Mixed calorimetry based specific heat calculating method for frozen soil

Abstract

The invention provides a mixed calorimetry based specific heat calculating method for frozen soil. The method comprises the following steps: a soil sample with the mass of m is taken, and water content w of the soil sample is measured; the soil sample is placed in a freezer at the constant negative temperature t lower than 0 DEG C for 60 h, and the total heat Q0 of the frozen soil sample is acquired; the frozen soil sample is placed in the freezer for 60 h; the total heat Q1 and Q2 required by the soil sample at the constant negative temperature (t-delta t) and (t+ delta t) for being heated to heat exchange balance temperature t1 and t2 from initial temperature are calculated respectively; the heat Q3 and Q4 are determined by measuring specific heat and content of soil particles and water; the specific heat c of the frozen soil sample at the specific negative temperature t is obtained according to a formula. The method has the beneficial effects that the specific heat of the frozen soil sample at a certain temperature point can be calculated precisely, conventional errors caused by thermal calculation based on average specific heat are improved, the minimum error is 0.039 DEG C, the maximum error is 0.5955 DEG C, and actual engineering needs can be met. Predicted temperature of a temperature field in a freezing method construction process can be increased to a larger extent by aid of precision improvement, and the safety of freezing method construction is guaranteed.

Description

technical field [0001] The invention mainly relates to the field of frozen soil engineering, in particular to a method for calculating the specific heat of frozen soil based on a mixed calorimetry method, which is mainly used for measuring the specific heat capacity of natural frozen soil and artificial frozen soil. Background technique [0002] my country is the third largest permafrost country in the world, of which 53.5% is seasonally frozen and 21.5% is permafrost. The engineering problems often encountered in engineering buildings in seasonally frozen regions and permafrost regions are frost damage, which are mostly frost heaving or thawing caused by the growth or disappearance of ice in the soil. The frost heaving and thawing of the soil lead to the rapid destruction of the project, which not only affects the normal use of the building, but even threatens the safety of people's lives and property. In order to guide the construction of the project and ensure the safe a...

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Problems solved by technology

[0006] At present, when analyzing the freezing temperature field to calculate the specific heat, there are mainly the following problems: (1) the specific heat is assumed to be constant in the calculation of the temperature field in the freezing stage; (2) the specific heat of the soil before and after freezing Calculated separately, but does not consider the influence of phase change on it, ignoring the latent heat released during the phase change of water in soil

In view of the above problems, firstly, the fact that the specific heat of the soil changes during the freezing stage is undoubted; secondly, during the freezing stage, the phase transition of water in the soil is accompanied by a large amount of heat release, which will inevitably cause a change in the specific heat value. If the change of specific heat is ignored, it will inevitably cause a gap between the calculated cooling capacity and the actual cooling capacity, resulting in a waste of resources

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