A Water-Heat-Force Coupled Framework for the Preparation of Soils for Application in Frozen Soil Model Test

The freezing of soil containing a liquid is a complex transient heat conduction problem involving phase change and release or absorption of latent heat.Existing efforts have essentially focused on theoretical research and numerical simulations.In the present study,the problem is approached from an experimental point of view using the so-called“freezing model test”method.In particular,in order to establish a precise relationship between the model and the prototype,a temperature similarity criterion is derived using the condition of an equal number of Kosovitch.Similarity is also established with respect to other aspects.A similarity criterion for the water field is determined on the basis of relevant partial differential equations.Analogous criteria for the stress field and load are derived using an elastic model.The validity of this approach is experimentally verified.The research results provide a practical and reasonable method for calculating the parameters for preparing model soils.They also constitute a theoretical basis and a technical support for the design and implementation of a water-heat-force similarity coupled framework.

Weak Expansive Soil Physical Properties Modification by Means of a Cement-Jute Fiber

Sixteen groups of comprehensive tests have been conducted to investigate the modifications in the physical properties of a weak expansive soil due to the addition of a cement jute fiber.The tests have been conducted to analyze the liquid plastic limit,the particle distribution and the free expansion rate.The results show that:(1)With an increase in the cement-jute fiber content,the free expansion rate of the modified expansive soil gradually decreases,however,such a rate rebounds when the fiber content exceeds 0.5%and the cement content exceeds 6%.(2)With an increase in the cement percentage,the particle unevenness coefficient(Cu)and curvature coefficient(Cc)of the modified expansive soil tend to grow gradually.The Cc coefficient reaches 1.0 when the cement content is 6%.The unevenness coefficient of 16 soil samples is greater than 5.0,however,the Cu coefficient decreases when the cement content reaches 6%.(3)The plastic limit of soil increases as the cement content is made higher,while the liquid limit and plastic index decrease gradually.When the content of the modified material is 2%+0.1%~2%+0.7%(Cement content+jute fiber content),the change of particle size distribution is most obvious.(4)When the contents of cement and jute fiber are is 6%and 0.5%,respectively,the modification induced in the physical properties of soil samples corresponds to the best case.

A New Model for the Characterization of Frozen Soil and Related Latent Heat Effects for the Improvement of Ground Freezing Techniques and Its Experimental Verification

The correct determination of thermal parameters,such as thermal conductivity and specific heat of soil during freezing,is the most important and basic problem for the construction of an appropriate freezing method.In this study,a calculation model of three stages of soil temperature was established.At the unfrozen and frozen stages,the specific temperatures of dry soil,water,and ice are known.According to the principle of superposition,a calculation model of unfrozen and frozen soils can be established.Informed by a laboratory experiment,the latent heat of the adjacent zone was calculated for the freezing stage based on different water contents in the temperature section.Both the latent and specific heat of water,ice,and particles were calculated via superposition of the weight percentage content.A calculation model of the specific heat of the freezing stage was built,which provides both guidance and theoretical basis for the calculation of the specific heat of frozen soil.