Research Of Test Methods, Acceptance Criteria And Evaluation System For Compaction Quality Of Highspeed Railway Subgrade

Compaction quality of the embankment is a crucial link to ensure its engineering performance and long-term stability as well as reduce the post-construction settlement. Besides proper selection of soil and control of the construction, some influence factors (e.g. compaction quality, inspection and evaluation) are important measurements to guarantee the embankment quality required for a high quality embankment, especially for high-speed railway subgrade.Although there are requirements in specifications for the test methods, acceptance criteria and evaluation system of the compaction quality, there are still difficulties to control the compaction quality of subgrade due to the inhomogeneity of filling material and the limitations of test and evaluation methods. These kinds of disadvantages which may further influence the riding performance as well as reduce the service life of the road and then will result in great economic loss. As a matter of fact, in order to guarantee the compaction quality, many inspect methods were employed in high-speed railway construction in China to guarantee the compaction quality, which may delay the construction process schedule and are not adaptable to the requirement of modern construction including the compaction quality controlling of subgrade. These disadvantages are more evident when the coarse filling material is used in practice.It is a novel task, home and abroad, to study on high-speed railway subgrade to obtain the rapid and reasonable inspects method, rational control indexes and evaluation method with respect to compaction. Based on the practice of high-speed railway construction in China, this dissertation made an improvement and development in the test methods, acceptance criteria and evaluation system through theoretical analysis and field test. The innovational research achievements are summarized as follows:(1) According to deep analysis of laboratory and field test of compaction experiment with respect to two classical types of filling materials (e.g. completely decomposed sandy conglomerate and modified gravel) at Yueyang section of Wu-Guang High-speed railway as well as based on the comparison between China and Germany in terms of test measurement of compaction quality and controlling index, the correlation of the compaction degree applied in China and Germany was established. In order to adapt the development that the large-particle filling material is increasingly popular to be used in filling subgrade of hing-speed railway, a significant advice was presented that large scale compaction device should be added and applied in laboratory experiment to reflect the real engineering characteristics of large-particle filling material. Further, on the basis of the limitation of controlling index of porosity in current specification which cannot be efficient to control the compaction quality of subgrade, we presented another controlling index of compaction degree to control the compaction quality to satisfy the requirement of compaction required by subgrade of passenger dedicated line. This controlling index has been applied successfully in the practice of subgrade compaction engineering of Wu-Guang high-speed railway, and it will be included in the specification, Moreover, we obtained the correlation of K30 and Ev2, and presented another significant suggestion that we can simply select either K30 or Ev2 to weigh the compaction quality of subgrade, which can simplify the test procedures.(2) According to the different mechanical properties of subgrade in obvious compaction stages, the simplified roll-embankment integrated dynamic model to simulate the condition of subgrade compaction was presented. Based on the calculation of this model, we obtained the dynamic response of subgrade with obvious stiffness; also the correlation between dynamic response and stiffness of subgrade was obtained. Then, the method to monitor the compaction process dynamically was presented.(3) Based on the field experiment at Ha-Da high-speed railway and Xian-Pu railway, the roll-integrated compaction measurements and conventional measurements were conducted. Then, the relationship between CMV with respect to Roll-integrated compaction measurement and K30 was established in terms of comparison results between different detection measurements.(4) On the basis of numerous data of roll-integrated compaction measurements, the distribution of subgrade-compaction degree was obtained after analyzing the detection data statistically. Then, the main influence factors were analyzed. Further, the conception to evaluate the uniformity of compaction and the thought to control the non-uniformity of settlement were presented.