CN113237808A - Indoor test device for measuring bentonite permeation diffusion under THMC coupling effect and diffusion coefficient measuring method - Google Patents
Indoor test device for measuring bentonite permeation diffusion under THMC coupling effect and diffusion coefficient measuring method Download PDFInfo
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- G01N15/082—Investigating permeability by forcing a fluid through a sample
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N13/04—Investigating osmotic effects
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Abstract
The invention discloses an indoor test device for measuring bentonite permeation diffusion under THMC coupling effect and a diffusion coefficient measuring method. The pressure endowing device comprises an air pressure manufacturing machine, a pressure reducing valve, a pressure controller and a percolate supplementing box, and can meet the test control of a seepage field and a stress field; the infiltration diffusion test device mainly comprises an organic glass cylinder with an infiltration cabin inside, a constant temperature control device, a water inlet head water pipe and other structures, and can meet the test control of a temperature field and a chemical field; the test data processing device comprises a conductance detection sheet, a tail liquid collecting and measuring box, a post-processing computer and the like. Meanwhile, the invention provides a method for measuring the diffusion coefficient. After the conductivity of the bentonite is measured by the device in a sectional, layered and time-sharing manner, the diffusion coefficient in an unsteady state can be obtained by utilizing theoretical solution calculation, and the diffusion coefficient can be summarized and calculated after post-processing by a computer.
Description
Technical Field
The invention relates to the cross category of environmental geotechnical discipline and geosynthetic material discipline, and relates to an indoor test device for measuring bentonite permeation and diffusion under the coupling action of temperature-seepage-stress-chemistry (Thermal-Hydraulic-Mechanical-Chemical, THMC) and a method for measuring a diffusion coefficient.
Background
At present, the landfill is a garbage disposal method applied and popularized in all major and middle cities in China, and a composite lining seepage-proofing system is adopted in a seepage-proofing system in a garbage landfill site specified in technical Specification for domestic garbage landfill (CJJ 17-2004). The main component of the geotextile bentonite liner is bentonite, and the bentonite has a low permeability coefficient after absorbing water and expanding, so the geotextile bentonite liner is widely applied to seepage-proofing system engineering.
In the long-term operation process of the landfill, due to the effects of garbage accumulation, external rainfall, microbial decomposition and the like, bentonite is often under the multi-field coupling effect of complex temperature-seepage-stress-chemistry (Thermal-hydralic-Mechanical-Chemical, short for THMC). The permeability coefficient and the pollutant diffusion range of the bentonite under different working conditions are difficult to rapidly measure and analyze on site. The indoor test is a relatively common research method, but few indoor test devices for performing permeability coefficient and pollutant diffusion by the THMC coupling method are available.
Meanwhile, when measuring the diffusion coefficient, a diffusion column is generally used, but has certain disadvantages: 1) sampling is accidental, so that the error of diffusion coefficient measurement is caused; 2) only the diffusion coefficient at the termination of the test is obtained, the diffusion coefficient in the test process cannot be obtained, and the breakdown of the bentonite by the chemical ions is effectively monitored; 3) the multi-field coupling cannot be completed due to the limitation of a test device, especially the change condition of the diffusion coefficient when the temperature changes. Therefore, a method for measuring diffusion coefficient under unsteady conditions is needed
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to overcome the defects in the prior art and provide an indoor test device for measuring the penetration diffusion of bentonite under the THMC coupling effect and a diffusion coefficient measuring method. The invention is used for carrying out a multi-field coupling influence test on the bentonite, particularly researching the influence of temperature change on the permeation and diffusion of the bentonite, and obtaining the permeation damage and diffusion breakdown mechanism of the bentonite. Meanwhile, the invention provides a method for monitoring and determining the diffusion coefficient in real time under the multi-field coupling working condition, can deeply research the diffusion breakdown mechanism in the process of the osmotic diffusion test, and has guiding significance on the seepage-proofing engineering of the refuse landfill.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
an indoor test device for measuring bentonite permeation and diffusion under THMC coupling effect comprises a pressure endowing device, a permeation and diffusion test device, a constant temperature control device and a test data processing device. The bentonite samples mentioned are referred to simply as bentonite.
Preferably, the pressure endowing device comprises a pneumatic maker, a pressure reducing valve, a pressure controller and a percolate replenishing tank; the pressure reducing valve converts the air pressure produced by the air pressure producing machine into water pressure through the pressure controller and the pressure controller, and the water pressure is sent into the percolate replenishing box; filtrate in the percolate supplementing box enters the infiltration cabin after being heated in the water bath heating box through the water inlet valve and the water inlet valve; the water bath heating box carries out water bath heating on the percolate in the percolation conduit and controls the temperature field of the solution entering the percolation cabin; the infiltration tank is in an infiltration diffusion test apparatus. The air pressure maker provides confining pressure and osmotic pressure required by an osmotic test, and the high pressure provided by the air pressure maker is reduced to a reasonable range by the pressure reducing valve and is accurately adjusted by the pressure controller. The device accurately provides stable water pressure for the osmotic diffusion test device, and meets the requirements of an osmotic flow field and a stress field in multi-field coupling through stable confining pressure while providing a hydraulic gradient required by the osmotic flow.
Preferably, the infiltration diffusion test device comprises an organic glass cylinder with an infiltration cabin inside, a constant temperature control device, a water inlet head water pipe, a water inlet valve, an infiltration flow guide pipe, an upper plate fixing bolt, a lower plate fixing bolt, a chassis support bolt, a bottom support supporting foot and an aluminum alloy support structure;
when leachate with certain temperature and water pressure passes through the seepage conduit, the leachate passes through the chassis with the through conduit and is communicated to the bottom plate with the groove in the process of reverse pressurization; after passing through the bottom plate with the groove, the soil particles are uniformly pressed on the lower permeable stone and then enter the bentonite through the filter paper for preventing the soil particles from entering the guide pipe; at the moment, the bentonite is tightly wrapped by the latex film and is subjected to uniform confining pressure in the infiltration cabin to carry out an infiltration diffusion test which meets the standard; then, the liquid in the percolate passes through a top cover with a through conduit and enters a tail liquid collecting and measuring box through a seepage conduit, and the conductivity of the percolate is measured in the tail liquid collecting and measuring box;
the organic glass cylinder comprises a penetration cabin, a top plate with a conduit and a bottom plate; the base plate and the top plate are tightly bolted by a nut through stainless steel materials and are sealed through an emulsion film, and a passage between the top plate and the base plate can only allow a seepage conduit or a lead with a specified radius to pass through, so that the tightness of the organic glass cylinder is ensured;
the infiltration cabin comprises a bottom cover, a lower permeable stone, bentonite, an upper permeable stone and a top cover with a permeable conduit, which are sequentially arranged from bottom to top; the equipment is wrapped by a latex film, and the latex film is tightly fixed between the upper top cover and the lower top cover, so that the latex film is prevented from sliding and the sample is prevented from leaking laterally under a confining pressure environment;
the top plate with the organic glass cylinder and the pipe capable of being communicated comprises a structure of a base plate, an upper plate fixing bolt, a lower plate fixing bolt, a base plate support bolt, a bottom support supporting leg and an aluminum alloy support; wherein, the top plate and the chassis are tightly fixed by the upper and lower plate fixing bolts through aluminum alloy support, and the chassis is supported by the chassis support bolts and the bottom support supporting feet to fix the organic glass cylinder.
After the pressure endowing device is opened, the valve of the permeation diffusion test device is opened, the pressure endowing device converts air pressure into stable water pressure, and the percolate in the percolate supplementing box is pressed into a water inlet head water pipe through the seepage guide pipe and then enters the organic glass cylinder with the permeation cabin inside through the opened water inlet valve. The percolate concentration in the percolate supplementing box is controlled, so that the influence of change of the percolate concentration is controlled, and the requirement of controlling a chemical field in multi-field coupling is met.
The mechanism of operation of the proposed osmotic diffusion test device is:
the percolate with certain temperature transmitted by the pressure endowing device passes through the guide pipe, passes through the chassis with the passable guide pipe and is communicated to the bottom plate with the groove. The solution with certain temperature and water pressure is evenly pressed on the permeable stone after passing through the bottom plate with the groove, and then enters the bentonite through the filter paper preventing the soil particles from entering the conduit. The bentonite was subjected to a pervaporation test during the reverse compression. After the leachate with a certain concentration enters the bentonite, the infiltration and diffusion actions are carried out. And finally, part of percolate enters a top cover with a passable conduit under the driving of hydraulic gradient and flows out of the infiltration diffusion test device.
The base plate and the top plate of the organic glass cylinder with the permeation cabin are tightly bolted by using a stainless steel material and nuts, and are sealed by a latex film, and a channel between the base plate and the top plate can only allow a guide pipe or a lead with a specified radius to pass through, so that the tightness of the organic glass cylinder is ensured. Simultaneously, the top plate and the base plate are tightly fixed through the aluminum alloy support by the upper plate fixing bolt and the lower plate fixing bolt, so that the organic glass cylinder is prevented from leaking under the confining pressure.
In the infiltration cabin mentioned to wrap up above-mentioned equipment with the emulsion membrane, adopt the inseparable fixed of rubber circle simultaneously between upper and lower top cap, prevent to enclose under the pressure environment that the emulsion membrane from sliding, lead to inside flexible wall sample to take place the edge leakage.
Preferably, the constant temperature control device comprises a water bath heating box, an electric heating rod and a constant temperature control panel; before entering an organic glass cylinder with a permeation cabin inside, the leachate firstly enters a water bath heating box; in a water bath heating box, heating the percolate, and entering an organic glass cylinder after reaching the specified temperature;
the electric heating rods are uniformly distributed along the organic glass cylinder, the percolate enters the infiltration cabin after passing through the water bath heating box, and the temperature of the infiltration cabin is changed according to different environmental temperatures; therefore, the internal temperature sensing piece is adopted to monitor the temperature of the solution in the tank in real time, and after the temperature is reduced to some extent, the constant-temperature control panel is adopted to heat a plurality of electric heating rods uniformly distributed along the organic glass cylinder, so that the temperature in the tank returns to the designated stability, and the requirement of a test temperature field is met.
Preferably, the test data processing device comprises a pre-buried film, a conductance integrated circuit, a conductance detection sheet, a tail liquid collecting and measuring box, a conductance detection centralized device and a post-processing computer; leachate flowing out of the permeation diffusion test device enters a tail liquid collecting and measuring box, and conductivity is measured through a conductivity detection centralized device;
the conductive detection sheets are arranged in a vertically staggered manner in a plurality of layers to meet the requirement of uniformly measuring soil bodies in different layers; the electric conduction detection sheet is positioned in the pre-buried film and is integrally regulated and controlled by the electric conduction integrated circuit; it should be noted that, in the measurement process, the conducting wire included in the conductive integrated circuit is required to be connected with a conductivity meter, and data is communicated to a computer to perform real-time calculation of the unsteady diffusion coefficient.
Preferably, leachate flowing out of the osmotic diffusion test device enters a tail liquid collecting and measuring box, and the conductivity is judged by the conductivity detection concentration device. At this time, the permeability coefficient under the non-steady state condition can be calculated by the formula (1):
wherein k is a permeability coefficient (m/s); a is the cross-sectional area (cm) of the seepage conduit2) (ii) a L is the thickness (cm) of the bentonite column; a is the cross-sectional area (cm) of the bentonite pattern2)；t1、t2The difference(s) between the starting time and the ending time of the test; h is1、h2Respectively at the start time t of the test1And a termination time t2The corresponding height (cm) of the water inlet pipe;
the diffusion coefficient under non-steady state conditions is expressed as formula (2):
in the formula, C is leachate concentration (mol/L); t is time(s); z is the diffusion depth (m); d0Is a diffusion systemNumber (m)2/s)；
However, in the permeation process, only the change value of the entire bentonite concentration with time can be obtained, and therefore, an accurate diffusion coefficient in the bentonite cannot be obtained.
Preferably, the test data processing device adopts a post-processing computer; the post-processing computer measures different detection sheets in different layers in different time periods; by means of measurement of subsection layering and time sharing, an unstable real-time diffusion coefficient is calculated by a post-processing computer;
calculating by a post-processing computer to obtain an unstable real-time diffusion coefficient, and determining the volume resistivity rho of the bentonite in an indoor test; calculating to obtain a diffusion coefficient through a known theoretical solution; and putting the pre-buried membrane into a permeation cabin, opening the conductivity detection sheets on the pre-buried membrane in a grouped, segmented and time-sharing manner, measuring the conductivity inside the soil body, and determining the instable real-time diffusion coefficient.
The invention discloses a method for measuring the diffusion coefficient of bentonite under THMC coupling, which adopts an indoor test device for measuring the permeation diffusion of the bentonite under the THMC coupling, and comprises the following steps:
step 1: measuring the volume resistivity rho of the bentonite column subjected to pre-hydration by adopting a Wenner probe method on the surface of the bentonite column by adopting leachate;
step 2: calculating by using a known theoretical solution to obtain a diffusion coefficient, testing and verifying the accuracy of the theoretical solution by using a reagent in a laboratory, and calculating by using a Nernet-Einstein equation;
and step 3: after the accuracy of the theoretical solution is verified through the steps, the pre-buried film is placed in a permeation cabin and tightly wrapped outside the bentonite and wrapped by the latex film, so that the path of conductivity measurement is only inside the bentonite soil body;
and 4, step 4: and connecting the pre-buried film with a conductivity detection concentration device through a conductivity integrated circuit, opening the detection sheets on the pre-buried film in a grouping and sectional manner, measuring the conductivity between the two points, and performing data post-processing by using a computer to obtain the instable real-time diffusion coefficient.
The invention provides a method for measuring the diffusion coefficient of a bentonite column, which aims to monitor and measure the diffusion coefficient in real time under a multi-field coupling working condition. The device comprises a tail liquid collecting and measuring box, a conductivity detection centralized device and a post-processing computer. The mentioned electric conduction pre-burying device comprises a pre-burying film containing a plurality of electric conduction probe needles. The electric conduction probe needles in the pre-buried film are divided into a plurality of rows which are arranged in a crossed manner. The device is connected with a conductivity meter through a lead, and data of the conductivity meter is communicated to a computer for instable real-time calculation.
It should be noted that the above description of the specific operation of the experiment is for the convenience of understanding and application of the ordinary skilled person, and it is obvious to those skilled in the art that the specific operation can be easily applied to other related cases after being subjected to simple revision. Therefore, the present invention is not limited to the specific operation description described above, and those skilled in the art should be able to make modifications and alterations to the specific operation in light of the principle of the present invention.
Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:
1. the penetration diffusion test device can meet the test control of a temperature field and a chemical field; the test data processing device comprises a conductance detection sheet, a tail liquid collecting and measuring box, a post-processing computer and the like;
2. after the conductivity of the bentonite is measured by the device in a sectional, layered and time-sharing manner, the diffusion coefficient in an unsteady state can be obtained by utilizing theoretical solution calculation, and the diffusion coefficient can be summarized and calculated after post-processing by a computer;
3. the invention carries out a multi-field coupling influence test on the bentonite, especially researches the influence of temperature change on the permeation and diffusion of the bentonite, and obtains the permeation damage and diffusion breakdown mechanism of the bentonite;
4. the method for monitoring and determining the diffusion coefficient in real time under the multi-field coupling working condition can deeply research the diffusion breakdown mechanism in the process of the permeation diffusion test and has guiding significance on the seepage-proofing engineering of the refuse landfill.
Drawings
FIG. 1 is a schematic view of a laboratory test apparatus according to the present invention.
Fig. 2 is a schematic view of a permeation capsule of the present invention.
FIG. 3 is a cross-sectional view of the constant temperature, diffusion coefficient measuring apparatus of the present invention.
FIG. 4 is a schematic view of the instrument for measuring diffusion coefficient of the present invention.
Fig. 5 is a schematic view of the pressure applying apparatus of the present invention.
FIG. 6 is a schematic view of a diffusion permeation test apparatus according to the present invention.
Fig. 7 is a schematic view of the thermostat control device of the present invention.
FIG. 8 is a schematic view of a test data processing apparatus according to the present invention.
In the figure, a top plate 1 with a through conduit, a top plate chassis 2 with a through conduit, an air pressure making machine 3, a pressure reducing valve 4, a pressure controller 51, a pressure controller 52, a percolate supplementing box 6, a water inlet head water pipe 71, a water inlet head water pipe 72, a water inlet valve 81, a water inlet valve 82, a water bath heating box 9, a top cover 10 with a through conduit, a bottom cover 11 with a groove, an organic glass cylinder 12, an upper permeable stone 131, an upper permeable stone 132, a latex film 14, a constant temperature control panel 15, uniformly arranged electric heating rods 16, an embedded film 17, a conductivity integrated circuit 18, a conductivity detection sheet 19, a conductivity detection and concentration device 20, a post-processing computer 21, a tail liquid collecting and measuring box 22, an upper and lower plate fixing bolt 23, a chassis support bolt 24, a bottom support foot 25, an aluminum alloy support 26, a seepage conduit 27, bentonite 28 and a permeation cabin 29.
Detailed Description
The bentonite is usually under the working condition of complex multi-field coupling effect in engineering, indoor tests are taken as a commonly used research method, a consolidometer is usually modified to perform permeation tests or a self-developed permeameter is used to perform the permeation tests in the current stage of research, few scholars combine the permeation tests and the diffusion tests to perform research, but the research in the current stage finds that a mutual feed mechanism is formed between the permeation coefficient and the diffusion coefficient, and a certain nonlinear relation exists, so that the simultaneous permeation and diffusion tests are very necessary.
Meanwhile, the current stage of tests mainly focuses on seepage, stress and Chemical single-field or multi-field research, and lacks of test equipment for measuring temperature-seepage-stress-Chemical (THMC) multi-field coupling, and can simultaneously perform seepage and diffusion tests. Meanwhile, in the current test method, there is a limitation in the diffusion coefficient determination under the unsteady state condition. In order to achieve the purpose, the solution proposed by the invention is as follows: an indoor test device for measuring the osmotic diffusion of bentonite under the THMC coupling effect comprises a pressure endowing device, an osmotic diffusion test device, a constant temperature control device and a test data processing device. The bentonite samples mentioned are referred to simply as bentonite.
The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:
the first embodiment is as follows:
in this embodiment, an indoor test device for measuring bentonite permeation and diffusion under THMC coupling effect includes a pressure applying device, a permeation and diffusion test device, a constant temperature control device, and a test data processing device.
In the present embodiment, the pressure imparting means includes the pneumatic maker 3, the pressure reducing valve 4, the pressure controller 51, the pressure controller 52, and the percolate replenishing tank 6; the pressure reducing valve 4 converts the air pressure produced by the air pressure maker 3 into water pressure through the pressure controller 51 and the pressure controller 52, and sends the water pressure into the percolate replenishing box 6; the filtrate in the percolate supplementing box 6 passes through a water inlet valve 81 and a water inlet valve 82 and enters the infiltration cabin after being heated in the water bath heating box 9; the water bath heating box 9 carries out water bath heating on the percolate in the seepage conduit 27 and controls the temperature field of the solution entering the seepage cabin; the infiltration tank is in an infiltration diffusion test apparatus.
In this embodiment, the infiltration diffusion test apparatus comprises a structure of an organic glass cylinder 12 with an infiltration chamber inside, a thermostatic control device, a water inlet head water pipe 71, a water inlet head water pipe 72, a water inlet valve 81, a water inlet valve 82, an infiltration conduit 27, an upper and lower plate fixing bolt 23, a chassis support bolt 24, a bottom support brace 25 and an aluminum alloy support 26;
when leachate with certain temperature and water pressure passes through the seepage conduit 27 and passes through the chassis 1 with the through conduit in the process of reverse pressure, the leachate is communicated to the bottom plate 11 with the groove; after passing through the grooved bottom plate 11, is uniformly pressed on the lower permeable stone 132, and then enters the bentonite through the filter paper preventing the soil particles from entering the guide tube; at the moment, the bentonite is tightly wrapped by the latex film 14 and is subjected to uniform confining pressure in the infiltration cabin to carry out an infiltration diffusion test meeting the standard; then, the liquid in the percolate passes through the top cover 10 with a pipe which can be communicated, enters the tail liquid collecting and measuring box 22 through the percolate guide pipe 27, and the conductivity of the percolate is measured in the tail liquid collecting and measuring box 22;
the organic glass cylinder 12 comprises a penetration cabin 29, a top plate 1 with a through conduit and a bottom plate 2; wherein, the base plate and the top plate are tightly bolted by a screw cap 23 by adopting a stainless steel material and are sealed by the latex film 14, and the passage of the top plate 1 and the base plate 2 only can lead a seepage conduit 27 or a lead with a specified radius to pass through, thereby ensuring the tightness of the organic glass cylinder 12;
the infiltration cabin 29 comprises a bottom cover 11, a lower permeable stone 132, bentonite 28, an upper permeable stone 131 and a top cover 10 with a through conduit which are sequentially arranged from bottom to top; the equipment is wrapped by the latex film 14, and the latex film 14 is tightly fixed between the upper top cover and the lower top cover, so that the latex film 14 is prevented from sliding and the sample is prevented from leaking laterally under the confining pressure environment;
the top plate 1 of the organic glass cylinder 12 with the pipe capable of being communicated comprises a structure of a bottom plate 2, an upper plate fixing bolt 23, a lower plate fixing bolt 23, a bottom plate support bolt 24, a bottom support supporting foot 25 and an aluminum alloy support 26; wherein, the top plate 1 and the chassis 2 are closely fixed by the upper and lower plate fixing bolts 23 through the aluminum alloy support 26, and the chassis support bolts 24 and the bottom support supporting feet 25 support the chassis 2 to fix the organic glass cylinder 12.
In the present embodiment, the thermostatic control device comprises a water bath heating box 9, an electric heating rod 16 and a thermostatic control panel 15; before entering the organic glass cylinder 12 with the infiltration cabin 29 inside, the percolate firstly enters a water bath heating box 9; in the water bath heating box 9, the percolate is heated and heated, and enters the organic glass cylinder 12 after reaching the specified temperature;
the electric heating rods 16 are uniformly distributed along the organic glass cylinder 12, and the percolate enters the infiltration cabin 29 after passing through the water bath heating box 9, so that the temperature of the infiltration cabin 29 is changed according to different environmental temperatures; therefore, the internal temperature sensing piece is adopted to monitor the temperature of the solution in the tank in real time, and after the temperature is reduced to some extent, the constant temperature control panel 15 is adopted to heat the plurality of electric heating rods 12 which are uniformly distributed along the organic glass cylinder, so that the temperature in the tank returns to the designated stability, and the requirement of a test temperature field is met.
In this embodiment, the test data processing device includes a pre-buried film 17, a conductance integrated circuit 18, a conductance probe sheet 19, a tail liquid collecting and measuring box 22, a conductance probe concentration device 20, and a post-processing computer 21; leachate flowing out of the permeation diffusion test device enters a tail liquid collecting and measuring box 22, and the conductivity is measured through a conductivity detection and concentration device 20;
the conductive detection sheets 19 are arranged in a vertically staggered manner in a plurality of layers to meet the requirement of uniformly measuring soil bodies in different layers; the conductance detection sheet 19 is positioned in the pre-buried film 17 and is integrally regulated and controlled by the conductance integrated circuit 18; it should be noted that during the measurement, the conductive wires included in the conductive integrated circuit 18 are required to be connected to the conductivity meter 20, and the data is transmitted to the computer for real-time calculation of the unsteady state diffusion coefficient.
In the present embodiment, the test data processing apparatus employs a post-processing computer 21; the post-processing computer 21 measures different detection slices in different layers at different time periods; by the measurement of subsection layering and time sharing, the post-processing computer 21 calculates to obtain the non-steady real-time diffusion coefficient;
the post-processing computer 21 calculates to obtain an unstable real-time diffusion coefficient, and the volume resistivity rho of the bentonite is determined in an indoor test; calculating to obtain a diffusion coefficient through a known theoretical solution; the pre-buried membrane 17 is placed in a permeation cabin, the conductivity detection sheets 19 on the pre-buried membrane 17 are opened in a grouping, subsection and time-sharing mode, the conductivity inside the soil body is measured, and the instable real-time diffusion coefficient is determined.
The penetration diffusion test device can meet the test control of a temperature field and a chemical field; the test data processing device comprises a conductance detection sheet, a tail liquid collecting and measuring box, a post-processing computer and the like; after the conductivity of the bentonite is measured by the device in the embodiment in a sectional, layered and time-sharing manner, the diffusion coefficient in an unsteady state can be obtained by utilizing theoretical solution calculation, and the diffusion coefficient can be summarized and calculated after post-processing by a computer; in the embodiment, a multi-field coupling influence test is carried out on the bentonite, particularly, the influence of temperature change on the permeation and diffusion of the bentonite is researched, and the permeation damage and diffusion breakdown mechanism of the bentonite is obtained;
example two:
this embodiment is substantially the same as the first embodiment, and is characterized in that:
in the present embodiment, as shown in fig. 1 and 5, the pressure-applying device includes a pneumatic pressure producing machine 3, a pressure reducing valve 4, a pressure controller 51, a pressure controller 52, and a percolate replenishing tank 6. The air pressure maker 3 supplies the confining pressure and the osmotic pressure required for the osmotic test, and the pressure reducing valve 4 reduces the high pressure supplied by the air pressure maker 3 to a reasonable range, typically 0-500kPa for the osmotic test. The pressure controller 51 converts the air pressure passing through the pressure reducing valve 4 into water pressure and precisely adjusts the water pressure, controls the water pressure within a test variable, and maintains the osmotic pressure during the osmosis process. The water pressure with a certain pressure intensity is sent into the percolate supplementing box 6, the percolate is sent into the water inlet head water pipe 71 and the water inlet head water pipe 72, and the water head height at the moment is recorded. Finally, the percolate passes through a water inlet valve 81 and a water inlet valve 82 respectively, is heated in the water bath heating box 9 and then enters the infiltration cabin 29.
In this embodiment, the water-bath heating box 9 can carry out the mode of water-bath heating to the filtration liquid through among the seepage flow pipe 27, heats filtration liquid, guarantees that filtration liquid is at the uniform temperature, satisfies the inside temperature of infiltration cabin 29 and reaches the experimental requirement.
In the present embodiment, the percolate supplementary tank 6 satisfies:
a. the percolate reaching the water inlet head water pipe 71 and the water inlet head water pipe 72 is the same percolate, and the concentration change of the percolate can be controlled;
b. in the subsequent infiltration diffusion test, if the percolate is insufficient, the percolate can be supplemented in time through a percolate supplementing box.
In this embodiment, as shown in fig. 2 and fig. 6, the mentioned infiltration diffusion test apparatus includes an infiltration chamber 29, an organic glass cylinder 12, a water inlet head pipe 71, a water inlet head pipe 72, a water inlet valve 81, a water inlet valve 82, an infiltration conduit 27, an upper and lower plate fixing bolt 23, a chassis support bolt 24, a bottom support brace 25, an aluminum alloy support 26, and the like.
In this embodiment, the mechanism of operation of the osmotic diffusion test apparatus is as follows: percolate at a certain temperature and water pressure passes through the chassis 1 with the through conduit and is communicated to the bottom plate 11 with the groove in the process of reverse pressure through the seepage conduit 27. After passing through the grooved bottom plate 11, is uniformly pressed against the lower permeable stone 132 and then through the filter paper that prevents soil particles from entering the conduit, into the bentonite 28. The bentonite 28 is tightly wrapped by the latex film 14 and subjected to a uniform confining pressure in the infiltration chamber 29, and an infiltration diffusion test meeting the standard is performed. The liquid in the percolate then passes through the top cover 10 with the accessible conduit and enters the tailings collection test chamber 22 via the percolate conduit 27, where the conductivity of the percolate is measured in the tailings collection test chamber 22.
In this example, the mentioned effects of measuring the conductivity of the exudate are:
1) the ratio of the conductivity of the exudate to the conductivity of the Exudate (EC) for the end of the penetration test conditions according to ASTM 6766out/ECin) When equal to 1.0 + -0.1, the test can be terminated;
2) judging whether the bentonite is broken down by the chemical ions in the leachate;
3) comparative analysis was performed with the diffusion coefficient determination data mentioned below.
In the present embodiment, the plexiglas cylinder 12 is mentioned to comprise a infiltration compartment 29, a top plate 1 with a passable duct and a bottom plate 2. Wherein, adopt stainless steel material to closely bolt with nut 23 between chassis and the overhead pan, seal through emulsion membrane 14, the passageway of overhead pan 1 and chassis 2 only can make the seepage flow pipe 27 or the wire of appointed radius pass through, guarantees the leakproofness of organic glass section of thick bamboo 12.
In the present embodiment, the mentioned infiltration compartments 29 are arranged in the following order from bottom to top: a bottom cover 11 with grooves, a lower permeable stone 132, filter paper, bentonite 28, an upper permeable stone 13 and a top cover 10 with a conduit. And the latex film 14 wraps the equipment, and the latex film 14 is tightly fixed between the upper top cover and the lower top cover, so that the latex film 14 is prevented from sliding and the sample is prevented from leaking laterally under the confining pressure environment.
In the embodiment, the top plate 1 with the through conduit of the organic glass cylinder 12 comprises a bottom plate 2, an upper plate fixing bolt 23, a lower plate fixing bolt 24, a bottom plate support bolt 25, an aluminum alloy support 26 and the like. Wherein, go up lower plate fixing bolt 23 with top dish 1 and chassis 2 support 26 through the aluminum alloy and carry out inseparable fixed, guarantee that a organic glass section of thick bamboo 12 does not take place the seepage under the circumstances of confined pressure. The chassis 2 is supported by the chassis support bolts 24 and the bottom support feet 25 and acts to secure the plexiglas cylinder 12.
In the present embodiment, as shown in fig. 7, the mentioned thermostatic control device comprises a water bath heating box 9, an electric heating rod 16 and a thermostatic control panel 15. The percolate first enters a water bath heating box 9 before entering the plexiglass cartridge 12 with the infiltration compartment 29 inside. In the water bath heating box 9, the percolate is heated and heated up, and enters the organic glass cylinder 12 after reaching the specified temperature.
In the present embodiment, the mentioned electric heating rod 16 includes a plurality of temperature sensing pieces uniformly arranged along the plexiglass cylinder 12, as shown in fig. 3. The percolate enters the infiltration tank 29 after passing through the water bath heating box 9, but due to the difference of the ambient temperature, the temperature of the infiltration tank 29 changes. Therefore, the internal temperature sensing piece is adopted to monitor the temperature of the solution in the tank in real time, and after the temperature is reduced to some extent, the constant temperature control panel 15 is adopted to heat the plurality of electric heating rods 12 which are uniformly distributed along the organic glass cylinder, so that the temperature in the tank returns to the designated stability, and the requirement of a test temperature field is met.
In the present embodiment, the measured permeability coefficient is generally calculated by a method in which the permeability coefficient is proportional to the logarithm of the head height ratio, as shown in formula (1). Therefore, the water head height difference between the water inlet head pipe 71 and the water inlet head pipe 72 within a certain time is recorded, and the experimental value of the permeability coefficient is calculated.
Wherein k is a permeability coefficient (m/s); a is the cross-sectional area (cm) of the seepage conduit2) (ii) a L is the thickness (cm) of the bentonite column; a is the cross-sectional area (cm) of the bentonite pattern2)；t1、t2The difference(s) between the starting time and the ending time of the test; h is1、h2Respectively at the start time t of the test1And a termination time t2The corresponding height (cm) of the water inlet pipe.
As shown in fig. 1 and 7, the test data processing device includes a pre-buried film 17, a conductance integrated circuit 18, a conductance probe sheet 19, a tail liquid collecting and measuring box 22, a conductance probe centralized device 20, and a post-processing computer 21. Leachate from the pervaporation device will enter the tailings collection test chamber 22 where conductivity is measured by the conductivity probe concentrator 20.
In this example, a method of determining the diffusion coefficient. The specific method comprises the following steps:
in this embodiment, as shown in fig. 5, the conductive detection sheets 19 are arranged in a staggered manner from top to bottom in several layers, so as to meet the requirement of uniformly measuring soil bodies in different layers. The electric conduction detection sheet 19 is positioned in the pre-buried film 17 and is integrally regulated and controlled by the electric conduction integrated circuit 18. It should be noted that, in the measurement process, the conducting wire included in the conductance integrated circuit 18 is required to be connected with a conductance meter, and the data of the conductance meter is communicated to a computer, so that the unsteady state diffusion coefficient is calculated in real time by a method for acquiring the diffusion coefficient.
In the present embodiment, the mentioned method for obtaining the diffusion coefficient includes an experimental method and an analytical method. Besides measuring the diffusion coefficient by common test methods such as a diffusion column and a diffusion channel method, an analytic solution can be obtained according to Fick's second law (equation (2)):
in the formula, C is leachate concentration (mol/L); t is time(s); z is the diffusion depth (m); d0Is the diffusion coefficient (m)2/s)。
In the present embodiment, the mentioned post-processing computer 21 performs measurements of different detection patches in different layers at different time periods. By means of the measurement of sectional layering and time sharing, the post-processing computer 21 calculates the non-steady real-time diffusion coefficient.
The method comprises the following specific steps:
step 1: in an indoor test, a Wenner probe method is adopted to test the surface of a bentonite column hydrated with leachate in advance by using a probe, and the volume resistivity rho of the bentonite is measured when the bentonite adsorbs the leachate on the surface.
Step 2: and calculating to obtain the diffusion coefficient by adopting a known theoretical solution, measuring the experimental diffusion coefficient by a laboratory reagent method, and comparing and analyzing the obtained theoretical solution to obtain the accuracy. The method adopts a Nernet-Einstein equation to calculate:
wherein D is the diffusion coefficient (m) of the sample2S); r is the gas constant (J/(K.mol)); t is the absolute temperature (K); z is the number of charges or the number of valence bits; f is a Phillips constant, and 96500C/mol is taken; t is the ion transport number; c is ion concentration (mol/L); rho is the volume resistivity obtained by the Wenner probe method; γ is the activity coefficient of the ion, typically 1.
And step 3: after the accuracy of theoretical solution is verified through the steps, the pre-buried membrane is placed in the infiltration cabin 29 and tightly wrapped outside the bentonite 28 and wrapped by the latex membrane 14, so that the path of conductivity measurement is only carried out inside the soil body, and the latex membrane carries out insulation treatment on internal and external percolate, thereby ensuring the accuracy of test measurement.
And 4, step 4: the pre-buried film is connected with a conductivity detection concentration device 20 through a conductivity integrated circuit 18, the conductivity detection sheets 19 on the pre-buried film 17 are opened in a grouped, segmented and time-sharing mode, after the conductivity between two points of an interval soil body is measured, a post-processing computer 21 is used for carrying out data post-processing, and the instable real-time diffusion coefficient is obtained.
This example is an indoor test apparatus for measuring bentonite permeation diffusion under THMC coupling and a method for measuring diffusion coefficient; the pressure endowing device comprises an air pressure manufacturing machine, a pressure reducing valve, a pressure controller, a percolate supplementing box and the like, and can meet the test control on a seepage field and a stress field; the infiltration diffusion test device mainly comprises an organic glass cylinder with an infiltration cabin inside, a constant temperature control device, a water inlet head water pipe and other structures, and can meet the test control of a temperature field and a chemical field; the test data processing device comprises a conductance detection sheet, a tail liquid collecting and measuring box, a post-processing computer and the like. Meanwhile, the method for measuring the diffusion coefficient is described in this example. After the conductivity of the bentonite is measured by the device in a sectional, layered and time-sharing manner, the diffusion coefficient in an unsteady state can be obtained by utilizing theoretical solution calculation, and the diffusion coefficient can be summarized and calculated after post-processing by a computer.
The embodiments of the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the embodiments, and various changes and modifications can be made according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention shall be equivalent substitutions, as long as the purpose of the present invention is met, and the present invention shall fall within the protection scope of the present invention without departing from the technical principle and inventive concept of the present invention.
Claims (7)
1. The utility model provides a survey bentonite infiltration diffusion's indoor test device under THMC coupling effect which characterized in that: the test device comprises a pressure endowing device, a penetration diffusion test device, a constant temperature control device and a test data processing device.
2. The laboratory test apparatus for measuring the bentonite permeation and diffusion under the THMC coupling effect according to claim 1, which is characterized in that: the pressure endowing device comprises a pneumatic making machine (3), a pressure reducing valve (4), a pressure controller (51), a pressure controller (52) and a percolate supplementing box (6); the pressure reducing valve (4) converts the air pressure produced by the air pressure producing machine (3) into water pressure through a pressure controller (51) and a pressure controller (52), and the water pressure is sent into a percolate replenishing box (6); filtrate in the percolate supplementing box (6) passes through a water inlet valve (81) and a water inlet valve (82) and enters the infiltration cabin after being heated in a water bath heating box (9); the water bath heating box (9) carries out water bath heating on the percolate in the seepage conduit (27) and controls the temperature field of the solution entering the seepage cabin; the infiltration tank is in an infiltration diffusion test apparatus.
3. The laboratory test apparatus for measuring the bentonite permeation and diffusion under the THMC coupling effect according to claim 1, which is characterized in that: the infiltration diffusion test device comprises a structure of an organic glass cylinder (12) with an infiltration cabin inside, a constant temperature control device, a water inlet head water pipe (71), a water inlet head water pipe (72), a water inlet valve (81), a water inlet valve (82), an infiltration guide pipe (27), an upper disc fixing bolt and a lower disc fixing bolt (23), a chassis support bolt (24), a bottom support supporting foot (25) and an aluminum alloy support (26);
when leachate with certain temperature and water pressure passes through the seepage conduit (27) and passes through the chassis (1) with the through conduit in the process of reverse pressure, the leachate is communicated to the bottom plate (11) with the groove; after passing through the grooved bottom plate (11), is uniformly pressed on the lower permeable stone (132) and then enters the bentonite through the filter paper preventing the soil particles from entering the conduit; at the moment, the bentonite is tightly wrapped by the latex film (14) and is subjected to uniform confining pressure in the infiltration cabin to carry out an infiltration diffusion test meeting the standard; then, the liquid in the percolate passes through a top cover (10) with a through conduit and enters a tail liquid collecting and measuring box (22) through a seepage conduit (27), and the conductivity of the percolate is measured in the tail liquid collecting and measuring box (22);
the organic glass cylinder (12) comprises a penetration cabin (29), a top plate (1) with a through conduit and a bottom plate (2); the base plate and the top plate are tightly bolted by a screw cap (23) by adopting a stainless steel material and are sealed by a latex film (14), and a passage between the top plate (1) and the base plate (2) only can allow a seepage conduit (27) or a lead with a specified radius to pass through, so that the tightness of the organic glass cylinder (12) is ensured;
the infiltration cabin (29) comprises a bottom cover (11), a lower permeable stone (132), bentonite (28), an upper permeable stone (131) and a top cover (10) with a permeable pipe, which are sequentially arranged from bottom to top; the equipment is wrapped by a latex film (14), and the latex film (14) is tightly fixed between the upper top cover and the lower top cover, so that the latex film (14) is prevented from sliding and the sample is prevented from leaking laterally under the confining pressure environment;
the top plate (1) of the organic glass cylinder (12) with the pipe capable of being communicated comprises a base plate (2), an upper plate fixing bolt (23), a lower plate fixing bolt (23), a base plate support bolt (24), a bottom support supporting foot (25) and an aluminum alloy support (26); wherein, go up lower plate fixing bolt (23) and carry out inseparable fixed with top dish (1) and chassis (2) through aluminum alloy support (26), chassis support bolt (24), bottom support arm brace (25) have supported chassis (2), fixed organic glass section of thick bamboo (12).
4. The indoor test device for measuring the penetration and diffusion of the bentonite under the THMC coupling effect according to claim 1, is characterized in that: the constant temperature control device comprises a water bath heating box (9), an electric heating rod (16) and a constant temperature control panel (15); before entering an organic glass cylinder (12) with a penetration cabin (29) inside, the percolate firstly enters a water bath heating box (9); in a water bath heating box (9), the percolate is heated and heated, and enters an organic glass cylinder (12) after reaching the specified temperature;
the electric heating rods (16) are uniformly distributed along the organic glass cylinder (12), and the percolate passes through the water bath heating box (9) and then enters the infiltration cabin (29), so that the temperature of the infiltration cabin (29) is changed according to different environmental temperatures; therefore, the solution temperature in the cabin is monitored in real time by the internal temperature sensing piece, and after the temperature is reduced to some extent, the constant temperature control panel (15) is used for heating a plurality of electric heating rods (12) which are uniformly distributed along the organic glass cylinder, so that the temperature in the cabin returns to the designated stability, and the requirement of a test temperature field is met.
5. The laboratory test apparatus for measuring the bentonite permeation and diffusion under the THMC coupling effect according to claim 1, which is characterized in that: the test data processing device comprises a pre-buried film (17), a conductance integrated circuit (18), a conductance detection sheet (19), a tail liquid collecting and measuring box (22), a conductance detection centralized device (20) and a post-processing computer (21); leachate flowing out of the permeation diffusion test device enters a tail liquid collecting and measuring box (22), and conductivity is measured through a conductivity detection centralized device (20);
the conductive detection sheets (19) are arranged in a vertically staggered manner in a plurality of layers to meet the requirement of uniformly measuring soil bodies in different layers; the electric conduction detection sheet (19) is positioned inside the pre-buried film (17) and is integrally regulated and controlled by an electric conduction integrated circuit (18); it should be noted that during the measurement, the conducting wires contained in the conductive integrated circuit (18) are required to be connected with the conductivity meter (20), and data is transmitted to the computer to perform the real-time calculation of the unsteady diffusion coefficient.
6. The laboratory test apparatus for measuring the bentonite permeation and diffusion under the THMC coupling effect according to claim 1, which is characterized in that: the test data processing device adopts a post-processing computer (21); a post-processing computer (21) measures different detection slices in different layers at different time periods; by means of measurement of subsection layering and time sharing, an unstable real-time diffusion coefficient is obtained through calculation of a post-processing computer (21);
a post-processing computer (21) calculates to obtain an unstable real-time diffusion coefficient, and the volume resistivity rho of the bentonite is determined in an indoor test; calculating to obtain a diffusion coefficient through a known theoretical solution; the pre-buried membrane (17) is placed in a permeation cabin, the conductivity detection sheets (19) on the pre-buried membrane (17) are opened in a grouping, subsection and time-sharing mode, the conductivity inside the soil body is measured, and the instable real-time diffusion coefficient is determined.
7. A method for measuring the diffusion coefficient of bentonite under THMC coupling action, which adopts the indoor test device for measuring the bentonite permeation diffusion under THMC coupling action as claimed in claim 1, and is characterized by comprising the following steps:
step 1: measuring the volume resistivity rho of the bentonite column subjected to pre-hydration by adopting a Wenner probe method on the surface of the bentonite column by adopting leachate;
step 2: calculating by using a known theoretical solution to obtain a diffusion coefficient, testing and verifying the accuracy of the theoretical solution by using a reagent in a laboratory, and calculating by using a Nernet-Einstein equation;
and step 3: after the accuracy of the theoretical solution is verified through the steps, the pre-buried film is placed in a permeation cabin and tightly wrapped outside the bentonite and wrapped by the latex film, so that the path of conductivity measurement is only inside the bentonite soil body;
and 4, step 4: and connecting the pre-buried film with a conductivity detection concentration device through a conductivity integrated circuit, opening the detection sheets on the pre-buried film in a grouping and sectional manner, measuring the conductivity between the two points, and performing data post-processing by using a computer to obtain the instable real-time diffusion coefficient.
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