CN-117030566-B - Device and method for measuring and testing unidirectional freeze-thawing permeability coefficients of soil bodies in different height ranges

Abstract

The invention provides a device and a method for measuring and testing unidirectional freeze thawing permeability coefficients of soil bodies in different height ranges, the device comprises a reservoir, a sample cylinder, a top cold plate structure, a bottom cold plate structure, a water supply pipe structure and a water varying head pipe, wherein the reservoir is positioned above the sample cylinder, overflow holes are arranged on the side surface of the reservoir and are used for controlling the water surface height of the reservoir, the sample tube comprises a plurality of soil sample unit tubes which are stacked up and down, the soil sample unit tubes are filled with soil samples to be measured, water injection holes are formed in the upper portion of each soil sample unit tube, drain holes are formed in the lower portion of each bottom soil sample unit tube, a top cold plate structure is arranged at the upper end of the sample tube, and a bottom cold plate structure is arranged at the lower end of the sample tube. The invention can measure the permeability coefficient of the soil body after freeze thawing, is more convenient and quick, can realize not only a constant water head permeability test, but also a variable water head permeability test, and can measure the permeability coefficients of different height ranges of the soil body after unidirectional freeze thawing.

Inventors

• FAN WENHU
• LIU DAN
• LIU SUMEI
• ZHOU JIANAN
• DENG MINGRUI
• YU WEI
• ZHU WENBIN
• YU TIANCHEN
• ZHU JIANHANG
• FAN XIAOFENG
• ZUO XI
• CHEN YUZHI
• ZHOU GUIYUN
• JIANG YANBIN

Assignees

• 金陵科技学院

Dates

Publication Date

20260512

Application Date

20230808

Claims (6)

1. 1. The method for measuring the unidirectional freeze-thawing permeability coefficient of soil bodies in different height ranges is characterized by comprising a reservoir (1), a sample barrel (2), a top cold plate structure (3), a bottom cold plate structure (4), a water supply pipe structure (5) and a variable water head pipe (6), wherein the reservoir (1) is positioned above the sample barrel (2), overflow holes (11) are formed in the side face of the reservoir (1), the overflow holes (11) are used for controlling the water surface height of the reservoir (1), the sample barrel (2) comprises a plurality of soil sample unit barrels (21) stacked up and down, the soil sample unit barrels (21) are filled with soil samples to be measured, the soil samples to be measured in adjacent soil sample unit barrels (21) are separated by a water permeable structure (22), the water permeable structure (22) is used for isolating the soil samples to be measured and allowing water to freely pass through, water injection holes (21 a) are formed in the upper part of each soil sample unit barrel (21), the bottom of the reservoir (1) is respectively communicated with the water injection hole (21 b) of each soil sample unit barrel (21) through the water supply pipe structure (5), the soil sample unit barrels (21) are arranged at the top of each soil sample unit barrel (21) and the soil sample to be measured, the bottom cooling plate structure (4) is arranged at the lower end of a bottom soil sample to be detected and supplies cold, a bottom water inlet hole (21 c) is formed in the lower part of a bottom soil sample unit cylinder (21), one end of a water changing head pipe (6) is connected with the bottom of a reservoir (1), the other end of the water changing head pipe is connected with the water inlet hole (21 c), a water changing head pipe water injection end (61 a) is further arranged on the water changing head pipe (6), an external water source can inject water into the water changing head pipe (6) through the water changing head pipe water injection end (61 a), a water injection Kong Zhishui clamp is arranged on each water injection hole (21 a), a water drainage Kong Zhishui clamp is arranged on a water drainage hole (21 b), a bottom water inlet Kong Zhishui clamp is arranged on the bottom water inlet hole (21 c), and water changing head pipe water injection ends are respectively used for controlling the on-off of corresponding pipelines; the measuring method comprises the following steps: firstly, determining the filling mode of each soil sample unit cylinder (21) according to the property of a soil sample to be detected, namely taking representative undisturbed soil or preparing the soil sample if the soil sample is coarse-grained soil, filling the soil sample unit cylinders (21) with the representative undisturbed soil or preparing the soil sample by adopting a layered compaction method, vertically cutting the undisturbed soil sample or preparing the soil sample along the soil sample if the soil sample is fine-grained soil, filling the fine-grained soil sample into the soil sample unit cylinders (21), and stacking and fixing a plurality of soil sample unit cylinders (21) filled with the soil sample to be detected up and down; step two, closing all water stop clamps, adjusting the top cold plate structure (3) and the bottom cold plate structure (4) to the same temperature of more than 0 ℃ and keeping constant temperature for a preset time, and then adjusting the temperature of the top cold plate structure (3) or the bottom cold plate structure (4) to the temperature of less than 0 ℃ to realize the freezing of the soil sample to be detected in the soil sample unit cylinder (21) from top to bottom or from bottom to top; Step three, when the test soil sample is coarse-grained soil, opening a water injection hole (21 a) of the top soil sample unit cylinder (21), a water discharge hole (21 b) of the bottom soil sample unit cylinder (21), and closing water injection holes (21 a) of other soil sample unit cylinders (21) and water inlet holes (21 c) of the bottom soil sample unit cylinders; Step four, adjusting the overflow hole (11) of the reservoir (1) to be higher than the top end 1-2m of the top soil sample unit cylinder (21), continuously injecting water into the reservoir (1), enabling residual water to overflow from the overflow hole (11) of the reservoir (1) all the time, enabling the water discharge hole (21 b) of the bottom soil sample unit cylinder (21) to be continuously discharged without bubbles, realizing full saturation of soil samples, then starting a seepage test measurement, measuring the vertical distance from the water surface of the reservoir (1) to the water discharge hole (21 b), namely, a water head difference, starting a stopwatch, simultaneously taking the seepage water for a certain time at the water discharge hole (21 b) by using a measuring cylinder, and measuring the water temperature in the cylinder, wherein the vertical seepage coefficient is calculated by the formulas (1) and (2): (1) (2) wherein k T is the permeability coefficient of the water temperature ToC sample; q is the permeate water quantity within t seconds; l is seepage diameter which is equal to the height of the soil sample to be measured between the opened water injection hole and the drainage hole; A is the cross-sectional area of the soil sample to be measured; Δh is the water head; k 20 is the permeability coefficient of the soil sample to be measured at the standard temperature of 20 ℃; η T is the dynamic viscosity coefficient of the ToC water; η 20 is the dynamic viscosity coefficient of 20 ℃ water; Step five, adjusting the height of overflow holes (11) of a reservoir (1) to change water head difference, repeating the step four to obtain a plurality of vertical permeability coefficients, and taking the average value of the vertical permeability coefficients as the permeability coefficient of a to-be-measured soil sample height range between a top soil sample unit cylinder (21) and a bottom soil sample unit cylinder (21); Step six, closing the water injection hole (21 a) of the top soil sample unit cylinder (21), opening the water injection hole (21 a) of the next soil sample unit cylinder (21), still keeping the water discharge hole (21 b) of the bottom soil sample unit cylinder (21) open, closing the water injection holes (21 a) of other soil sample unit cylinders (21) and the water inlet holes (21 c) of the bottom soil sample unit cylinders, and obtaining the permeability coefficient of the soil sample height range to be measured between the next soil sample unit cylinder (21) and the bottom soil sample unit cylinder (21) according to the fourth and fifth steps, and so on, obtaining the permeability coefficient of the soil sample height range to be measured between each soil sample unit cylinder (21) and the bottom soil sample unit cylinder (21); step seven, according to the permeability coefficient of the soil sample height range to be measured between each soil sample unit cylinder (21) and the bottom soil sample unit cylinder (21), obtaining the permeability coefficient of the soil sample height range to be measured between each soil sample unit cylinder (21) through inverse calculation of formulas (3) and (4); (3) (4) Wherein H j is the thickness of the soil sample to be detected of the jth soil sample unit cylinder (21); H is the total soil sample thickness to be measured, and the total soil sample to be measured consists of soil samples to be measured in n soil sample unit cylinders (21); k z is the vertical equivalent permeability coefficient of the soil sample to be measured with the thickness of H; k j is the vertical permeability coefficient of the soil sample to be detected of the jth soil sample unit cylinder (21); Step eight, when the test soil sample is fine soil, opening a water injection hole (21 a) of the top soil sample unit cylinder (21) and a water inlet hole (21 c) of the bottom soil sample unit cylinder (21), closing water injection holes (21 a), water discharge holes (21 b) and water injection ends (61 a) of water change head pipes of other soil sample unit cylinders (21), and dismantling a water supply pipe structure (5); Step nine, adjusting the overflow hole (11) of the reservoir (1) to be higher than the top end 1-2m of the top soil sample unit cylinder (21), filling water in the reservoir (1) into the bottom soil sample unit cylinder (21) through the water-changing head pipe (6), overflowing water from the water-filling hole (21 a) of the top soil sample unit cylinder (21), and ensuring that no bubbles exist in the water, so as to realize full saturation of soil samples, starting to perform seepage test measurement, emptying the water in the reservoir (1), opening the water-changing head pipe water-filling end (61 a), starting to measure the initial water head height and the initial time in the water-changing head pipe (6) after filling the water into the water-changing head pipe (6) to a required height, measuring the change of the water-changing head and the time according to a preset time interval, and measuring the water temperature of the water-filling hole (21 a) of the top soil sample unit cylinder (21), wherein the vertical permeability coefficient is calculated by formulas (2) and (5): (5) wherein: Is the sectional area of the variable water head pipe (6); h 1 is the head of the water at the beginning; h 2 is the water head at the end; then the water level of the variable water head pipe (6) is raised to the required height, and then the seepage test is carried out, and the measurement is repeated for a plurality of times, so that the obtained seepage coefficient is averaged to obtain the seepage coefficient of the soil sample height range to be measured between the top soil sample unit cylinder (21) and the bottom soil sample unit cylinder (21); Step ten, closing the water injection hole (21 a) of the top soil sample unit cylinder (21), opening the water injection hole (21 a) of the next soil sample unit cylinder (21), and obtaining the permeability coefficient of the soil sample height range to be measured between the next soil sample unit cylinder (21) and the bottom soil sample unit cylinder (21) according to step nine; Eleventh, according to the permeability coefficient of the soil sample height range to be measured between each soil sample unit cylinder (21) and the bottom soil sample unit cylinder (21), the permeability coefficient of the soil sample height range to be measured between each soil sample unit cylinder (21) is obtained through back calculation of formulas (3) and (4).
2. 2. The method for measuring the unidirectional freeze thawing permeability coefficient of soil bodies in different height ranges according to claim 1, wherein the top cold plate structure (3) and the bottom cold plate structure (4) have the same structure and comprise a cold cavity (31), a cold pipe (32) and a cold bath (33), the cold cavity (31) is attached to the upper end of a top soil sample to be measured or the lower end of the bottom soil sample to be measured, the cold cavity (31) and the cold bath (33) form a loop through the cold pipe (32), and a cooling liquid flows in the loop, and the cold bath (33) is used for cooling the cooling liquid.
3. 3. The method for measuring the unidirectional freeze-thawing permeability coefficient of soil bodies in different height ranges according to claim 2 is characterized in that a water-stop rubber ring (23) is arranged at the joint of the cylinder edges of the adjacent soil sample unit cylinders (21), and the water-stop rubber ring (23) is used for preventing water and a soil sample to be measured from exuding from the cylinder edges of the adjacent soil sample unit cylinders (21).
4. 4. The method for measuring the unidirectional freeze-thawing permeability coefficient of soil bodies in different height ranges according to claim 1, wherein the coarse granular soil is granular soil with a grain size of more than 0.075mm, and the fine granular soil is granular soil with a grain size of less than or equal to 0.075 mm.
5. 5. The method for measuring the unidirectional freeze-thawing permeability coefficient of soil bodies in different height ranges according to claim 1 is characterized in that scales are arranged on the variable water head pipe (6).
6. 6. The method for measuring the unidirectional freeze-thawing permeability coefficient of soil bodies in different height ranges according to claim 5 is characterized in that the inner diameter of the variable water head pipe (6) is not more than 1cm, the length is more than 1m, and the graduation value of graduations is 1mm.

Description

Device and method for measuring and testing unidirectional freeze-thawing permeability coefficients of soil bodies in different height ranges Technical Field The invention belongs to the technical field of geotechnical experiments, and particularly relates to a device and a method for measuring and testing unidirectional freeze-thawing permeability coefficients of soil bodies in different height ranges. Background Whether the soil is roadbed soil in a seasonal frozen soil area or a soil layer reinforced by an artificial freezing method, the soil is affected by freeze thawing, the water phase change and redistribution in the soil in the freeze thawing process can change the structure of the soil, the permeability of the soil is changed, the damage degradation of the mechanical property of the soil is further caused, and even engineering disasters are caused, so that the research on the permeability of the soil after freeze thawing has important significance, and an important reference basis can be provided for design and construction. The permeability coefficient is an important index for representing the permeability of the soil body, the conventional indoor permeability test is divided into a constant water head permeability test and a variable water head permeability test, wherein the constant water head permeability test is used for coarse-grained soil, the variable water head permeability test is used for fine-grained soil, two different sets of test equipment are adopted, only the permeability coefficient of the normal-temperature soil can be measured, and if the permeability coefficient is used for measuring the permeability coefficient of the soil body after freeze thawing, the two tests of the freeze thawing test and the permeability test are combined, so that no integrated test device for measuring the permeability coefficient of the soil body after freeze thawing exists at present. In addition, the indoor soil freezing and thawing test generally adopts unidirectional freezing and natural thawing to simulate the freezing and thawing process of the soil, and due to the influence of temperature gradient, pores at different heights of the frozen and thawed soil can change to different degrees, so that permeability coefficients of different height ranges are different, and research on the permeability coefficients of the soil in different height ranges can provide important theoretical basis for revealing the change of mechanical properties of the frozen and thawed soil, and no test method for measuring the vertical permeability coefficients of the frozen and thawed soil in different height ranges exists at present. Disclosure of Invention Aiming at the problems mentioned in the background art, the invention provides a device and a method for measuring the unidirectional freeze-thawing permeability coefficient of soil bodies in different height ranges. In order to achieve the technical purpose, the invention adopts the following technical scheme: The utility model provides a unidirectional freezing and thawing permeability coefficient measurement test device of not high within range soil body, including the cistern, the sample section of thick bamboo, top cold plate structure, bottom cold plate structure, delivery pipe structure and change water head pipe, the cistern is located sample section of thick bamboo top, the cistern side is provided with the overflow hole, the overflow hole is used for controlling the surface of water height of cistern, the sample section of thick bamboo includes a plurality of soil sample unit section of thick bamboo that stacks from top to bottom, fill full soil sample that awaits measuring in the soil sample unit section of thick bamboo, pass through the permeable structure separation between the soil sample that awaits measuring in the adjacent soil sample unit section of thick bamboo, allow water free passage when the structure isolation awaits measuring the soil sample that permeates water, every soil sample unit section of thick bamboo upper portion is provided with the water injection hole, the water discharge hole has been seted up to the cistern bottom through the delivery pipe structure respectively with the water injection hole of every soil sample unit section of thick bamboo, top cold plate structure is installed in top soil sample upper end and is supplied cold, bottom cold plate structure is installed in bottom soil sample unit section of thick bamboo lower extreme that awaits measuring and is supplied cold, bottom water inlet opening is seted up to bottom soil sample unit section of thick bamboo lower part, change water head pipe one end and reservoir bottom connection, the other end and water inlet connection, change water head pipe upper portion and the soil sample unit section of thick bamboo and the soil sample that awaits measuring. In order to optimize the technical scheme, the specific measures adopted further comprise: The water injection Kong Zhishui