Method of testing strength of expansive soil by dry and wet expansion method and complete softening method

Abstract

The invention discloses a method of testing strength of expansive soil by a dry and wet expansion method and a complete softening method. The method comprises the steps of treating an expansive soil sample by the dry and wet expansion method and the complete softening method, obtaining corresponding shearing strength tau 1 and tau 2 by the action of different normal stresses, and taking an averageof tau 1 and tau 2, or tau 2 as the strength of the expansive soil under a normal stress condition. The strength of the expansive soil is tested by the two methods. For the dry and wet expansion method, an expansive soil body is not limited and is allowed to deform freely; the strength of the expansive soil after 2-3 dry and wet cycles is reduced to be stable basically; the workload is low; and atest period is shorter. For the complete softening method, a partially destabilized expansive soil side slope is inverted at the strength of far below several thousand Pa for testing and explanation.Compared with a single measurement method, the method is more precise with the adoption of the dry and wet expansion method and the complete softening method simultaneously.

Description

technical field [0001] The invention belongs to the field of expansive soil strength testing methods, and in particular relates to a method for testing the strength of expansive soil by combining a dry-wet expansion method and a complete softening method. Background technique [0002] Expansive soil is a special kind of high plasticity cohesive soil, which has the engineering characteristics of water absorption expansion and loss of water shrinkage. Expansive soils are sensitive to climate change, and soil slopes in expansive soil areas, such as embankments, road cuttings, channel slopes, etc., often produce instability and damage, which brings huge disasters to engineering construction. Investigations and studies have found that the strength of expansive soil exhibits obvious "fluctuation" characteristics, that is, the strength of expansive soil decays with time. It is precisely because of this variability that how to determine the strength of expansive soil has become a d...

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Problems solved by technology

[0003] At present, although the dry-wet cycle test method is mostly used in the determination of the strength of expansive soil, there are the following shortcomings in only using the dry-wet cycle test method: 1. The strength index derived from the inversion of some unstable expansive soil slopes is even as low as several kPa, far less than Its dry-wet cycle strength, only using the dry-wet cycle test is not enough to explain the above phenomenon; 2. The dry-wet cycle test lacks corresponding specifications, and there is no clear standard for the test control conditions such as the number of cycles, dehumidification temperature, etc., which will not only cause dispersion in the test results , some test conditions (such as 50 ℃, 70 ℃ dehumidification temperature) are also quite different from the actual engineering

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