CN115791531A - A device and method for simulating grouting in loose leakage formations - Google Patents

Abstract

The invention discloses a loose and lost stratum grouting simulation device and method, which comprises a circulating grouting system, a plugging efficiency evaluation system and a data acquisition system, wherein the circulating grouting system comprises a circulating grouting system, a plugging efficiency evaluation system and a data acquisition system; the circulating grouting system comprises a slurry storage tank, a first slurry inlet pipe with a slurry stop valve, a grouting pump, a second slurry inlet pipe, a buffer tank, a third slurry inlet pipe, a sample cylinder and a slurry outlet pipe; the plugging efficiency evaluation system comprises a first flow meter, a second pressure meter, a first slurry stop valve, a sample cylinder, a third pressure meter and a second slurry stop valve; the data acquisition system comprises a first pressure gauge, a first digital camera, an image acquisition computer, a second digital camera and a fourth pressure gauge. The invention can simulate the grouting process of a loose and lost stratum and realize quantitative and qualitative evaluation on the grouting effect through the plugging efficiency evaluation system and the data acquisition system. The simulation of the whole grouting process of the unconsolidated and lost stratum is realized, and conditions are created for the selection of grouting materials, the optimization design of formula performance parameters and grouting technological parameters.

Description

A device and method for simulating grouting in loose leakage formations

technical field

The invention relates to a grouting simulation device and method for a loose leakage formation, belonging to the field of grouting simulation tests.

Background technique

In the field of geotechnical grouting engineering, loose and lost formations are often encountered, such as fault fracture zones and elevated formations accumulated in front of slopes. The grouting here is faced with a large amount of grout leakage, high environmental hazards, and it is difficult to meet the requirements of engineering design for benefits and construction period. In addition, the phenomenon that the grout is completely lost and it is difficult to return to the grout often occurs (such as grouting in anchoring projects, etc.), which brings great challenges to geotechnical grouting projects. Therefore, there is an urgent need for effective technical means to assist in solving the above engineering problems.

At present, physical model tests are widely used to obtain grouting parameters. According to the Chinese patent document with the publication number CN113063701A and the publication date of July 02, 2021, a visual grouting simulation device and method for saturated sandy soil strata are disclosed, which are characterized in that: it includes a receptacle container and is filled in the receptacle container The transparent sand medium inside, the injector container is made of transparent materials, the transparent sand medium is composed of marine babies after absorbing water and swelling according to the preset gradation, the injector container is connected with the grouting system, the confining pressure system and a water pressure control system, the grouting system injects grout into the transparent sand medium, the confining pressure system realizes confining pressure loading on the transparent sand medium, and the water pressure control system injects grout into the transparent sand medium. The sand medium provides groundwater and controls water pressure. The visual grouting simulation device for saturated sandy soil strata also includes a monitoring system, which monitors grouting parameters and collects and stores image data. The grouting effect under the grouting parameters is visually evaluated.

However, for loose formations, the actual engineering problems are mainly concentrated in the large amount of slurry loss. Therefore, it is particularly important to evaluate the leakage characteristics of slurry in loose formations and the plugging process of seepage channels. However, as far as the existing grouting simulation devices are concerned, it is not yet possible to effectively simulate the grouting process for loose leakage formations.

Contents of the invention

In order to realize the simulation of the grouting process of the loose leakage formation, the present invention aims at the defects of the prior art, explores the leakage characteristics of the grout and the channel blocking process, and performs grouting material selection and grouting parameter control accordingly. The present invention provides a loose A leaky formation grouting simulation device and method.

The technical solution provided by the present invention to solve the above technical problems is: a loose leakage formation grouting simulation device, including a circulating grouting system, a plugging efficiency evaluation system and a data acquisition system, and the circulating grouting system includes a grout storage tank, The first slurry inlet pipe with a slurry stop valve, the grouting pump, the second slurry inlet pipe, the buffer tank, the third slurry inlet pipe and the slurry outlet pipe; the plugging efficiency evaluation system includes a first flow rate meter, a second flow rate meter, the second pressure gauge, the first slurry stop valve, the sample cylinder, the third pressure gauge and the second slurry stop valve; the data acquisition system includes the first pressure gauge, the first digital camera, the image acquisition computer, the second Digital camera, fourth pressure gauge;

The upper part of the grout storage tank is communicated with the upper part of the sample cylinder through the grout outlet pipe, and the bottom is communicated with the input end of the grout pump through the first grout inlet pipe; the output end of the grout pump is connected with the sample cylinder through the second grout inlet pipe The lower part of the buffer tank is communicated; the upper part of the buffer tank is communicated with the bottom of the sample cylinder through the third slurry inlet pipe;

Both the second flow meter and the fourth pressure gauge are installed on the slurry outlet pipe; the third pressure gauge, the second slurry stop valve, the second pressure gauge, and the first slurry stop valve are all installed on the sample cylinder; Both the first flow meter and the first pressure gauge are installed on the third slurry inlet pipe;

The image acquisition computer is electrically connected to the first digital camera and the second digital camera respectively; the first digital camera is facing the fourth pressure gauge, and the second digital camera is facing the first pressure gauge.

A further technical solution is that the slurry storage tank includes a cylinder with a flange, a steel frame of the slurry storage tank, a top cover, a motor, a stirring shaft and a bottom cover with a round hole for the slurry, and the first slurry inlet pipe It communicates with the pulp outlet hole, the top cover and the bottom cover are respectively connected to the upper and lower ends of the cylinder, the bottom cover is installed on the steel frame of the slurry storage tank, the motor is installed on the top cover, and the top cover There is a round hole in the center, and the upper end of the stirring shaft passes through the round hole and is connected with the rotating shaft of the motor. There is a through hole in the upper right side of the cylinder with a flange, and the pulp outlet pipe is connected with the The slurry inlet hole is connected.

A further technical solution is that three layers of sealing rings are installed between the cylinder and the bottom cover.

A further technical solution is that the sample cylinder includes a sample cylinder with a flange, a top cover of the sample cylinder, a steel frame of the sample cylinder, and a bottom cover of the sample cylinder with a round hole for feeding the sample. The top cover of the sample tube and the bottom cover of the sample tube are respectively installed on the upper and lower ends of the sample tube cylinder, the bottom cover of the sample tube is installed on the steel frame of the sample tube, and the third slurry inlet pipe is connected with the test tube. The sample inlet is connected to the slurry circle; the upper left side wall of the sample cylinder is provided with a through sample slurry outlet hole, and the slurry outlet tube is connected to the sample slurry outlet hole.

A further technical solution is that sealing rings are installed between the sample cylinder cylinder, the top cover of the sample cylinder, and the bottom cover of the sample cylinder.

A further technical solution is that two through threaded holes are formed on the side wall of the sample cylinder, and the first slurry stop valve and the second slurry stop valve are threadedly connected with the two through thread holes respectively.

A further technical solution is that the free ends of the first slurry stop valve and the second slurry stop valve are respectively installed with a second pressure gauge and a third pressure gauge in a threaded connection, which are used to measure the water head of the upper and lower flow sections of the injected medium. Difference.

A further technical solution is that the first flow meter and the first pressure gauge are installed on the third slurry inlet pipe by thread connection; the second flow meter and the fourth pressure gauge are both installed on the slurry outlet pipe by thread connection superior.

A method for simulating grouting in loose leakage formations, which can realize quantitative and qualitative evaluations of grouting effects, and the quantitative evaluation specifically includes the following steps:

Step 1. Fill the sample cylinder with the pebbles and gravels selected in the test to simulate the loose leakage formation;

Step 2, close the slurry stop valve of the first slurry inlet pipe, and add water into the slurry storage tank;

Step 3. Open the first grout stop valve and the second grout stop valve, simultaneously open the grout stop valve of the first grout inlet pipe, and start the grouting pump;

Step 4. After the water flow rate is stable, read the flow rate Q from the first flow meter, read the water pressure P ₁ from the second pressure gauge, and read the water pressure P ₂ from the third pressure gauge;

Step 5, adopt the following formula to calculate the initial permeability coefficient K _in of the simulated formation:

In the formula: L is the vertical center distance between the second pressure gauge and the third pressure gauge, in cm, F is the internal cross-sectional area of the sample cylinder, in cm ² ; Q is the flow rate read by the first flow meter, in cm cm ³ /s; P ₁ is the water pressure read by the second pressure gauge, in kPa; P ₂ is the water pressure read by the third pressure gauge, in kPa;

Step 6. Record the initial permeability coefficient, discharge the circulating water in the device, and close the slurry stop valve of the first slurry inlet pipe;

Step 7. Weigh the selected grouting formula according to the amount, add it to the slurry storage tank, and start the mixer to mix the slurry until uniform;

Step 8. Close the first grout stop valve and the second grout stop valve, open the grout stop valve of the first grout inlet pipe, and start the grouting pump;

Step 9. Circulate the grouting to the design time, turn off the grouting pump, remove the sample cylinder and remove the bottom cover of the sample cylinder, and let the excess slurry in the sample cylinder Free flow under the action of self-gravity;

Step 10. After the residual slurry in the sample cylinder is consolidated and hardened, reassemble the sample cylinder to the simulation device, and use the method described in steps 1-5 to measure and calculate the termination permeability coefficient K _fi ;

Step 11. According to the initial permeability coefficient K _in and the final permeability coefficient K _fi of the sample, calculate the grouting plugging efficiency η as follows:

In the formula: K _in is the initial permeability coefficient of the sample; K _fi is the final permeability coefficient; η is the plugging efficiency of grouting.

A method for simulating grouting in loose leakage formations, which can realize quantitative and qualitative evaluations of grouting effects, and the qualitative evaluation of grouting effects specifically includes the following steps:

Step 1. Fill the sample cylinder with the pebbles and gravels selected in the test to simulate the loose leakage formation;

Step 2. Close the grout stop valve of the first grout inlet pipe, weigh the selected grouting formula according to the amount, add it to the grout storage tank, and turn on the mixer to mix the grout until uniform;

Step 3. Close the first grout stop valve and the second grout stop valve, open the grout stop valve of the first grout inlet pipe, and start the grouting pump;

Step 4, using the data acquisition system to record the readings of the first pressure gauge and the second pressure gauge once per minute, and the data is drawn by computer, so as to qualitatively analyze the leakage characteristics of the slurry and the sealing state of the formation;

Step 5. After the test is completed, turn off the power of the device, disconnect the detachable connection, and clean the device by module.

The present invention has the following beneficial effects:

1. The size of the sample cylinder according to the present invention can be changed according to the specific test requirements, and the particle size and gradation of the filled pebbles and gravels can also be designed according to the actual simulation objects, which can meet the grouting simulation under many working conditions;

2. The device of the present invention can realize the systematic evaluation of the grouting effect on the loose leakage formation from qualitative and quantitative perspectives, and from the quantitative perspective, the plugging efficiency evaluation system can be used to calculate the plugging efficiency of the loose leakage medium at different times of grouting ;From a qualitative point of view, the pressure change during the grouting process can be monitored through the data acquisition system, so as to analyze the permeability characteristics of the grout and the plugging of the simulated medium;

3. According to the evaluation result of the grouting effect of the device of the present invention, the adaptability difference of different grouting materials to the injected medium can be compared, so as to optimize the grouting material, and also provide information for the design of formula parameters and grouting parameters. Strong support.

Description of drawings

Fig. 1 is the overall structure and connection schematic diagram of the present invention;

Fig. 2 is the result of qualitative analysis of two kinds of grouting materials for plugging loose leakage medium in Example 3 of the present invention.

As shown in the figure: 1 is the motor; 2 is the top cover; 3 is the second flow meter; 4 is the fourth pressure gauge; 5 is the second digital camera; 6 is the image acquisition computer; A digital camera; 9 is the top cover of the sample tube; 10 is the second check valve; 11 is the third pressure gauge; 12 is the cylinder of the sample tube; 13 is the first check valve; 14 is the second pressure gauge; 15 is the bottom cover of the sample cylinder; 16 is the steel frame of the sample cylinder; 17 is the third slurry inlet pipe; 18 is the first pressure gauge; 19 is the first flow rate meter; 20 is the buffer tank; 21 is the second slurry inlet pipe ; 22 is the grouting pump; 23 is the first slurry inlet pipe; 24 is the steel frame of the slurry tank; 25 is the bottom cover; 26 is the cylinder.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Apparently, the described embodiments are some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

As shown in Figure 1, a loose leakage formation grouting simulation device of the present invention includes a circulating grouting system, a plugging efficiency evaluation system and a data acquisition system.

The circulating grouting system includes a grout storage tank, a first grout inlet pipe 23 with a grout stop valve, a grout pump 22, a second grout inlet pipe 21, a buffer tank 20, a third grout inlet pipe 17, a sample cylinder and The slurry outlet pipe 7 is formed;

Wherein, the material of the slurry storage tank is plexiglass, including a cylinder 26 with a flange, a top cover 2, a stirring shaft, a steel frame of the slurry storage tank 24, a motor 1 and a bottom cover 25 with a round hole for discharging slurry. The bottom cover 25 is installed on the steel frame 24 of the slurry storage tank, the cylinder 26, the top cover 2 and the bottom cover 25 are all connected by bolts, and three layers of sealing rings are installed between the cylinder 26 and the bottom cover 25 ; The upper right side wall of the cylinder 26 with a flange has a through hole for feeding the slurry; the motor 1 is installed on the top cover 2, and the center of the top cover 2 has a round hole, and the stirring shaft passes through the After the round hole is connected with the rotating shaft of the motor 1;

Wherein, the material of the sample tube is plexiglass, including a sample tube cylinder 12 with a flange, a sample tube top cover 9, a sample tube steel frame 16, and a sample tube with a sample slurry inlet hole. Bottom cover 15, the sample tube bottom cover 15 is installed on the sample tube steel frame 16, the sample tube cylinder 12, the sample tube top cover 9 and the sample tube bottom cover 15 are connected by bolts, And there are sealing rings installed between the sample tube cylinder 12, the sample tube top cover 9 and the sample tube bottom cover 15; the sample tube can be filled with loose injected medium, and the sample tube cylinder 12 upper left side The wall is provided with a through sample slurry outlet hole, and the middle and side walls are provided with two through threaded holes, and the first slurry stop valve 13 and the second slurry stop valve 10 are threadedly connected with the two threaded holes respectively.

The specific installation sequence and method of each part of the circulating grouting system are as follows: the left end of the first grouting pipe 23 is bonded to the grouting hole of the bottom cover 25, and the right end is screwed to the input end of the grouting pump 22; The left end of the pipe 21 is threadedly connected to the output end of the grouting pump 22, and the right end is detachably connected to the grouting port of the buffer tank 20 to ease the grouting pressure; the left end of the third grouting pipe 17 is connected to the grouting port of the buffer tank 20 Detachable connection, the right end is bonded to the sample slurry inlet hole of the sample cylinder bottom cover 15; the left end of the slurry outlet pipe 7 is detachably connected to the slurry inlet hole on the upper right side wall of the cylinder 26, and the right end is connected to the sample cylinder The sample slurry outlet hole on the upper left side wall of the cylinder 12 is detachably connected. After the installation is completed, the grouting pump 22 provides grouting power to realize circulating grouting. In this embodiment, the flow rate adjustment range of the grouting pump 22 is 4300-12000L/h, and different gears can be selected according to different grouting requirements .

The plugging efficiency evaluation system includes a first flow meter 19 , a second flow meter 3 , a second pressure gauge 14 , a first slurry stop valve 13 , a sample cylinder, a third pressure gauge 11 and a second slurry stop valve 10 . Wherein, the first flow meter 19 is installed on the third slurry inlet pipe 17 by threaded connection; the second pressure gauge 14 and the third pressure gauge 11 are installed on the first slurry stop valve 13 and the third slurry valve by threaded connection respectively. Two free ends of the slurry stop valve 10 are used to measure the water head difference of the upper and lower flow sections of the injected medium. The plugging efficiency evaluation system can calculate the plugging efficiency based on Darcy's law of seepage, and realize the quantitative evaluation of the grouting effect.

The data acquisition system includes a first pressure gauge 18 , a first digital camera 8 , an image acquisition computer 6 , a second digital camera 5 and a fourth pressure gauge 4 . Wherein, the first pressure gauge 18 and the first flow meter 19 are installed on the pulp outlet pipe 7 by screw connection; the image acquisition computer 6 is electrically connected with the first digital camera 8 and the second digital camera 5 respectively. The first digital camera 8 is facing the fourth pressure gauge 4 , and the second digital camera 5 is facing the first pressure gauge 18 . The data acquisition system mainly monitors the grouting pressure during the cyclic grouting process through a digital camera, stores the image data in the computer, and finally makes a map of the grouting pressure change process for qualitative evaluation of the grouting effect.

Example 2

Embodiment 2 of the present invention provides a method for quantitative evaluation of grouting simulation in loose leakage formations, which is matched with the device provided in Embodiment 1, and specifically includes the following steps:

Step 1. Fill the sample cylinder with pebbles and gravels with a particle size of 20-40mm selected in the test to simulate loose leakage formations;

Step 2, close the slurry stop valve of the first slurry inlet pipe 23, and add water into the slurry storage tank;

Step 3. Open the first grout stop valve 13 and the second grout stop valve 10, open the grout stop valve of the first grout inlet pipe 23, and start the grout pump;

Step 4. After the water flow rate is stable, read the flow rate Q from the first flow meter ₁₉ , read the water pressure P1 from the second pressure gauge 14, and read the water pressure P2 from the third pressure gauge ₁₁ ;

Step 5, adopt the following calculation formula to calculate the initial permeability coefficient K _in of the simulated formation;

In the formula: L is the vertical center distance between the second pressure gauge and the third pressure gauge, in cm, F is the internal cross-sectional area of the sample cylinder, in cm ² ; Q is the flow rate read by the first flow meter, in cm cm ³ /s; P ₁ is the water pressure read by the second pressure gauge, in kPa; P ₂ is the water pressure read by the third pressure gauge, in kPa;

Step 6, record the initial permeability coefficient, discharge the circulating water in the device, and close the slurry stop valve of the first slurry inlet pipe 23;

Step 7. Weigh the selected quick-setting grouting formula according to the amount, add it to the slurry storage tank, and start the mixer to mix the slurry until uniform;

Step 8, closing the first grout stop valve 13 and the second grout stop valve 10, opening the grout stop valve of the first grout inlet pipe 23, and turning on the grout pump 22;

Step 9. Circulate the grouting to the design time, turn off the grouting pump 22, remove the sample cylinder and remove its bottom cover 15, and place the sample cylinder without disturbing the internal filling of the sample cylinder, so that the inside of the sample cylinder The excess slurry is free to drain under the action of its own weight;

Step 10. After the residual slurry in the sample cylinder is consolidated and hardened, reassemble the sample cylinder to the simulation device, and use the method described in steps 1-5 to measure and calculate the termination permeability coefficient K _fi ;

Step 11. According to the initial permeability coefficient K _in and the final permeability coefficient K _fi of the sample, calculate the grouting plugging efficiency η as follows:

In the formula: K _in is the initial permeability coefficient of the sample; K _fi is the termination permeability coefficient; η is the plugging efficiency of grouting;

Using the method described in Example 2, the plugging efficiency of the selected quick-setting formula grouting at different times was calculated, and the results are shown in Table 1.

Table 1 Quantitative evaluation of plugging efficiency of quick-setting formula

It can be seen from Table 1 that the selected quick-setting formula is used to grout different samples for different times. As time goes on, the grouting plugging efficiency gradually increases, which reflects the whole process of grouting plugging the loose leakage medium from the data level.

Example 3

Embodiment 3 of the present invention provides a method for quantitative evaluation of grouting simulation in loose leakage formations, which is matched with the device provided in Embodiment 1, and the grouting effects of ordinary cement slurry and the quick-setting formula selected in Embodiment 2 are evaluated respectively , including the following steps:

Step 1. Fill the sample cylinder with pebbles and gravels with a particle size of 20-40mm selected in the test to simulate loose leakage formations;

Step 2. Close the slurry stop valve of the first slurry inlet pipe 23, weigh the selected grouting formula according to the amount, add it to the slurry storage tank, and start the mixer to mix the slurry until uniform;

Step 3. Close the first grout stop valve 13 and the second grout stop valve 10, open the grout stop valve of the first grout inlet pipe 23, and turn on the grout pump 22;

Step 4, using the data acquisition system to record the readings of the first pressure gauge 18 and the second pressure gauge 4 once per minute, and the data is graphed by computer, so as to qualitatively analyze the leakage characteristics of the slurry and the sealing state of the formation;

Step 5. After the test is completed, turn off the power of the device, disconnect the detachable connection, and clean the device by module.

The grouting formula in this embodiment is ordinary cement grout and quick-setting grouting formula, and the grouting simulation is carried out by using the two, and the test results are shown in Fig. 2 .

According to Fig. 2, it can be seen that the device of the present invention and its qualitative evaluation function can compare the applicability of different grouting materials to loose leakage formations. A better plugging effect is specifically reflected in that the pump pressure will continue to increase as the slurry solidifies, which indicates that the quick-setting formula has better resistance to slurry loss caused by its own weight and external pressure. However, even if the ordinary cement slurry is circulated for 60 minutes, due to the slow hydration of the slurry, the rheological properties have not changed, resulting in the loss of the slurry along the seepage channel, which is reflected in the smooth pump pressure and no increase.

The above description does not limit the present invention in any form. Although the present invention has been disclosed by the above-mentioned embodiments, it is not intended to limit the present invention. The technical content disclosed above can be used to make some changes or be modified into equivalent embodiments of equivalent changes, but any simple modifications and equivalent changes made to the above embodiments according to the technical essence of the present invention will not deviate from the content of the technical solution of the present invention and modifications, all still belong to the scope of the technical solution of the present invention.

Claims (10)

1. A loose and lost stratum grouting simulation device is characterized by comprising a circulating grouting system, a plugging efficiency evaluation system and a data acquisition system, wherein the circulating grouting system is composed of a slurry storage tank, a first slurry inlet pipe (23) with a slurry stop valve, a grouting pump (22), a second slurry inlet pipe (21), a buffer tank (20), a third slurry inlet pipe (17) and a slurry outlet pipe (7); the plugging efficiency evaluation system comprises a first flow meter (19), a second flow meter (3), a second pressure gauge (14), a first slurry stop valve (13), a sample cylinder, a third pressure gauge (11) and a second slurry stop valve (10); the data acquisition system comprises a first pressure gauge (18), a first digital camera (8), an image acquisition computer (6), a second digital camera (5) and a fourth pressure gauge (4);

the upper part of the slurry storage tank is communicated with the upper part of the sample cylinder through a slurry outlet pipe (7), and the bottom of the slurry storage tank is communicated with the input end of a grouting pump (22) through a first slurry inlet pipe (23); the output end of the grouting pump (22) is communicated with the lower part of the buffer tank (20) through a second grout inlet pipe (21); the upper part of the buffer tank (20) is communicated with the bottom of the sample cylinder through a third slurry inlet pipe (17);

the second flow velocity meter (3) and the fourth pressure gauge (4) are both arranged on the slurry outlet pipe (7); the third pressure gauge (11), the second slurry stop valve (10), the second pressure gauge (14) and the first slurry stop valve (13) are all arranged on the sample cylinder; the first flow rate meter (19) and the first pressure gauge (18) are both arranged on the third slurry inlet pipe (17);

the image acquisition computer (6) is respectively and electrically connected with the first digital camera (8) and the second digital camera (5); the first digital camera (8) is over against the fourth pressure gauge (4), and the second digital camera (5) is over against the first pressure gauge (18).

2. The loose and lost stratum grouting simulation device as claimed in claim 1, wherein the slurry storage tank comprises a cylinder (26) with a flange, a slurry storage tank steel frame (24), a top cover (2), a motor (1), a stirring shaft and a bottom cover (25) with a slurry outlet circular hole, the first slurry inlet pipe (23) is communicated with the slurry outlet circular hole, the top cover (2) and the bottom cover (25) are respectively connected to the upper end and the lower end of the cylinder (26), the bottom cover (25) is installed on the slurry storage tank steel frame (24), the motor (1) is installed on the top cover (2), the center of the top cover (2) is provided with a circular hole, the upper end of the stirring shaft penetrates through the circular hole and then is connected with a rotating shaft of the motor (1), the right upper side wall of the cylinder (26) with the flange is provided with a through slurry inlet circular hole, and the slurry outlet pipe (7) is communicated with the slurry inlet circular hole.

3. A simulation device for grouting in a unconsolidated lost formation according to claim 2, characterized in that three layers of sealing rings are installed between the cylinder (26) and the bottom cover (25).

4. The loose and lost stratum grouting simulation device as claimed in claim 1, wherein the sample cylinder comprises a sample cylinder (12) with a flange, a sample cylinder top cover (9), a sample cylinder steel frame (16) and a sample cylinder bottom cover (15) with a sample grouting round hole, the sample cylinder top cover (9) and the sample cylinder bottom cover (15) are respectively installed at the upper end and the lower end of the sample cylinder (12), the sample cylinder bottom cover (15) is installed on the sample cylinder steel frame (16), and the third grouting pipe (17) is communicated with the sample grouting round hole; and the left upper side wall of the sample cylinder (12) is provided with a through sample slurry outlet circular hole, and the slurry outlet pipe (7) is communicated with the sample slurry outlet circular hole.

5. The loose leakage formation grouting simulation device according to claim 4, wherein sealing rings are arranged between the sample cylinder (12) and the sample cylinder top cover (9) and the sample cylinder bottom cover (15).

6. The device for simulating grouting of a loose and lost formation, according to claim 4, is characterized in that two through threaded holes are formed in the side wall of the sample cylinder (12), and the first grout stop valve (13) and the second grout stop valve (10) are respectively in threaded connection with the two through threaded holes.

7. The loose and lost stratum grouting simulation device according to claim 6, wherein free ends of the first grout stopping valve (13) and the second grout stopping valve (10) are respectively provided with a second pressure gauge (14) and a third pressure gauge (11) in a threaded connection mode, and the second pressure gauge and the third pressure gauge are used for measuring the water head difference of upper and lower flow sections of a injected medium.

8. The loose and lost stratum grouting simulation device as claimed in claim 1, wherein the first flow rate meter (19) and the first pressure gauge (18) are both installed on the third grout inlet pipe (17) in a threaded connection mode; the second flow velocity meter (3) and the fourth pressure meter (4) are both installed on the slurry outlet pipe (7) in a threaded connection mode.

9. A loose lost stratum grouting simulation method is characterized in that the loose lost stratum grouting simulation device according to any one of claims 1-8 is adopted, and the loose lost stratum grouting simulation method specifically comprises the following steps:

step 1, filling gravel stones selected in a test in a sample cylinder, and simulating a loose and lost stratum;

step 2, closing a pulp stop valve of the first pulp inlet pipe (23), and adding water into the pulp storage tank;

step 3, opening a first grout stop valve (13) and a second grout stop valve (10), simultaneously opening a grout stop valve of a first grout inlet pipe (23), and starting a grouting pump;

step 4, after the water flow rate is stable, reading the flow rate from the first flowmeter (19)QReading the water pressure P from a second pressure gauge (14) ₁ Reading the water pressure P from a third pressure gauge (11) ₂ ；

Step 5, calculating the initial permeability coefficient K of the simulated stratum by adopting the following calculation formula _in ：

In the formula:Lis the vertical center distance between the second pressure gauge and the third pressure gauge, and the unit is cm,Fis the internal section area of the sample cylinder in cm ² ；QFlow rate in cm read for the first odometer ³ /s；P ₁ The unit of the water pressure read by the second pressure gauge is kPa;P ₂ the water pressure read by a third pressure gauge is in kPa;

step 6, recording the initial permeability coefficient, discharging circulating water in the device, and closing a slurry stop valve of the first slurry inlet pipe (23);

step 7, weighing the selected grouting formula according to the amount, adding the grouting formula into a slurry storage tank, and starting a stirrer to mix the slurry uniformly;

step 8, closing the first grout stop valve (13) and the second grout stop valve (10), opening the grout stop valve of the first grout inlet pipe (23), and starting the grouting pump (22);

step 9, circularly grouting until the design time is reached, closing a grouting pump (22), detaching the sample cylinder, removing a sample cylinder bottom cover (15) of the sample cylinder, and allowing redundant slurry in the sample cylinder to freely run off under the action of self weight under the condition that the filling in the sample cylinder is not disturbed;

step 10, after the residual slurry in the sample cylinder is solidified and hardened, reassembling the sample cylinder to the simulation device, and measuring and calculating the final permeability coefficient by adopting the method in the steps 1-5K _fi ；

Step 11, according to the initial permeability coefficient of the sampleK _in And terminating the permeability coefficientK _fi Calculating grouting plugging efficiencyηThe following:

in the formula:K _in the initial permeability coefficient of the sample is taken as the initial permeability coefficient of the sample;K _fi to terminate the permeability coefficient;ηand the plugging efficiency is realized by grouting.

10. A loose lost stratum grouting simulation method is characterized in that the loose lost stratum grouting simulation device according to any one of claims 1-8 is adopted, and the loose lost stratum grouting simulation method specifically comprises the following steps:

step 1, filling gravel stones selected in a test in a sample cylinder, and simulating a loose and lost stratum;

step 2, closing a grout stop valve of the first grout inlet pipe (23), weighing the selected grouting formula according to the amount, adding the grouting formula into a grout storage tank, and starting a stirrer to mix grout until the grout is uniform;

step 3, closing the first grout stop valve (13) and the second grout stop valve (10), opening the grout stop valve of the first grout inlet pipe (23), and starting the grouting pump (22);

step 4, recording readings of a first pressure gauge (18) and a second pressure gauge (4) once per minute by using the data acquisition system, and forming a graph by using a computer according to the data so as to qualitatively analyze the slurry leakage characteristic and the stratum plugging state;

and 5, after the test is finished, closing the power supply of the device, disconnecting the detachable connection, and cleaning the device in modules.

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