Amount Of Frost Heave Research Articles

Effects of salt concentration on strength and creep behavior of artificially frozen soils

The effects of salt concentration on strength and creep behavior of artificially frozen soils are investigated experimentally. In recent years, considerable interest has developed concerning underground or inground storage of cryogenic liquids. If an LNG storage tank is constructed in the ground with no heating equipment around the tank, the ground will become frozen over the years. To examine the safety of the LNG inground storage tanks, it is necessary to estimate the amount of frost heave involved in such freezing of ground and the frozen-earth pressure acting on the wall of the tank. In this study, the mechanical properties of frozen soils are determined experimentally. These properties are required to analyze the above problems by the finite-element method. Since LNG inground storage tanks are often constructed along the coast, tests were made on frozen soils containing salt.

Heaving conditions by freezing of soils

The engineer is normally concerned with the effects of the freezing of soils; the heaving pressure, the amount of frost heave and the thaw weakening. To quantify these effects various soil parameters and theoretical considerations are used, often leading to different frost susceptibility criteria. Although a tremendous amount of work has been done to develop frost susceptibility criteria, it seems that, from an engineering point of view, little progress has been made over the last decades. However, an important development has taken place concerning the theory behind the frost heaving mechanism and to develop numerical models of frost heave.

Frost heave in an instrumented soil column

Thermocouples, electrical resistivity gages and tensiometers were installed at various depths in a column of Fairbanks silt 100 cm long and about 14 cm in diameter. The water level was maintained at a depth of 45 cm below the surface and the volume of water taken up during the freezing process was monitored. Three freezing tests were conducted, two with a surcharge equivalent to about 35 cm of water pressure and one with a surcharge equivalent to about 350 cm of water. The upper 15 cm of soil was frozen at a rate of about 1 cm/day. The soil moisture tension increased (became more negative) throughout the length of the sample when the first ice was nucleated. All three samples exhibited a similar behavior. The amount of frost heave at the end of the tests was 6.0 and 2.1 cm for the two samples with the small surcharge and 3.2 cm for the sample with the higher surcharge. During freezing the two samples with the small surcharge took up 615 and 410 cm 3 of water while the sample with the larger surcharge took up 490 cm 3 of water.

Design of tunnel support systems using ground freezing

One of the more promising techniques in soft ground tunneling through urbanized areas is the use of artificially frozen ground for temporary tunnel support. This paper describes the general design considerations involved in the ground freezing method. Various factors are discussed which influence the selection of the freezing temperature, the thickness of the frozen zones and the spacing of the freeze pipes. The time required to achieve freezing is discussed in addition to the amount and rate of frost heave caused by the freezing. To illustrate the applicability of the freezing method, various considerations in the design of an 8-ft. diameter tunnel in upstate New York, a 75-ft. diameter tunnel in Georgia, and a 12 1/2-ft. diameter tunnel in Washington, D.C. are discussed. All three of the tunnels were to pass immediately beneath mainline railroad tracks. A laboratory testing program was implemented to determine the effects of the repetitive train loads on the zone of frozen soil around the tunnel perimeter. Stress-controlled repeated load triaxial tests were performed on both undisturbed and remolded samples frozen from temperatures of −7°C for the New York tunnel to −10°C for the Atlanta and Washington tunnels. Static testing consisted of both quick triaxial tests and creep tests on frozen samples of the various soil types. It was found that there was little difference between the cumulative strain response from repeated load tests and static tests for the low frequencies investigated (one-quarter to one-half cycles per minute). Hyperbolic stress—strain functions were developed to simulate the stress—strain relationship for various cumulative loading times. The stresses and strains in the frozen soil tunnel configuration were computed by the finite element method, using both linear and hyperbolic stress—strain functions. Tangent modulus values were varied to reflect the decreasing modulus with increasing loading time. The analyses indicated that zones of frozen soil of approximately 3 ft. thick were required for both the New York and Washington tunnels. However, high tensile stresses were calculated for the Atlanta tunnel, precluding the use of the freezing method.

Frost Heaving in Alfalfa Establishment on Soils with different Drainage Characteristics1

AbstractThe susceptibility of alfalfa (Medicago sativa L.) to frost heaving is a major problem in stand establishment in southern Illinois. This study was conducted at Carbondale, Illinois, to determine the effects of frost heaving on the establishment and production of alfalfa cultivars in relation to soil drainage characteristics. Four alfalfa cultivars (‘Cody’, ‘Spredor’, ‘Weevlchek’, and ‘WL‐307’) were seeded on three soil series, a deep well‐drained AIford (Typic Hapluadalf, fine‐silty mixed mesic), a moderately well‐drained Hosmer (Typic Fragiudalf, fine‐silty, mixed, mesic) with a fragipan starting at a depth of 60 to 70 cm, and a nearly level poorly‐drained Weir (Typic Ochraqualf, fine, montmorillonitic, mesic). Piezometers were installed in each soil to monitor the presence of perched water tables and their position to the soil surface. Small wooden dowels were used to assess soil movement in relation to alfalfa seedling heave. The higher amount of heaving as measured by the distance wooden dowels were raised above a reference point occurred when the night temperature was a few degrees below freezing and the day temperature was above freezing, with a perched water table near the soil surface. Poorly‐drained, Weir soil had the highest perched water table, most alfalfa seedling heave, greatest alfalfa seedling winterkill, and most dowel heave. In contrast, well‐drained Alford series had no perched water table, no appreciable seedling heave or winterkill, and least dowel heave. No significant differences in amount of frost heaving of seedlings were noted amonga alfalfa cultivars on any drainage site. Highest dry matter yields were obtained on the well‐drained Alford site; significant yield reductions occurred as soil drainage class became more poorly drained. Alfalfa stands were successfully established on the well‐drained Alford series and the moderately well‐drained Hosmer series. Soil drainage characteristics did influence alfalfa establishment and production in the climatic transitional zone of the central U. S. Poorly‐drained soils should not be considered for alfalfa production.

Pore Water Pressure and Consolidation in Unfrozen Soil near the Freezing Front

When the soft soil freezes accompanying with the water suction, the effective stress increases with the lowering of pore water pressure that takes place near the freezing front, and thereby the unfrozen soil adjacent to it is subjected to a fairly strong dewatering consolidation. In this paper pore water pressure distribution in front of unidirectional freezing front penetrating at a constant rate is analyzed theoretically, and it is found that the lowering of pore water pressure is larger than expected. Therefore the lowering of the pressure may explain a soft soil subsidence after thawing and sludge dewatering by freezing. Influence region of dewatering consolidation, δs, is given by Cυ/U, and transitional time attaining to a steady state, τt, is given by A·Cυ/U2. Here Cυ is coefficient of consolidation, U is frost penetration rate and A is a positive constant.In the case of soil which is relatively low in the degree of consolidation, the freezing expansion and dewatering consolidation take place simultaneously, and at far from δs in unfrozen soil the result of their mutually subtracted effect is observed as the amount of frost heave. Then, frost heave ratio, ξ, is given approximately by ξ0+nfΓ. Here ξ0is a characteristic constant of the soil, nf is free water content of soil at freezing temperature andΓ is nondimensional volumetric expansion ratio of water at freezing ≅ 0. 09.

An Experimental study of the Effect of Loads on Frost Heaving and Soil Moisture Migration

The application of the artificial freezing of soil to civil engineering has been developed and well utilized in Japan since 1962. The application, however, involves some difficult problems in spite of its benefits. Part of them has been solved on the practical as well as theoretical base mainly by the present authors. One of the most significant problems which remain unsolved, is the frost heave problem. The present paper discusses the problem under various conditions of load pressure in the open system.Undisturbed soil sample, 10 cm in both diameter and height was enclosed in an acrylic acid resin cylinder of the apparatus (Fig. 1). The lower part of the cylinder contains an end cup filled with water. The surface of the water in the end cup was made to contact the bottom of the soil sample through the porous plate. The soil sample was sufficiently precooled at 0°C, and then cooled from the upper side at -2.5°C. The water in the end cup was kept at 0 °C during the freezing.The following results were obtained : 1. The soil system discharges water during freezing when the load pressure exceeds a certain value (Fig. 3, 4).2. The amount of frost heave decreases in accordance with the increase of load pressure (Fig. 7). The relation between the heave ratio (h), which means the ratio of the maximum heave amount to the initial height of sample, and the load pressure (p) is approximated as follows; h= h0+ c/p, where h0 and c are constants.It is understood from this equation that complete elimination of heave action will be difficult, because it is assumed that h0 is due to freeze-expansion of adsorbed water around soil particles behind the freezing front. 3. The relation between the amount of heave (Vh) and the amount of migrated water (Vw) is expressed by the following equation; Vh= (1-α) ΓVwo± (1 +Γ) Vw where, Γ is the coefficient of volume expansion of water changing into ice, Vwo is the volume of water in soil before freezing and a is a constant (0<α<1). Therefore, when soil moisture is discharged from the soil system (Vw< 0), the frost heave decreases in amount. The value of α was calculated as 0.3-0.4 in the present experiment (Figs. 9-12).

Theoretical Studies of Ice Segregation in Soil

AbstractThe mathematical theory of heat conduction is applied to the analysis of ice segregation processes in soil. A diffusion equation is first employed for the flow of soil moisture. Two new quantities, the rate of ice segregation,σ and the segregation efficiency, E, are introduced. The first is the rate of ice growth measured as mass per area per time. The latter is defined as E = σL/(K1∂T1/∂x−K2∂T2/∂x), where L is the latent heat of fusion of ice, T1and K1are the temperature and thermal conductivity of frozen soil, and T2 and K2 are the temperature and thermal conductivity of unfrozen soil. Three types of soil freezing can be classified in terms of E: freezing of non-frost-susceptible soil (E = 0), perfect segregation (E = 1) and imperfect segregation (0 &lt; E &lt; 1). Finally, the mathematical boundary conditions at an advancing frost line are obtained in freezing, frost-susceptible soil (E ≠ 0). Two parameters related to the structure of soil are pointed out, which seem to be valid criteria of frost susceptibility. The amount of frost-heaving is derived under special conditions.

Theoretical Studies of Ice Segregation in Soil

Abstract The mathematical theory of heat conduction is applied to the analysis of ice segregation processes in soil. A diffusion equation is first employed for the flow of soil moisture. Two new quantities, the rate of ice segregation,σ and the segregation efficiency, E, are introduced. The first is the rate of ice growth measured as mass per area per time. The latter is defined as E = σL/(K 1 ∂T 1/∂x−K 2 ∂T 2/∂x), where L is the latent heat of fusion of ice, T 1and K 1are the temperature and thermal conductivity of frozen soil, and T 2 and K 2 are the temperature and thermal conductivity of unfrozen soil. Three types of soil freezing can be classified in terms of E: freezing of non-frost-susceptible soil (E = 0), perfect segregation (E = 1) and imperfect segregation (0 &amp;lt; E &amp;lt; 1). Finally, the mathematical boundary conditions at an advancing frost line are obtained in freezing, frost-susceptible soil (E ≠ 0). Two parameters related to the structure of soil are pointed out, which seem to be valid criteria of frost susceptibility. The amount of frost-heaving is derived under special conditions.