LU504146B1

LU504146B1 - Specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities

Info

Publication number: LU504146B1
Application number: LU504146A
Authority: LU
Inventors: Yong Wang; Junjie Zhang
Original assignee: Inst Rock & Soil Mech Cas; China Railway Major Bridge Reconnaissance & Design Inst Co Ltd
Priority date: 2023-05-08
Filing date: 2023-05-08
Publication date: 2024-05-14

Abstract

A specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities is disclosed. The device includes a reaction kettle, a stirrer and a specimen box. The reaction kettle has a top communicated with a bottom of the specimen box through a high-pressure tube. The stirrer, pH transducer and temperature transducer are mounted in the reaction kettle correspondingly. The top of the reaction kettle is communicated with an air inlet pipe and vacuum pressure gauge. The reaction kettle has a bottom communicated with a water inlet pipe. The bottom of the reaction kettle is communicated with a top of the specimen box through a soil paste flowing pipe. The bottom of the specimen box is communicated with vacuum pressure gauge. According to the present disclosure, gassy soil specimens with varying densities may be prepared massively and controllably that meet the requirements of geotechnical tests.

Description

BL-5676

SPECIMEN PREPARATION DEVICE CAPABLE FOR QUANTITATIVE 10506168

PREPARATION OF GASSY SOIL SPECIMENS WITH VARYING DENSITIES

TECHNICAL FIELD

[01] The present disclosure relates to the technical field of geotechnical tests for geotechnical engineering, more particular to a specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities, especially relating to technologies of laboratory artificial simulated specimen preparation for submarine gassy sediments.

BACKGROUND ART

[02] Gassy soil refers specifically to the soil in which gas occurs in a closed free or dissolved state rather than gas hydrates state. It is considered as a metastable equilibrium body composed of soil particles, pore water, gas, temperature and overburden pressure. Once the equilibrium is broken, its engineering behaviors will change rapidly and cause disasters to the project. For example, submarine gassy sediments often cause disasters such as coastal landslides, soil liquefaction and foundation subsidence, which are major safety hazards in marine engineering.

[03] The gassy soil is widely distributed in nature, but the research carried out for it is very limited. The major trouble lies in that the gas in the soil is of high pressure and instable, which is easy to decompose, exsolve and escape, hence destroying the original structure of the soil. It is difficult to obtain the original field gassy soil specimens. Even if special equipment can be employed to obtain undisturbed soil specimens under pressure, there are still problems such as the difficulty of laboratory secondary processing and uneven gas distribution in the soil specimens, which have prompted the development of methods for laboratory artificial preparation of gassy soil and the study of engineering characteristics of submarine gassy sediments through simulated preparation.

[04] At present, the methods for artificial preparation of gassy soil are as follows. (1)

Biological gas production method, which is difficult to quantitatively control the gas 1

BL-5676 production, difficult to repeat the preparation of specimens, and difficult to use for HUS04140 general laboratory triaxial tests. (2) Unsaturated soil method, which is suitable for preparing soil specimens with saturation less than 85%. However, the actual submarine gassy sediment has saturation generally greater than 85%. (3) GasTube method, in which method one end of a plastic pipe of a specific length is sealed, while the other end is connected to a soil specimen drain valve, so that the soil specimen and a known amount of gas form a closed system during the test. This method is difficult to prepare an element body specimen with good uniformity. (4) CO; saturated aqueous solution degasification method, the patent “High-pressure gas dissolved saturation test device and application thereof in artificial preparation of gassy soil specimen (ZL201410027361.5)” provides a method for preparing gassy soil specimens using a

CO; saturated aqueous solution degasification method. This method is suitable for sands with better water permeability, but it is not effective for clays with poor water permeability, especially for preparing gassy soil specimens with higher initial density.

SUMMARY

[05] In view of the shortcomings of the existing technologies, the present disclosure aims to provide a specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities. With this device, gassy soil specimens with varying densities may be prepared massively and controllably that meet the requirements of laboratory geotechnical tests.

[06] The aim of the present disclosure is implemented through the following technical solution.

[07] A specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities includes a reaction kettle, a stirrer and a specimen box.

The reaction kettle has a top communicated with a bottom of the specimen box through a high-pressure tube. The high-pressure tube is provided with a first valve at a position close to the top of the reaction kettle and a six valve at a position close to the bottom of the specimen box. The stirrer is mounted in the reaction kettle correspondingly. The top of the reaction kettle is communicated with an air inlet pipe and a first vacuum pressure 2

BL-5676 gauge. The air inlet pipe being provided with a third valve. A pH transducer and a HUS04140 temperature transducer are arranged in the reaction kettle correspondingly. The reaction kettle has a bottom communicated with a water inlet pipe, and the water inlet pipe is provided with a fourth valve and a second flowmeter correspondingly. The bottom of the reaction kettle is communicated with a top of the specimen box through a soil paste flowing pipe. The soil paste flowing pipe has a middle part provided with a first flowmeter, and the soil paste flowing pipe is further provided with a second valve and a fifth valve. The second valve and the fifth valve are located at two sides of the first flowmeter. The bottom of the specimen box is communicated with a second vacuum pressure gauge. The specimen box includes a cylinder top cover, a forming cylinder B and a cylinder bottom cover. The cylinder top cover is detachably and sealingly mounted on a top of the forming cylinder B. The cylinder bottom cover is detachably and sealingly mounted on a bottom of the forming cylinder B, and the cylinder top cover is provided with a pushing piston having scale.

[08] To better implement the present disclosure, the pushing piston includes a pushing rod, a pushing handle and a pushing piston plate. The pushing rod penetrates through the cylinder top cover. The pushing rod has a top end fixed to the pushing handle, and the pushing rod has a bottom end fixed to the pushing piston plate. The pushing piston plate is located inside the forming cylinder B. The pushing handle is located outside the specimen box. The pushing rod is provided with scale lines along a height direction.

[09] Preferably, the reaction kettle includes a forming cylinder A and a sealing cover covering and sealing a top opening of the forming cylinder A. The sealing cover is connected and fixed to a top of the forming cylinder A through a plurality of bolts. Both the air inlet pipe and the first vacuum pressure gauge are communicated with the sealing cover. The high-pressure tube is communicated with the sealing cover.

[10] Preferably, the specimen preparation device further includes a vacuum pump, a

CO» storage tank and a water injection tank. The vacuum pump is provided with a vacuumizing pipe, corresponding to the air inlet pipe. The CO; storage tank is provided with an air outlet pipe, corresponding to the air inlet pipe. 3

BL-5676

[11] Preferably, the cylinder bottom cover of the specimen box is provided with a HUS04140 porous stone and filter paper in turn from bottom to top.

[12] Preferably, the stirrer includes a stirring motor, a stirring shaft and stirring paddles. The stirring shaft rotatably penetrates through and is mounted on the sealing cover. The stirring shaft is mounted with a plurality of stirring paddles. All the stirring paddles are located inside the forming cylinder A. The stirring motor is mounted on the sealing cover, and the stirring motor has a power output shaft dynamically connected to the stirring shaft.

[13] Preferably, the pH transducer has a probe penetrating through the sealing cover and located inside the forming cylinder A, and the temperature transducer has a probe penetrating through the sealing cover and located inside the forming cylinder A.

[14] Preferably, the high-pressure tube has an end part communicated with the cylinder bottom cover, the soil paste flowing pipe has a bottom end communicated with the cylinder top cover, and the second vacuum pressure gauge is communicated with the bottom of the forming cylinder B.

[15] Compared to the existing technologies, the present disclosure has the following advantages and beneficial effects.

[16] (1) With the device provided by the present disclosure, gassy soil specimens with varying densities may be prepared massively and controllably that meet the requirements of laboratory geotechnical tests.

[17] (2) According to the specimen preparation device provided by the present disclosure, a saturated CO; aqueous solution is employed to generate a CO; gas through unloading and degasification and a pH transducer is employed to measure a pH value of the solution to monitor the dissolved amount of gas, thereby achieving the quantitative control of gas content in the gassy soil. Further, proportioning is enabled through various flowmeters to obtain a soil paste with precise data. Then, the soil paste is metered before flowing into the specimen box, and the soil paste is consolidated and compressed through a pushing piston with scale lines to obtain a soil specimen with a required height, thus preparing gassy soil specimens with varying densities.

[18] (3) The present disclosure is applicable to a wide range of soil types, which not 4

BL-5676 only is applicable to coarse-grained sandy soil, but also applicable to fine-grained clay HUS04140 soil. In addition, the present disclosure is not restricted by the densities of the specimens to be prepared. The soil specimen prepared has a uniform gas distribution, the preparation of gassy soil can be repeated, the preparation efficiency is high, the assembling of the device is simple, and the cost is low.

[19] (4) According to the present disclosure, gassy soil specimens required for various geotechnical tests (for example, one-dimensional compression tests, triaxial tests, cyclic shear tests, etc.) can be prepared by employing different sizes of specimen boxes, for use in the geotechnical test study of different characteristics of the gassy soil.

BRIEF DESCRIPTION OF THE DRAWINGS

[20] FIG 1 is a structure diagram of the present disclosure.

[21] Below is the description of designators in the figure.

[22] 100-pH transducer, 101-temperature transducer, 102-first flowmeter, 103-first vacuum pressure gauge, 104-second flowmeter, 105-second vacuum pressure gauge, 2-reaction kettle, 201-first valve, 202-sealing cover, 203-high-pressure tube, 204-forming cylinder A, 205-second valve, 206-air inlet pipe, 207-third valve, 208-bolt, 209-stirrer, 210-soil specimen, 211-fourth valve, 212-water inlet pipe, 3-specimen box, 300-fifth valve, 301-cylinder top cover, 302-forming cylinder B, 303-cylinder bottom cover, 304-six valve, 305-pushing piston, 306-scale line, 307-filter paper, 308-porous stone, 4-soil paste flowing pipe.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[23] The present disclosure is described below in further detail conjunction with embodiments.

[24] Embodiment 1

[25] As shown in FIG 1, a specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities includes a reaction kettle 2, a stirrer 209 and a specimen box 3. The reaction kettle 2 has a top communicated with a bottom of the specimen box 3 through a high-pressure tube 203. The high-pressure tube

BL-5676 203 is provided with a first valve 201 at a position close to the top of the reaction kettle HUS04140 2 and a six valve 304 at a position close to the bottom of the specimen box 3. The stirrer 209 is mounted in the reaction kettle 2 correspondingly. The top of the reaction kettle 2 is communicated with an air inlet pipe 206 and a first vacuum pressure gauge 103. The air inlet pipe 206 is provided with a third valve 207. A pH transducer 100 and a temperature transducer 101 are arranged in the reaction kettle 2 correspondingly. The reaction kettle 2 has a bottom communicated with a water inlet pipe 212, and the water inlet pipe 212 is provided with a fourth valve 211 and a second flowmeter 104 correspondingly. The bottom of the reaction kettle 2 is communicated with a top of the specimen box 3 through a soil paste flowing pipe 4. The soil paste flowing pipe 4 has a middle part provided with a first flowmeter 102. The soil paste flowing pipe 4 is further provided with a second valve 205 and a fifth valve 300. The second valve 205 and the fifth valve 300 are located at two sides of the first flowmeter 102. The bottom of the specimen box 3 is communicated with a second vacuum pressure gauge 105. The specimen box 3 includes a cylinder top cover 301, a forming cylinder B302 and a cylinder bottom cover 303. The cylinder top cover 301 is detachably and sealingly mounted on a top of the forming cylinder B302. The cylinder bottom cover 303 is detachably and sealingly mounted on a bottom of the forming cylinder B302. The cylinder top cover 301 is provided with a pushing piston 305 having scale. The specimen box 3 is internally provided with a porous stone 308 and filter paper 307 in turn from bottom to top. The porous stone 308 and the filter paper 307 are located inside the cylinder bottom cover 303 in turn from bottom to top.

[26] As shown in FIG 1, the pushing piston 305 includes a pushing rod, a pushing handle and a pushing piston plate. The pushing rod penetrates through the cylinder top cover 301. The pushing rod has a top end fixed to the pushing handle, and the pushing rod has a bottom end fixed to the pushing piston plate. The pushing piston plate is located inside the forming cylinder B302. The pushing handle is located outside the specimen box 3. The pushing rod is provided with scale lines 306 along a height direction.

[27] As shown in FIG 1, the reaction kettle 2 includes a forming cylinder A204 and 6

BL-5676 a sealing cover 202 covering and sealing a top opening of the forming cylinder A204. 7504746

The sealing cover 202 is connected and fixed to a top of the forming cylinder A204 through a plurality of bolts 208. Both the air inlet pipe 206 and the first vacuum pressure gauge 103 are communicated with the sealing cover 202. The high-pressure tube 203 is communicated with the sealing cover 202.

[28] The present disclosure further includes a vacuum pump, a CO; storage tank and a water injection tank. The vacuum pump is provided with a vacuumizing pipe, corresponding to the air inlet pipe 206. The CO» storage tank is provided with an air outlet pipe, corresponding to the air inlet pipe 206.

[29] As shown in FIG 1, the stirrer 209 includes a stirring motor, a stirring shaft and stirring paddles. The stirring shaft rotatably penetrates through and is mounted on the sealing cover 202. The stirring shaft is mounted with a plurality of stirring paddles. All the stirring paddles are located inside the forming cylinder A204. The stirring motor is mounted on the sealing cover 202, and the stirring motor has a power output shaft dynamically connected to the stirring shaft.

[30] The pH transducer 100 in the preset disclosure is provided with a probe. The probe of the pH transducer 100 penetrates through the sealing cover 202 and is located inside the forming cylinder A204. The temperature transducer 101 in the present disclosure is provided with a probe. The probe of the temperature transducer 101 penetrates through the sealing cover 202 and is located inside the forming cylinder

A204.

[31] As shown in FIG 1, the high-pressure tube 203 has an end part communicated with the cylinder bottom cover 303. The soil paste flowing pipe 4 has a bottom end communicated with the cylinder top cover 301. The second vacuum pressure gauge 105 is communicated with the bottom of the forming cylinder B302.

[32] A specimen preparation method capable for quantitative preparation of gassy soil specimens with varying densities includes the following methods.

[33] Step A: a saturated porous stone 308 and filter paper 307 are placed on a cylinder bottom cover 303 in turn. A forming cylinder B302 is sealed by a cylinder top cover 301 and a cylinder bottom cover 303 to form a sealed specimen box 3. Then, the 7

BL-5676 assembled specimen box 3 is weighted, with a total mass of mo. Next, oven-dry soil HUS04140 with a mass of mi is placed into a forming cylinder A204, and the forming cylinder

A204 is sealed by a bolt 208 and a sealing cover 202 to form a sealed reaction kettle 2.

[34] Step B: the reaction kettle 2 is connected to the specimen box 3 through a high-pressure tube 203. A vacuumizing pipe of a vacuum pump is airtightly connected to air inlet pipe 206. A second valve 205 and a fourth valve 211 are turned off, while a first valve 201, a third valve 207, a fifth valve 300 and a sixth valve 304 are turned on.

Then, the vacuum pump is started to exhaust the air inside the reaction kettle 2, the specimen box 3 and the oven-dry soil. When a first vacuum pressure gauge 103 and a second vacuum pressure gauge 105 approach -100kPa, continue air pumping not less than 1.5 hours. Then, the third valve 207 is turned off. Next, a water inlet pipe 212 is immersed into degassed water inside a water injection tank, and the fourth valve 211 is turned on, so that the degassed water is slowly sucked into the forming cylinder A204 via the water inlet pipe 212. During the water injection process, the numerical value of the first vacuum pressure gauge 103 is kept unchanged, and the flow reading Vo of a second flowmeter is recorded. Finally, the fourth valve 211 is turned off.

[35] Step C: an air inlet pipe 206 is connected to a high-purity CO; storage tank, and a pressure relief valve of the CO; storage tank is adjusted, so that the pressure remains at 500kPa. Then, the third valve 207 is turned on. When the first vacuum pressure gauge 103 and the second vacuum pressure gauge 105 stabilize at S00kPa, the stirrer 209 is started to stir, so that the soil and the water are uniformly mixed to form a soil paste.

When a pH transducer 100 reads 5.60+0.02 (a theoretical pH value of a saturated CO» aqueous solution), the third valve 207 is turned off, the stirrer 209 is stopped, the pH value of the pH transducer 100 is recorded and the temperature value of the temperature transducer 101 is recorded.

[36] Step D: the second valve 205 and the fifth valve 300 are turned on. Under the force of gravity, the soil paste inside the reaction kettle 2 flows into the specimen box 3.

The flow is recorded through the first flowmeter 102. Then, the fifth valve 300 is turned off after the required soil paste flows into the specimen box 3.

[37] Step E: the sixth valve 304 is turned on, and a jack is employed to slowly push a 8

BL-5676 pushing piston 305, so that the soil paste 1s consolidated and compressed, until reaching HUS04140 a required height of a soil specimen 210. Keep still and wait until the water head discharged into the high-pressure tube 203 keeps unchanged more than 24 hours. Then, the sixth valve 304 is turned off, the soil paste flowing pipe 4 and the high-pressure tube 203 are demounted, and the specimen box 3 is totally moved into a freezing chamber to freeze and form. After forming, the cylinder bottom cover 303 of the specimen box 3 is screwed off, the soil specimen 210 is pushed out through the pushing piston 305, and the soil specimen 210 is quickly mounted on a pedestal of a geotechnical triaxial apparatus. Back pressure is controlled through a triaxial test system. Wait for the soil specimen 210 to melt. The back pressure is adjusted, so that the CO; gas dissolved in the pore water of the soil specimen 210 is slowly exsolved, until becoming stable.

[38] Embodiment 2

[39] The present embodiment takes submarine clay (particle size less than 0.075 mm, maximum specific gravity Gs of 2.73) as an object and prepares triaxial gassy soil specimens taking the geotechnical triaxial test as an example. Remolded soil is prepared according to “Standard for Geotechnical Testing Method” (GB/T50123), and fine-particle gassy soft soil specimens (test requirements include diameter d of 50 mm, height h of 100 mm, volume V; of 196.34 cm’) with varying densities (for example, test requirements include dry densities pa of 1.60, 1.65 and 1.70 g/cm’ respectively) are prepared based on the principle of bubble generation by unloading and degasification of a saturated CO, aqueous solution. Of course, the present disclosure is further applicable to the preparation of fine-particle gassy soft soil specimens required for other geotechnical tests. The test is carried out in a constant temperature laboratory environment. The specific specimen preparation includes the following steps.

[40] Step 1: assembling of device

[41] (1) A saturated porous stone 308 and filter paper 307 are placed on a cylinder bottom cover 303 in turn. A forming cylinder B302 is sealed by a cylinder top cover 301 and a cylinder bottom cover 303 to form a sealed specimen box 3. Then, the empty specimen box 3 is weighted, with a total mass of mo.

[42] mo=2620.66 g 9

BL-5676

[43] (2) 5 kg of oven-dry soil is placed into a forming cylinder A204. 7504746

[44] Oven-dry soil weight mı=5 kg

[45] (3) The forming cylinder A204 is sealed by a bolt 208 and a sealing cover 202 to form a sealed reaction kettle 2.

[46] (4) The reaction kettle 2 is airtightly connected to the specimen box 3 through a high-pressure tube 203. A second valve 205 and a fourth valve 211 are turned off, while a first valve 201, a third valve 207, a fifth valve 300 and a sixth valve 304 are turned on.

[47] Step 2: preparation of specimen

[48] (1) Air inlet pipe 206 is connected to a vacuum pump. The vacuum pump is started to exhaust the air inside the reaction kettle 2, the specimen box 3 and the oven-dry soil. When a first vacuum pressure gauge 103 and a second vacuum pressure gauge 105 approach -100kPa, continue air pumping not less than 1.5 hours. Then, the third valve 207 is turned off. Next, a water inlet pipe 212 is immersed into degassed water (the degassed water has a density p of 1 g/cm?) inside a water injection tank, and the fourth valve 211 is turned on, so that the degassed water is slowly sucked into the forming cylinder A204 via the water inlet pipe 212. During the water injection process, the numerical value of the first vacuum pressure gauge 103 is kept unchanged. When a second flowmeter reads 5 L, the fourth valve 211 is turned off.

[49] Injected water volume Vo=5 L. According to the formula Mwate=Voxp, the calculated mass of the injected water is Mwater=5 kg.

[50] (2) An air inlet pipe 206 is connected to a high-purity CO; storage tank, and a pressure relief valve of the CO; storage tank is adjusted, so that the pressure remains at 500kPa. Then, the third valve 207 is turned on. When the first vacuum pressure gauge 103 and the second vacuum pressure gauge 105 stabilize at S00kPa, the stirrer 209 is started to stir, so that the soil and the water are uniformly mixed to form a soil paste.

When a pH transducer 100 reads 5.60 (a theoretical pH value of a saturated CO; aqueous solution), the third valve 207 is turned off, the stirrer 209 is stopped, the pH value of the pH transducer 100 is recorded as 5.60 and the temperature value of the temperature transducer 101 is recorded as 25°C.

[51] Step 3: forming of soil specimen

BL-5676

[52] (1) The second valve 205 and the fifth valve 300 are turned on. Under the force 7504746 of gravity, the soil paste inside the reaction kettle 2 flows into the specimen box 3. The flow is recorded through the first flowmeter 102 (reset is needed before usage) Then, the fifth valve 300 is turned off after the required soil paste flows into the specimen box 3, when the first flowmeter 102 reads 100 ml. The soil paste volume V1 inside the specimen box 3 is:

[53] V1=100 cm}

[54] The specimen box 3 and the interior soil paste are weighted, with a total mass of mi.

[55] mı=2796.11 g

[56] (2) The density p of the soil paste is calculated according to the density p formula in soil mechanics. [571 p=m/V;

[58] where p indicates the density of the soil paste (g/cm?);

[59] m indicates the mass of the soil paste (g); and

[60] V indicates the volume of the soil paste (cm?)

[61] The soil paste mass m=mi-mp=2796.11-2620.66=175.45 g, the soil paste volume V=V,=100 cm’, then the soil paste density p=1.7545 g/cm’ (the soil paste density Ppaste is 1.7545 g/cm’).

[62] A water content w of the soil paste is calculated according to a water content w formula,

[63] wm,

[64] where w indicates the water content of the soil paste;

[65] my indicates the mass (g) of the water; and

[66] ms indicates the mass (g) of the dry soil.

[67] The water mass my =Mwater=VoXPwater=5 kg, ms=mi=5 kg, and the obtained water content of the soil paste is 100%.

[68] The dry density pa of the soil paste is calculated according to a formula.

[69] pa=p/(1+w); 11

BL-5676

[70] The soil paste density ppaste is 1.7545 g/cm’, then the dry density pa is 0.877 HUS04140 g/cm’. The dry density pa is correct to three decimal places.

[71] Fine-particle gassy soft soil specimens (diameter d of 50 mm, height h of 100 mm, volume V» of 196.34 cm?) with dry densities of 1.60 g/cm’, 1.65 g/cm? and 1.70 g/cm’ are prepared using the soil paste with a dry density pa of 0.877 g/cm’ and a water content of 100%. According to the density formula ma= paxV, the dry soil mass (correct to two decimal places) required for the above three different densities are as follows respectively.

[72] The fine-particle gassy soft soil specimen with a dry density of 1.60 g/cm’ requires a dry soil mass ma:=V2<1.60=314.14 g.

[73] The fine-particle gassy soft soil specimen with a dry density of 1.65 g/cm’ requires a dry soil mass ma=V2<1.65=324.16 g.

[74] The fine-particle gassy soft soil specimen with a dry density of 1.70 g/cm’ requires a dry soil mass mas=V2*1.70=333.78 g.

[75] Herein, Mai, Ma and mas are dry soil masses corresponding to dry densities of 1.60 g/cm’, 1.65 g/em* and 1.70 g/cm’ respectively. According to the mass formula m=ma(1+w), the masses of the required soil paste (the soil paste with a dry density pa of 0.877 g/cm’ and a water content of 100% is the soil paste already prepared by the present embodiment) are as follows respectively.

[76] The fine-particle gassy soft soil specimen with a dry density of 1.60 g/cm’ requires a soil paste mass m=628.28 g.

[77] The fine-particle gassy soft soil specimen with a dry density of 1.65 g/cm’ requires a soil paste mass m3=648.32 g.

[78] The fine-particle gassy soft soil specimen with a dry density of 1.70 g/cm’ requires a soil paste mass my=667.56 g.

[79] The soil paste prepared by the present embodiment has a density Ppaste Of 1.7545 g/cm’. According to the density formula p=m/V, the soil paste volumes (correct to two decimal places) corresponding to my, M3 and m4 are as follows respectively.

[80] The fine-particle gassy soft soil specimen with a dry density of 1.60 g/cm’ requires a soil paste volume V,=358.10 cm*=358.10 ml. 12

BL-5676

[81] The fine-particle gassy soft soil specimen with a dry density of 1.65 g/cm’ HUS04140 requires a soil paste volume V3=369.52 cm*—369.52 ml.

[82] The fine-particle gassy soft soil specimen with a dry density of 1.70 g/cm’ requires a soil paste volume V4=380.48 cm’ =380.48 ml.

[83] Therefore, the soil specimens 210 with dry densities of 1.60 g/em*, 1.65 g/cm’, 1.70 g/cm’ correspond to soil paste flows of 358.10 ml, 369.52 ml and 380.48 ml respectively.

[84] (3) The fifth valve 300 is turned on again, so that the soil paste inside the reaction kettle 2 continues flowing into the specimen box 3. When the first flowmeter 102 reads 358.10 ml (or 369.52 ml, 380.48 ml) from 100 ml, the fifth valve 300 is turned off. Then the sixth valve 304 is turned on, and a jack is employed to slowly push a pushing piston 305, so that the soil paste in the specimen box 3 is consolidated and compressed, until reaching the scale line 306 of 100 mm (the required specimen height is 100 mm) on the pushing rod. Keep still and wait until the water head discharged into the high-pressure tube 203 keeps unchanged more than 24 hours. Then, the first valve 201, the second valve 205 and the sixth valve 304 are turned off. The fifth valve 300 and the tube on the outer end of the sixth valve 304 are demounted. The specimen box 3 is totally moved into a freezing chamber to freeze and form. After forming, the cylinder bottom cover 303 of the specimen box 3 is screwed off, the soil specimen 210 is pushed out through the pushing piston 305, and the soil specimen 210 is quickly mounted on a pedestal of a geotechnical triaxial apparatus. Back pressure is controlled through a triaxial test system. Wait for the soil specimen 210 to melt. The back pressure is adjusted, so that the CO; gas dissolved in the pore water of the soil specimen 210 is slowly exsolved, until becoming stable. The temperature and pressure are recorded. The relationship between the CO; gas exsolved amount and the pressure is determined according to the Henry laws, thereby achieving the preparation of the gassy soil specimen with an initial dry density of 1.60 g/cm? (1.65 g/cm’ or 1.70 g/cm?).

[85] Besides the fine-particle gassy soft soil specimens (test requirements include diameter d of 50 mm, height h of 100 mm, volume V2 of 196.34 cm’, dry densities of 1.60, 1.65 and 1.70 g/cm’ respectively) required for geotechnical tests in the present 13

BL-5676 embodiment, the present disclosure can also prepare fine-particle gassy soft soil HUS04140 specimens meet the requirement specifications of other geotechnical tests. The present embodiment merely describes the preparation method of the present disclosure by taking the preparation of the fine-particle gassy soft soil specimens (test requirements include diameter d of 50 mm, height h of 100 mm, volume V3 of 196.34 cm’, dry densities of 1.60, 1.65 and 1.70 g/cm’ respectively) for example.

[86] The above are preferred embodiments of the present disclosure merely and are not intended to limit the present disclosure. Any modifications, equivalent substitutions and changes and the like made within the spirit and principle of the present disclosure are all intended to be included in the scope of protection of the present disclosure. 14

Claims

BL-5676 CLAIMS: LU504146

1. À specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities, comprising a reaction kettle (2), a stirrer (209) and a specimen box (3), the reaction kettle (2) having a top communicated with a bottom of the specimen box (3) through a high-pressure tube (203), the high-pressure tube (203) being provided with a first valve (201) at a position close to the top of the reaction kettle (2) and a six valve (304) at a position close to the bottom of the specimen box (3), the stirrer (209) being mounted in the reaction kettle (2) correspondingly, the top of the reaction kettle (2) being communicated with an air inlet pipe (206) and a first vacuum pressure gauge (103), the air inlet pipe (206) being provided with a third valve (207), a pH transducer (100) and a temperature transducer (101) being arranged in the reaction kettle (2) correspondingly, the reaction kettle (2) having a bottom communicated with a water inlet pipe (212), the water inlet pipe (212) being provided with a fourth valve (211) and a second flowmeter (104) correspondingly, the bottom of the reaction kettle (2) being communicated with a top of the specimen box (3) through a soil paste flowing pipe (4), the soil paste flowing pipe (4) having a middle part provided with a first flowmeter (102), the soil paste flowing pipe (4) being further provided with a second valve (205) and a fifth valve (300), and the second valve (205) and the fifth valve (300) being located at two sides of the first flowmeter (102).

2. The specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities according to claim 1, wherein the bottom of the specimen box (3) is communicated with a second vacuum pressure gauge (105), the specimen box (3) comprises a cylinder top cover (301), a forming cylinder B (302) and a cylinder bottom cover (303), the cylinder top cover (301) is detachably and sealingly mounted on a top of the forming cylinder B (302), the cylinder bottom cover (303) is detachably and sealingly mounted on a bottom of the forming cylinder B (302), and the cylinder top cover (301) is provided with a pushing piston (305) having scale.

3. The specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities according to claim 2, wherein the pushing piston

BL-5676 (305) comprises a pushing rod, a pushing handle and a pushing piston plate, the pushing HUS04140 rod penetrates through the cylinder top cover (301), the pushing rod has a top end fixed to the pushing handle, the pushing rod has a bottom end fixed to the pushing piston plate, the pushing piston plate is located inside the forming cylinder B (302), the pushing handle is located outside the specimen box (3), and the pushing rod is provided with scale lines (306) along a height direction.

4. The specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities according to claim 1, wherein the reaction kettle (2) comprises a forming cylinder A (204) and a sealing cover (202) covering and sealing a top opening of the forming cylinder A (204), the sealing cover (202) is connected and fixed to a top of the forming cylinder A (204) through a plurality of bolts (208), both the air inlet pipe (206) and the first vacuum pressure gauge (103) are communicated with the sealing cover (202), and the high-pressure tube (203) is communicated with the sealing cover (202).

5. The specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities according to claim 1, further comprising a vacuum pump, a CO; storage tank and a water injection tank, the vacuum pump being provided with a vacuumizing pipe corresponding to the air inlet pipe (206), and the CO, storage tank being provided with an air outlet pipe corresponding to the air inlet pipe (206).

6. The specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities according to claim 4, wherein the stirrer (209) comprises a stirring motor, a stirring shaft and stirring paddles, the stirring shaft rotatably penetrates through and is mounted on the sealing cover (202), the stirring shaft is mounted with a plurality of stirring paddles, all the stirring paddles are located inside the forming cylinder A (204), the stirring motor is mounted on the sealing cover (202), and the stirring motor has a power output shaft dynamically connected to the stirring shaft.

7. The specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities according to claim 4, wherein the pH transducer 16

BL-5676 (100) has a probe penetrating through the sealing cover (202) and located inside the HUS04140 forming cylinder A (204), and the temperature transducer (101) has a probe penetrating through the sealing cover (202) and located inside the forming cylinder A (204).

8. The specimen preparation device capable for quantitative preparation of gassy soil specimens with varying densities according to claim 2 or 3, wherein the high-pressure tube (203) has an end part communicated with the cylinder bottom cover (303), the soil paste flowing pipe (4) has a bottom end communicated with the cylinder top cover (301), and the second vacuum pressure gauge (105) is communicated with the bottom of the forming cylinder B (302). 17