Study On The Impact Of Compacting Effect On Settlement Of Composite Subgrade For High Speed Railway

Chinese and foreign scholars did not attach adequate importance to the impact of compacting effect regarding theoretical studies on control of composite subgrade settlement. Since some designers develop conservative design based on existing experience, soft ground treatment design is accompanied by more or less waste or deficiency. This paper takes the study on the change rule of composite subgrade settlement under compacting effect through theoretical analysis and field test in response to the composite subgrade design theories extensively employed for high speed railway and the issues encountered during construction.Firstly, this paper probes into the present status and deficiencies of domestic and foreign studies on the influence of compacting effect on composite subgrade settlement of high speed railway, and investigates the working mechanism of the impact of compacting effect on composite subgrade settlement of high speed railway from the perspective of composite subgrade settlement computation theory.Secondly, this paper analyzes the stress and strain fields of compacting effect based on the mechanical model developed, thereby deriving related equations. In addition, study is taken on its change rule based on relevant cases. With some relevant cases, the change law of composite subgrade strain and stress field is studied along with the variation of parameters of pile-forming length, solid condition, the diameter of pre-driven borehole, expansionary force and so on.Thirdly, make analysis of the change rule of soil parameters between piles under compacting effect and the control parameters of composite subgrade settlement, and focus on the impact of compacting effect on skin friction of pile, composite modulus, effective pile length, and pile-soil stress ratio of composite subgrade and the change rule.Fourthly, derive the computing equation for composite subgrade settlement under compacting effect based on traditional computing method for composite subgrade of high speed railway in accordance with the change rule of relevant parameters of composite subgrade. Probe further into the impact of compacting effect on settlement of reinforced area and underlying bed. And analyse the result with which rules out the impact of compacting.Finally, tests and observations are carried out to determine the parameters of soil between piles as well as the change rules of settlement at different subgrade sections under compacting effect based on field conditions of Yangling Station of Xi’an-Baoji Dedicated Passenger Line; the change rule revealed is compared with the result obtained with settlement computing equation derived under compacting effect so as to verify the accuracy of computation theory..To sum up, this paper incorporates a relatively comprehensive study on the rule of impact of compacting effect on settlement change of composite subgrade of high speed railway, and provides reliable theoretical and technical support for relevant composite subgrade parameters and settlement computation under compacting effect, having enriched and perfected the analysis theories and techniques for composite subgrade of high speed railway.