Artificial freezing theory and engineering application basis of thick and deep topsoil

It is mainly engaged in the basic research of artificial ground freezing theory and engineering application, such as shaft engineering in thick and deep topsoil, deep foundation pit and tunnel engineering. The Laboratory has conducted research in this field for more than 60 years. It has led and participated in solving China’s major theoretical and key technical problems in this field, making China’s artificial stratigraphic freezing theory and technology grow out of nothing. From general tracking to leading the frontier of the subject, the Laboratory has made a great contribution.

Main research contents are listed as follows.

(1) The thermal properties of deep soil and its relationship with buried depth, mineral composition, water content, formation temperature and gradient; the spatiotemporal evolution law of multi-circle non-uniform freezing temperature field; the relationship between the formation and development of freezing temperature field and soil property, water content, freezing circle diameter, freezing temperature, freezing depth, freezing process and boundary conditions, etc.

(2) Constitutive relationship of artificial frozen soil in thick and deep topsoil, strength properties of artificial frozen soil under excavation and unloading conditions; the relationship of the strength and creep property of non-uniform and non-constant frozen soil with the soil properties, water content, freezing temperature and distribution, load characteristics, etc.

(3) Based on multi-circle thick frozen wall, the constitutive relation, overall strength and structural stability, geometric effect, structural effect, constraint effect, heterogeneous effect and unloading effect of shaft excavation for frozen wall of artificial frozen soil are studied; to obtain a theoretical model to describe the integrity of frozen wall by using the mechanical properties of frozen soil specimens;

(4) The formation mechanism of ice segregation  induced by water migration in the soil freezing process and its relations with water (water content, hydrological properties), soil (mineral composition, gradation), temperature (temperature, temperature gradient), pressure (loading history, magnitude and variation of acting path) and other factors; to get the rule of frost heave and thaw of artificial frozen soil as well as the control mechanism and key techniques.