the period is 3m.(3)After indoor collapsibility test,it is shown that the embankment's coefficient of collapsibility cannot meet the requirement after only using the method of vibratory compaction.But the comprehensive collapsibility method can completely eliminate the collapsibility of loess filler.And the higher the compaction,the smaller the collapsibility.(4)After the construction is accomplished,a one-year in-situ monitoring test is conducted to monitor the post-construction settlement of embankment.The results show that the settlement of the embankment become stable about240 days after the compaction.And the post-construction settlement only account for about 0.1%of the filling height one year later,the compaction effect is remarkable.The shorter consolidation settlement time and the smaller post-construction settlement fully illustrates the advancement of the comprehensive compaction technology.In the total settlement,the settlement of the filling body account for about 90%of the total settlement,it shows that the post-construction settlement of high fill embankment is mainly the compression deformation of the embankment itself. |
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