A method for indoor damage evaluation of cement-improved sand roller compaction under dynamic load

Abstract

The invention provides an indoor damage evaluation method under the action of a cement improved sand rolling load. The indoor damage evaluation method comprises the following steps: confirming a cement content for a sand sample to be improved according to project requirements, acquiring the maximum dry density, the optimal water content and expected compression density of cement improved sand according to compacting experiments, taking a test sample, and performing static strength testing; performing dynamic load testing according to rolling loads, observing the development trend of an axial accumulation plastic strain of the test sample along with vibration times, and performing static shearing on an undamaged test sample; finally according to the deformation development trend of the testsample, and the loss rates of the static shearing strength of the test sample before and after the action of a dynamic load, evaluating the damage degree of the cement improved sand. By adopting themethod, a dynamic rolling load of a road roller is applied to the test sample, the static rolling load can represent a stress state of cement improved sand roadbed packing on a construction site in the layered rolling process, the damage degree of the cement improved sand is evaluated through double indexes, namely deformation and strength of the test sample, the evaluation principles are scientific, test instructions are common instruments, extra processing transformation is avoided, and the test cost is low.

Description

technical field [0001] The invention relates to a damage evaluation method for road subgrade filler, in particular to an indoor damage evaluation method under the dynamic load of cement-improved sand rolling. Background technique [0002] At present, there is no damage evaluation method specifically for cement-modified sand, and most of the existing technologies are proposed for the damage of concrete. The concrete damage evaluation method has certain reference significance for the damage evaluation of cement-modified sand. At present, many concrete damage evaluation methods have been used, such as acoustic emission, distributed optical fiber testing technology, 3D laser scanning technology, graphene technology, etc. Although there are successful cases, when they are applied to the damage evaluation of cement improved sand, there are certain problems. limitations. [0003] Although acoustic emission technology can respond to changes in the microstructure of materials in rea...

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Problems solved by technology

[0003] Although acoustic emission technology can respond to changes in the microstructure of materials in real time, it is a non-destructive testing method, but it is difficult to establish the relationship between mechanical parameters and acoustic emission parameters, and the acquisition of acoustic emission parameters is closely related to instrument performance, human operation, and materials. (see Zhang Wei. Application Research of Acoustic Emission Technology for Concrete Damage Detection, Doctoral Dissertation of Dalian Maritime University, 2012)

The distributed optical fiber test technology couples the deformation of the concrete with the strain sensing optical cable buried in the concrete, and then reverses the deformation of the concrete through its own deformation. However, when the cement-modified sand is rolled on site, the sand particles are in a state of large deformation, and the strain sensing It is difficult for the optical cable to be consistent with the deformation of the sand particles, and there is no steel bar in the concrete in the cement-improved sand, so the sensing optical cable cannot be fixed

3D laser scanning technology can only detect microscopic defects on the surface of the sample, and the defects inside the sample cannot be identified

The current damage evaluation methods are to establish the correlation between the detection parameters and the damage degree, and then obtain the damage degree indirectly through the obtained detection parameters. The human factors and the properties of the testing materials are different, so the reliability of the test results is difficult to guarantee