Method for evaluating disturbance degree of undisturbed hollow cylindrical sample of residual soil

Abstract

The invention discloses a method for evaluating the disturbance degree of an undisturbed hollow cylindrical sample of residual soil. The method comprises the following steps: A, taking a blocky sample and calculating the void ratio of an in-situ state soil sample; b, preparing an undisturbed hollow cylinder sample and loading the sample: cutting the undisturbed hollow cylinder sample, sleeving the sample with a rubber membrane, and mounting the sample on a hollow cylinder torsional shear apparatus; c, sample saturation: simultaneously increasing the inner confining pressure, the outer confining pressure and the back pressure from zero; d, sample consolidation: keeping the back pressure at 500kPa, gradually increasing the inner confining pressure and the outer confining pressure from 520kPa, and completing consolidation; e, calculating a disturbance index DI according to the drainage volume delta V, the sample size and the in-situ state soil sample void ratio in the consolidation process; f, evaluating the disturbance degree of the sample: evaluating the disturbance degree of the sample according to the DI value; g, sample shearing, unloading and instrument cleaning, wherein after evaluation is completed, the sample is the sample with small disturbance or extremely small disturbance. The method is easy to implement, simple and convenient to operate, low in test cost, high in test precision and high in evaluation efficiency.

Description

technical field [0001] The invention relates to the field of hollow torsional shear tests in geotechnical tests, in particular to an evaluation method for the disturbance degree of the original hollow cylindrical sample of residual soil, and is also applicable to the disturbance of samples in tests such as triaxial shearing and direct shearing in geotechnical tests degree evaluation. Background technique [0002] Geotechnical materials such as residual soil widely exist in nature. According to the research, this kind of special rock and soil materials generally have obvious anisotropy (K.Onitsuka, S.Yoshitake, M.Nanri. -30), to a certain extent, it has brought difficulties to scientific research and engineering construction. At present, the research method for the anisotropy of geotechnical materials is usually the hollow torsional shear test, which requires the preparation of thin-walled hollow cylindrical soil samples, and this process inevitably disturbs the soil sample...

AI Technical Summary

Problems solved by technology

[0004] (1) For the measurement of on-site or indoor shear wave velocity, additional equipment needs to be purchased, which greatly increases the test cost

At the same time, the on-site test has difficulties such as complicated operation and inconvenient carrying of the instrument.

[0005] (2) If the natural soil, especially the residual soil, has significant variability, the results of the wave velocity measured on site are often relatively discrete, making it impossible to accurately evaluate the degree of disturbance of the sample

[0006] (3) The indoor wave velocity measurement test did not restore the stress state in situ

[0007] (4) Due to the cumbersome installation steps and complicated operation of the hollow torsional shear test sample, there may be some disturbance to the sample during the sample loading process

So far, no scholars have proposed a reasonable evaluation method and index

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