Prediction method for long-term deformation of freeze-thaw damaged soft rock

Abstract

The invention discloses a prediction method for long-term deformation of freeze-thaw damaged soft rock, provides a dangerous rock body deformation judgment criterion for geotechnical engineering construction in a cold region, and guarantees the safety of foundation engineering in whole life cycle use. The method comprises the following steps: (1) constructing a freeze-thaw aging damage variable multivariate function; (2) constructing a freeze-thaw aging damage coupling creep mechanics constitutive equation in combination with a freeze-thaw aging damage variable multivariate function; (3) performing standard regulation sampling on the on-site soft rock, and recording the change value of the strain of the rock sample along with the stress and time; (4) carrying out nonlinear fitting on the strain time curve and the constitutive equation to determine each mechanical parameter in the equation; (5), converting the rock mechanics parameters into rock mechanics parameters; (6) determining equivalent freeze-thaw cycle times through an indoor and outdoor freeze-thaw cycle equivalent equation; (7) actually measuring the spatial distribution rule and displacement increment of a rock mass stress field on site; and (8) predicting a strain value corresponding to the rock mass at a future tf moment.

Description

[0001] The invention relates to the field of engineering technology, in particular to a method for predicting long-term deformation of freeze-thaw damaged soft rock. technical field [0002] A method for predicting long-term deformation of freeze-thaw damaged soft rock mass. Background technique [0003] Soft rock refers to the rock mass with obvious plastic deformation characteristics under certain conditions, mainly mudstone, shale and siltstone, etc., and its main characteristics are low strength, large porosity, poor particle cementation, significant weathering, and joints. The surface is developed and contains a large amount of expanded clay minerals, which occur in large quantities in the form of sedimentary rocks, igneous rocks or metamorphic rocks on the crustal surface. The special properties of soft rock make it more sensitive to external influences than hard rock. As far as my country's infrastructure construction in the western region is concerned, it faces a lar...

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Problems solved by technology

[0004] In recent years, scholars at home and abroad have conducted many studies on the deformation and degradation mechanism of freeze-thaw soft rock in cold regions at the experimental level and damage theory, but the criteria and methods used in actual cold region engineering are few and incomplete, and most of them are limited to the consideration of freezing and thawing. Transient mechanical behavior of soft rock after melting, but in reality, soft rock undergoes long-term deformation to failure under the action of external loads is more common; at the same time, there are few methods for constructing soft rock macro damage mechanics constitutive models, and most For example, the application number 201510387574.3 "A Method for Establishing a Soft Rock Creep Constitutive Model Applicable to the Whole Process of Loading and Unloading" builds a constitutive model describing the rheological characteristics of soft rock by introducing Kelvin bodies and spring elements , the model can quantitatively analyze the constitutive relationship of soft rock attenuation creep and residual deformation after unloading. Under certain conditions, the model has limitations. Based on this, while considering the rheological aging damage and introducing external damage factors (such as freeze-thaw damage), the long-term deformation of rock is a comprehensive reflection of the coupling condition of freeze-thaw aging damage, and the model The parameters are converted into mechanical parameters of rock mass to make it closer to the deformation characteristics of the damaged rock mass on site, which is more reliable as a deformation prediction index

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