Study On Filled Soil Classification And Compaction Standard Of Railway Subgrade

Subgrade structure, as the main structure of railway construction, should have enough carrying capacity and deformation resistance capacity, can stand repetitive strength of the vehicle load without structural destruction and excessive sedimentation and deformation, meanwhile, it should have preferable penetration resistance capacity and water stability, to reduce water immersion and intenerate effect, therefore maintaining long time stability of the subgrade.The soil characters and compactness of the filling soil have very obvious effects on subgrade engineering characteristics, therefore, countries around the world attach much importance to the study of subgrade filling soil classification as well as the compaction standard, and constituted relevant design code.Along with the rapid development of the railway construction in China and continuous improvement of the traveling speed, in the subgrade design and construction, the problems in the current subgrade code as to the filling soil classification and compaction standards are beginning to show up, thus adjustment to it is necessary, and the subgrade design standards which fit the situation of present day China should be compiled. Therefore this thesis made a study to the filling soil classification and compaction standards in combination with the implementation of the science and technology program of the Ministry of railway.It analyzed the characteristics and differences of railway engineering filling soil classification and rock and soil classification standards, made proposals to consolidate the two classification standards as well as the implementation approach; Starting with analysis of the strength, deformation, penetration, tamping of different filling soil, it discussed the "filling soil classification" and "filling soil grouping" in the existing railway subgrade design code and concluded that the basis on which the classification and grouping are made are too brief, and they can not reflect objectively the effects of the factors as content, granular diameter grading and fine granule ingredient on the soil characters, and proposed corresponding revision methods.It analyzed the physics mechanics bearing of the tamping indexes such as compaction coefficient K_h, roadbed coefficient K₃₀, air content n_a and their correlation. With analysis of the correlation of the mechanics indexes as the compactioncoefficient Kh of different filling soil and the compression modulus a^ CBR value, unconfined compression strength qu, K5 value, minisize penetration resistance Ps, it discussed the essential cause the compaction coefficient Kh which reflects the physics property index of the filling soil does not match the roadbed coefficient K? which reflects the mechanics property index of the filling soil, and put forward the value taking suggestions as to relevant subgrade compaction coefficient Kh according to the principles of deformation control.It analyzed the correlation of roadbed coefficient K:!o and deformation modulus value EV2, compaction coefficient Kh and CBR value and porosity n, and proposed control value of subgrade filling soil compaction index (Kh, K.!o> n) ; Based on the field dynamic test data and theoretical research results, it analyzed and calculated the strength and deformation of the subgrade, and proposed the revision scheme of the subgrade compaction standards taking into consideration of the design speed.