A method for measuring the volume of a soil sample by a dry-wet cycle test and a sample volume change test disc

Abstract

The invention provides a method for determining the volume of a soil sample by a dry-wet cyclic test. N groups of XY right-angle coordinate systems are uniformly arranged on a water permeable stone along the direction of diameter, wherein N is more than or equal to 1; the N groups of XY right-angle coordinate systems share one original point, and the original point is overlapped with a circle center O of the water permeable stone; an annular cutter which is internally provided with a soil sample is arranged on the surface with scales of the water permeable stone; and four crossed points are formed by the soil sample and the XY right-angle coordinate systems, scale values Xij, Xij', Yij and Yij' corresponding to the four crossed points are recorded, and according to the scale values, the bottom area Sj of the soil sample is calculated, the height hj of the soil sample is determined and the volume Vj=hj*Sj of the soil sample is calculated. The invention further correspondingly provides a test sample body variable testing disc used for the method. The method provided by the invention is simple to operate and can guarantee the consistency of measuring points, and a determination result is relatively close to a real volume of the soil sample; and the test sample body variable testing disc is simple in structure and low in manufacturing cost.

Description

technical field [0001] The invention relates to a method and a device for measuring the volume change of a sample of unsaturated soil under the change of water content, and belongs to the technical field of geotechnical testing. Background technique [0002] The soil with a certain water content is easily deformed after being subjected to external force, so that its structure changes. In the process of soil from saturated state to unsaturated soil state, the water content gradually decreases, the matrix suction increases, and the sample volume gradually decreases. See "Indirect Estimation of Volume Water Content in Pressure Plate Test Using Shrinkage Test Data" ( Zhang Hua et al., "Rock and Soil Mechanics", Volume 20, Issue 2). In the process of testing from saturated soil to unsaturated soil, the water content of the sample is usually measured by a balance, and the measurement of the volume change of the sample has always been a problem that is difficult to solve. [0003...

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Problems solved by technology

However, in most cases, the sample cannot be in the state of rubber film sealing, so this method has certain limitations

The third method is to use the vernier caliper to pass the measurement data at different points of the sample and average them, so as to obtain the average height and average diameter of the sample, and finally obtain the volume of the sample. , is convenient and easy to operate, and the operation is simple, but when there is a small change in the sample volume but cannot be ignored, this method has certain defects, see "Measurement of the Shrinkage Characteristic Curve of the Surface Soil of Earthen Building Sites" (Liu Ping, "Rock Journal of Soil Mechanics and Engineering, Volume 29, Issue 4)

Since the same point of the sample is not tested in the measurement, it cannot really reflect the real change of the height and diameter of the soil sample

[0004] Especially in the dry-wet cycle test of soil samples, the height and diameter of the sample will change slightly with the evaporation of water content of the soil sample. When using a vernier caliper to measure, each measurement needs to be aimed at the same measurement point, but It is difficult to test according to this principle in practice

For example: soil samples with a certain water content usually show plasticity, so when marking the measurement points of the soil samples, the marked points of the soil samples will be deformed, so it is not feasible to mark and measure; usually, the soil samples will be moved during the measurement process , so that the cycle measurement points before and after the soil sample are inconsistent, so the change of height or radius is not the data change of the same measurement point, and it is difficult to reflect the real change of the soil sample change. Therefore, the measurement of the volume change of the soil sample in the drying and wetting cycle of the soil sample cannot reflect real law of change

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