Testing device and method for dense fine sand layer grouting material and slurry vein expansion monitoring

Abstract

The invention discloses a dense fine sand layer grouting material and a test device and method for monitoring slurry vein expansion. The grouting material is composed of superfine cement, superfine slag powder, superfine fly ash, water and an optimizing agent. The test device for monitoring slurry vein expansion comprises a grouting device, a sand layer simulation device and a monitoring device, the grouting device comprises a high-speed motor, a piston type water pump, a slurry storage barrel, a high-pressure hose, a high-speed stirrer, a grouting pipe, an advanced small guide pipe, a flow monitor and a grouting pressure measuring instrument; the sand layer simulation device comprises a sample loading bin, a bearing plate, a jack and a pressure measuring instrument, and can truly simulate a field sand soil occurrence environment; the monitoring device comprises a scanner, an X-ray generator, a point cloud collection system and an image display instrument. The device is simple to operate, effectively avoids the problem that the expansion process of the slurry vein in the sand cannot be directly observed due to the concealment of the grouting reinforcement engineering, and has a certain guiding effect on theoretical research and engineering application of the grouting reinforcement engineering.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and in particular relates to a test device and method for monitoring dense fine sand layer grouting material and slurry vein expansion. Background Art

[0002] The fine sand layer has low bonding strength and poor surrounding rock self-stabilization ability. During the construction of the underground subway tunnel, accidents such as arch block falling and face collapse occurred frequently, which seriously affected the construction progress and the safety of construction personnel. The water-rich sand layer can be treated by freezing, grouting and other methods. The freezing method has the advantages of wide adaptability and good flexibility, but it has problems such as long construction period, high construction cost and high risk during construction. The grouting method can achieve the dual effects of hydraulic plugging and improving the bearing capacity of the surrounding rock, and has been widely used in the field of disaster management of water-rich sand layers in underground projects. In the fine sand layer with a relative density of more than 80%, the traditional cement slurry and cement water glass slurry have a small diffusion radius and cannot effectively reinforce the face. In addition, the grouting reinforcement project has a certain degree of concealment, and the expansion process of the slurry in the soil cannot be effectively observed, and the construction environment is complex and changeable; the experimental method can intuitively, comprehensively and truly reflect the diffusion characteristics of the material, and has become an important means of grouting theory research. Therefore, it has become an urgent problem to develop new grouting materials, develop advance small-duct grouting devices for water-rich sand layers, and explore the diffusion characteristics of new materials to provide a scientific basis for grouting reinforcement projects.

[0003] At present, the new grouting materials and grouting test devices for advanced small tubes in dense fine sand layers have the following main defects: 1) The fine sand layer has a dense structure, which makes the diffusion radius of the existing grouting materials small, and it is impossible to effectively reinforce the dense fine sand layer. In addition, the production process of cement materials has the disadvantages of high energy consumption, high pollution and high carbon dioxide emissions, which is contrary to the current green construction concept; 2) The test device and the small tube are small in size, and the wall effect of the device has a great influence on the test results. It is impossible to truly reflect the slurry diffusion characteristics and cannot truly simulate the on-site grouting conditions; 3) After the grouting test, it is usually necessary to dismantle the test device, check the slurry vein distribution inside the sand, measure the slurry vein thickness, and then speculate on the slurry diffusion morphology during the grouting process, and it is impossible to obtain the slurry vein diffusion morphology in real time. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art, to provide a test device and method for grouting materials for dense fine sand layers and slurry vein expansion monitoring, to develop a new type of water-rich sand layer high-efficiency green grouting material, and to truly simulate the on-site grouting conditions by adopting a large-sized sample loading bin and a full-sized advance small guide tube; to use an X-ray detection device arranged outside the sample loading bin to scan the slurry vein morphology of the sand in the sample loading bin and establish a three-dimensional reconstruction model, so as to obtain the slurry vein distribution morphology inside the sand.

[0005] To solve the problems existing in the existing experiments.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: comprising raw materials and an optimizer, wherein the raw materials are composed of ultrafine cement, slag powder and ultrafine fly ash, the optimizer is composed of a water glass solution and a superplasticizer mixed in a mass ratio of 7:3, the modulus of the water glass solution is 3.25, the Baume degree of the water glass solution is 41.5, the superplasticizer is a polycarboxylic acid water reducer, and the particle size of the dense fine sand layer grouting material is mainly concentrated in 1.4 to 14.7 microns.

[0007] The above-mentioned dense fine sand layer grouting material is characterized in that: the dense fine sand layer grouting material also includes water, and the mass ratio of water to raw materials in the dense fine sand layer grouting material is 0.8:1~1:1; the mass ratio of the ultrafine cement, slag powder and ultrafine fly ash is 4:1:5~4:2:4, and the dosage of the optimizer is 4%~6% of the total mass of the raw materials and water.

[0008] The above-mentioned dense fine sand layer grouting material is characterized in that the mass ratio of water to raw materials in the dense fine sand layer grouting material is 1:1, the mass ratio of the ultrafine cement, slag powder and ultrafine fly ash is 4:2:4, and the dosage of the optimizer is 4% of the total mass of the raw materials and water.

[0009] In addition, the present invention also provides a test device for monitoring the expansion of slurry veins using the above-mentioned dense fine sand layer grouting material, which is characterized by comprising a sand layer simulation device, a grouting device for injecting the dense fine sand layer grouting material into the sand layer simulation device, and a monitoring device for real-time monitoring the expansion of slurry veins in the sand layer simulation device.

[0010] The grouting device comprises a high-speed motor, a piston water pump, a slurry storage barrel, a high-pressure hose, a high-speed mixer, a grouting pipe and an advance small guide tube. The high-speed motor is connected to the piston water pump by a belt, and the high-speed motor is used to provide the required energy for the reciprocating motion of the piston of the piston water pump; the slurry storage barrel is used to store the grouting slurry made of the dense fine sand layer grouting material, the upper part of the high-speed mixer is connected to the top cover plate of the slurry storage barrel by bolts, and the middle and lower parts of the high-speed mixer are both located in the slurry storage barrel, and the grouting slurry can be uniformly stirred at high speed; the slurry extraction port at the bottom of the slurry storage barrel is connected to one end of the high-pressure hose, and the other end of the high-pressure hose is connected to the slurry inlet of the piston water pump, and the grouting slurry is pumped into the grouting pipe through the piston water pump; the slurry outlet of the piston water pump is connected to the tail end of the advance small guide tube through the grouting pipe, and the grouting slurry can be directly injected into the soil.

[0011] The above-mentioned dense fine sand layer grouting material is characterized in that the grouting device also includes a flow monitor and a grouting pressure measuring instrument, and the flow monitor and the grouting pressure measuring instrument are both installed at the slurry outlet of the piston pump. The flow monitor is used to monitor the grouting pressure of the grouting slurry in real time during the grouting process, and the grouting pressure measuring instrument is used to monitor the grouting volume changes of the grouting slurry in real time during the grouting process.

[0012] The above-mentioned dense fine sand layer grouting material is characterized in that: a speed regulating valve capable of adjusting the speed of the high-speed motor is installed on the high-speed motor, and a lower hopper for pouring the dense fine sand layer grouting material into the slurry storage barrel is provided on the top of the slurry storage barrel.

[0013] The above-mentioned dense fine sand layer grouting material is characterized in that: the sand layer simulation device includes a sample loading bin, an upper bearing plate, a middle bearing plate, a lower bearing plate, a pressure applying device, a pressure measuring instrument and a pressure display instrument, the upper bearing plate and the lower bearing plate are arranged in parallel with a distance between them, the upper bearing plate and the lower bearing plate are fixed together by multiple threaded screws and multiple bolts, the sample loading bin is arranged on the upper surface of the lower bearing plate, the middle bearing plate is located on the top of the sample loading bin, the pressure applying device is arranged between the upper bearing plate and the middle bearing plate to apply an overlying load to the soil in the sample loading bin; the pressure measuring instrument is located in the soil 10 cm inside the lower surface of the middle bearing plate for real-time measurement of the pressure in the soil, and the pressure measuring instrument is connected to the pressure display instrument through a wire.

[0014] The above-mentioned dense fine sand layer grouting material is characterized in that: the pressure applying device includes a hydraulic jack and a telescopic rod, the telescopic rod is located above the hydraulic jack, the telescopic rod is welded to the bottom center of the upper bearing plate, the bottom of the hydraulic jack is fixed to the top center of the middle bearing plate, the hydraulic jack and the upper end are connected to the telescopic rod; a plurality of oblique triangular rigid ribs are welded to the upper surface of the middle bearing plate.

[0015] The above-mentioned dense fine sand layer grouting material is characterized in that: the monitoring device includes a scanner, an X-ray generator, a high-voltage generator, a point cloud collection system and an image display. The scanner is installed on the track of the outer bin of the sample loading bin and can perform a 360° scan of the slurry vein diffusion morphology in the sample loading bin. The X-ray generator is arranged on the top of the scanner to monitor the slurry vein diffusion morphology inside the sand. The X-ray generator is connected to the high-voltage generator and the high-voltage generator can provide the X-ray generator with a stable DC high voltage of 100kV to 140kV. The point cloud collection system is connected to the scanner through a wire, and the point cloud collection system is connected to the image display through an optical fiber, which can perform three-dimensional reconstruction of the grouting slurry vein morphology inside the sample bin.

[0016] In addition, the present invention also provides a test method for real-time monitoring of slurry vein expansion in a dense fine sand layer using the above device, which is characterized by comprising the following steps:

[0017] Step 1: Preparation of sand sample: The test uses reshaped sand. In order to ensure that the physical and mechanical properties of the reshaped sand are the same as those of the on-site sand, the particle size distribution and content of the reshaped sand are consistent with those of the original sand, and the porosity is controlled by the relative density index; the minimum porosity of the sand is tested by the vibration hammer method; the maximum porosity of the sand is tested by the slow rotation method of the measuring cylinder;

[0018] Step 2: Sample mixing: According to the maximum porosity and minimum porosity of the sand determined in step 1, the fill mass is determined based on the relative density and soil porosity calculation formula, as shown in the following formulas (1) and (2). After mixing, the sample is placed in a sealed bag for 24 hours to ensure that the moisture inside the sand is evenly distributed;

[0019]

[0020] Where: D r is the relative density; e max is the maximum porosity of sand; e min is the minimum porosity of sand; e is the natural porosity of sand;

[0021]

[0022] Where: G s is the specific gravity of sand particles; w is the moisture content of sand, %; γ w is the density of water, kNm -3 ; γ is the density of sand, kN·m -3 ;

[0023] Step 3: Install the test device: Pass the threaded screw through the small holes reserved around the lower load plate, and fix the lower load plate to the threaded screw with bolts. Then place the sample loading chamber on the upper surface of the middle load plate and install the leading small guide tube.

[0024] Step 4: Sand sample filling: Before the test begins, the sample soil is divided into 3 to 5 parts, added layer by layer into the sample loading bin, and compacted layer by layer using a compactor; then the upper load plate is installed, and the middle load plate and the hydraulic jack are moved to the surface of the sample loading bin through the telescopic rod at the bottom of the upper load plate, and the switch of the hydraulic jack is turned on to load the sample to simulate the real occurrence state of the soil;

[0025] Step 5, slurry preparation: pour ultrafine cement, slag powder and ultrafine fly ash into the slurry storage barrel through the lower hopper according to the mass ratio, add water with the same mass as the raw materials, and fully stir the slurry through a high-speed mixer; then, add the optimizer, stir again, and prepare a dense fine sand layer grouting material; at the same time, connect the grouting pipeline to monitor the grouting volume and grouting pressure in real time during the grouting process;

[0026] Step 6: Injection test: After the dense fine sand layer grouting material is fully mixed, turn on the high-speed motor and adjust the speed through the speed regulating valve; at the same time, turn on the piston pump to absorb the dense fine sand layer grouting material slurry, open the slurry outlet valve, and mix the slurry and inject it into the soil sample;

[0027] Step 7, grouting completion: The grouting volume is used as the sign of grouting completion. The single hole grouting volume calculation formula is shown in the following formula (3); 1 hour after the grouting is completed, the test device is dismantled, and the piston pump and grouting pipe are flushed with clean water to prevent the slurry from solidifying and causing damage to the piston pump;

[0028] Q=πR 2 Lnα (3)

[0029] Where: Q is the injection volume of slurry in a single hole, m 3 ; R is the slurry diffusion radius; L is the length of the grouting section; n is the natural porosity of sand; α is the formation filling rate.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. In the present invention, a new type of high-efficiency, green, dense fine sand layer grouting material with a water-solid ratio of 1:1, a mass ratio of slag powder, ultrafine fly ash and ultrafine cement of 4:2:4, and an optimizer dosage of 4% is developed, which solves the problems of small diffusion radius of cement slurry at the current stage, inability to effectively reinforce the tunnel face, high energy consumption, high carbon dioxide emissions, etc.

[0032] 2. In the present invention, the actual sand storage environment is truly simulated by using a sand layer simulation device. Compared with the small-size sample loading chamber used in previous tests, the test device is closer to the actual construction situation and effectively avoids the influence of the device interface effect on the test results. In addition, in the present invention, the on-site grouting process is truly simulated by using a small advance guide tube commonly used in the on-site construction process.

[0033] 3. In the present invention, by using monitoring devices evenly arranged on the outer surface of the sample loading bin, the distribution morphology of the slurry veins inside the sand can be obtained.

[0034] The present invention is further described in detail below through the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is an overall schematic diagram of the pulp vein expansion monitoring test device of the present invention.

[0036] Figure 2 It is a structural schematic diagram of the load-bearing plate in the present invention.

[0037] Figure 3 for Figure 2 Top view of the .

[0038] Figure 4 This is a schematic diagram of the positional relationship between the sample loading chamber, the track, the X-ray generator and the scanner of the present invention.

[0039] Figure 5 This is the slurry diffusion diagram of ordinary cement.

[0040] Figure 6 This is a curve chart of the change of ordinary cement grouting pressure-grouting volume-grouting time.

[0041] Figure 7 It is the slurry vein diffusion diagram of the dense fine sand layer grouting material of the present invention.

[0042] Figure 8 It is a curve diagram of the changes of grouting pressure-grouting amount-grouting time of the dense fine sand layer grouting material of the present invention.

[0043] Description of reference numerals:

[0044] 1—grouting device; 1-1—high-speed electric motor; 1-2—piston pump;

[0045] 1-3—slurry storage barrel; 1-4—high-pressure hose; 1-5—high-speed mixer;

[0046] 1-6—Grouting pipe; 1-7—Advanced small guide tube; 1-8—Flow monitor;

[0047] 1-9—Grouting pressure measuring instrument; 1-10—Regulating valve 1-11—Slurry inlet;

[0048] 1-12—slurry outlet; 2—sand layer simulation device; 2-1—sample loading chamber;

[0049] 2-2—upper bearing plate; 2-3—middle bearing plate; 2-4—lower bearing plate;

[0050] 2-5—pressure measuring instrument; 2-6—pressure display instrument; 2-7—telescopic rod;

[0051] 2-8—bolt; 2-9—hydraulic jack; 2-10—lower hopper;

[0052] 2-11—threaded screw; 2-12—oblique triangular rigid rib plate; 2-13—external chamber of the specimen loading chamber;

[0053] 3—Monitoring device; 3-1—Scanner; 3-2—X-ray generator;

[0054] 3-3—Point cloud collection system; 3-4—Image display device; 3-5—Track;

[0055] 3-6—High voltage generator; 4—Soil. DETAILED DESCRIPTION

[0056] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0057] The dense fine sand layer grouting material of the present invention is described by Examples 1-3:

[0058] Example 1

[0059] The dense fine sand layer grouting material of this embodiment includes raw materials and an optimizer, wherein the raw materials are composed of ultrafine cement, slag powder and ultrafine fly ash, the optimizer is composed of a mixture of water glass solution and a superplasticizer in a mass ratio of 7:3, the modulus of the water glass solution is 3.25, the Baume degree of the water glass solution is 41.5, the superplasticizer is a polycarboxylic acid water reducer, and the particle size of the dense fine sand layer grouting material is mainly concentrated in 1.4 to 14.7 microns.

[0060] The dense fine sand layer grouting material also includes water, and the mass ratio of water to raw materials in the dense fine sand layer grouting material is 1:1; the mass ratio of the ultrafine cement, slag powder and ultrafine fly ash is 4:2:4, and the dosage of the optimizer is 4% of the total mass of the raw materials and water.

[0061] Example 2

[0062] The dense fine sand layer grouting material of this embodiment includes raw materials and an optimizer, wherein the raw materials are composed of ultrafine cement, slag powder and ultrafine fly ash, the optimizer is composed of a mixture of water glass solution and a superplasticizer in a mass ratio of 7:3, the modulus of the water glass solution is 3.25, the Baume degree of the water glass solution is 41.5, the superplasticizer is a polycarboxylic acid water reducer, and the particle size of the dense fine sand layer grouting material is mainly concentrated in 1.4 to 14.7 microns.

[0063] The dense fine sand layer grouting material also includes water, and the mass ratio of water to raw materials in the dense fine sand layer grouting material is 0.8:1; the mass ratio of the ultrafine cement, slag powder and ultrafine fly ash is 4:1:5, and the dosage of the optimizer is 6% of the total mass of the raw materials and water.

[0064] Example 3

[0065] The dense fine sand layer grouting material of this embodiment includes raw materials and an optimizer, wherein the raw materials are composed of ultrafine cement, slag powder and ultrafine fly ash, the optimizer is composed of a mixture of water glass solution and a superplasticizer in a mass ratio of 7:3, the modulus of the water glass solution is 3.25, the Baume degree of the water glass solution is 41.5, the superplasticizer is a polycarboxylic acid water reducer, and the particle size of the dense fine sand layer grouting material is mainly concentrated in 1.4 to 14.7 microns.

[0066] The dense fine sand layer grouting material also includes water, and the mass ratio of water to raw materials in the dense fine sand layer grouting material is 0.9:1; the mass ratio of the ultrafine cement, slag powder and ultrafine fly ash is 4:1.5:4.5, and the dosage of the optimizer is 5% of the total mass of the raw materials and water.

[0067] The dense fine sand layer grouting material prepared by the present invention is compared with ordinary cement slurry. Figure 5 , Figure 6 , Figure 7 and Figure 8 shown.

[0068] From the comparison in the above figure, it can be seen that the diffusion radius of ordinary cement slurry in the dense fine sand layer is about 7 cm, and the diffusion radius is small, which is not injectable in the fine sand layer. The diffusion radius of the slurry vein of the new grouting material reaches about 30 cm, indicating that the new grouting material has better diffusion characteristics. Therefore, the dense fine sand layer grouting material prepared by the present invention solves the problems of the small diffusion radius of cement slurry at this stage, which cannot effectively reinforce the tunnel face and has high energy consumption and high carbon dioxide emissions.

[0069] The experimental device for monitoring the expansion of pulp veins of the present invention is described by Example 4:

[0070] Example 4

[0071] like Figures 1 to 4 As shown, the present invention is a test device for monitoring the expansion of slurry veins using dense fine sand layer grouting materials, including a sand layer simulation device 2, a grouting device 1 for injecting the dense fine sand layer grouting material into the sand layer simulation device 2, and a monitoring device 3 for real-time monitoring the expansion of slurry veins in the sand layer simulation device 2.

[0072] The grouting device 1 comprises a high-speed motor 1-1, a piston water pump 1-2, a slurry storage barrel 1-3, a high-pressure hose 1-4, a high-speed mixer 1-5, a grouting pipe 1-6 and an advance small guide tube 1-7. The high-speed motor 1-1 is connected to the piston water pump 1-2 by a belt. The high-speed motor 1-1 is used to provide the required energy for the reciprocating motion of the piston of the piston water pump 1-2; the slurry storage barrel 1-3 is used to store the grouting slurry made of the dense fine sand layer grouting material. The upper part of the high-speed mixer 1-5 is connected to the top cover plate of the slurry storage barrel 1-3 by bolts. The middle and lower parts of the high-speed mixer 1-5 are located in the slurry storage barrel 1-3, which can stir the grouting slurry at high speed and uniformly to prevent the slurry from sedimentation and agglomeration; the slurry extraction port at the bottom of the slurry storage barrel 1-3 is connected to one end of the high-pressure hose 1-4, and the other end of the high-pressure hose 1-4 is connected to the slurry inlet 1-11 of the piston pump 1-2 and the grouting slurry is pumped into the grouting pipe 1-6 through the piston pump 1-2; the slurry outlet 1-12 of the piston pump 1-2 is connected to the tail end of the advance small guide tube 1-7 through the grouting pipe 1-6, and the grouting slurry can be directly injected into the soil. Among them, the speed of the high-speed motor 1-1 is 0~5000r / min, and the grouting pressure that can be provided is 0~5MPa, and the grouting rate is 0~30L / min, which meets the test requirements; there are 2 piston pumps 1-2, which are connected together by bolts; the volume of the slurry storage barrel 1-3 is 80L. The speed of the high-speed mixer 1-5 when in use is generally 2800r / min, and the slurry can be uniformly stirred at high speed.

[0073] The advanced small conduits 1-7 are commonly used in subway construction. Steel welded pipe, 750mm long, 300mm long pipe head, no holes in the tail 250mm, the remaining part is arranged in a plum blossom shape with an interval of 100mm Overflow hole.

[0074] The grouting device 1 also includes a flow monitor 1-8 and a grouting pressure measuring instrument 1-9, both of which are installed at the grouting outlet of the piston pump 1-2. The flow monitor 1-8 is used to monitor the grouting pressure of the grouting slurry in real time during the grouting process, and the grouting pressure measuring instrument 1-9 is used to monitor the grouting volume change of the grouting slurry during the grouting process.

[0075] The high-speed motor 1-1 is equipped with a speed regulating valve 1-10 capable of regulating the speed of the high-speed motor 1-1, thereby controlling the grouting pressure, and truly simulating the on-site grouting conditions. The top of the grout storage barrel 1-3 is provided with a lower hopper 2-10 for pouring the dense fine sand layer grouting material into the grout storage barrel 1-3.

[0076] The sand layer simulation device 2 includes a sample loading chamber 2-1, an upper bearing plate 2-2, a middle bearing plate 2-3, a lower bearing plate 2-4, a pressure applying device, a pressure measuring instrument 2-5 and a pressure display instrument 2-6. The upper bearing plate 2-2 and the lower bearing plate 2-4 are arranged in parallel with a distance between them. The upper bearing plate 2-2 and the lower bearing plate 2-4 are fixed together by multiple threaded screws 2-11 and multiple bolts 2-8. The sample loading chamber 2-1 is arranged on the upper surface of the lower bearing plate 2-4. The middle load-bearing plate 2-3 is located at the top of the sample loading chamber 2-1, and the pressure applying device is arranged between the upper load-bearing plate 2-2 and the middle load-bearing plate 2-3 to apply an overlying load to the soil 4 in the sample loading chamber 2-1; the pressure measuring instrument 2-5 is located in the soil 4 10 cm inside the lower surface of the middle load-bearing plate 2-3 and is used to measure the pressure in the soil in real time to ensure the accurate application of the overlying load. The pressure measuring instrument 2-5 is connected to the pressure display instrument 2-6 through a wire and can display the overlying load value in real time.

[0077] The sample loading bin 2-1, the upper bearing plate 2-2, the middle bearing plate 2-3 and the lower bearing plate 2-4 are all made of steel. A 25mm small hole is reserved in the center of the lower bearing plate 2-4 and the sample loading bin 2-1 to facilitate the installation of the advance small catheter 1-7; the front end and the tube body of the advance small catheter 1-7 pass through the bottom center of the lower bearing plate 2-4 and the bottom center of the sample loading bin 2-1 from bottom to top and are located in the soil 4. There are 6 small holes distributed around the upper bearing plate 2-2 and the lower bearing plate 2-4 for installing the threaded screw 2-11. The sample loading bin 2-1 has a thickness of 10mm, a height of 800mm and an inner diameter of 600mm. The upper bearing plate 2-2 and the lower bearing plate 2-4 have a thickness of 25mm and a diameter of 800mm, and the threaded screw 2-11 is evenly distributed around the upper bearing plate 2-2 and the lower bearing plate 2-4. The middle load-bearing plate 2-3 is located on the top of the sample loading chamber 2-1, and has a thickness of 20 mm and a diameter of 600 mm.

[0078] The pressure applying device includes a hydraulic jack 2-9 and a telescopic rod 2-7, wherein the telescopic rod 2-7 is located above the hydraulic jack 2-9, and the telescopic rod 2-7 is welded at the bottom center of the upper bearing plate 2-2. The bottom of the hydraulic jack 2-9 is fixed at the top center of the middle bearing plate 2-3. The hydraulic jack 2-9 and the upper end are connected to the telescopic rod 2-7, and the middle bearing plate 2-3 can be directly moved to apply corresponding ground stress to the sand in the sample loading chamber 2-1. A plurality of oblique triangular rigid ribs 2-12 are welded on the upper surface of the middle bearing plate 2-3, so that the overlying load can be evenly transferred to the sand medium, avoiding the occurrence of stress concentration during loading; the telescopic rod 2-7 welded at the bottom of the upper bearing plate 2-2 can directly adjust the middle bearing plate 2-3, saving the time of manual dismantling.

[0079] The hydraulic jack 2-9 is located between the middle load plate 2-3 and the upper load plate 2-2, and can provide an overburden load of 0-1MPa, which can truly simulate the sand storage environment. The pressure measuring instrument 2-5 is buried 10cm below the surface of the middle load plate to measure the soil pressure during loading, with a range of 0-1MPa and a comprehensive error of ±3kPa, which effectively ensures the loading accuracy.

[0080] The monitoring device 3 is arranged on the surface of the outer bin of the sample loading bin, and can obtain the distribution morphology of the slurry veins inside the sand. The monitoring device 3 includes a scanner 3-1, an X-ray generator 3-2, a high-voltage generator 3-6, a point cloud collection system 3-3 and an image display 3-4. The scanner 3-1 is installed on the track 3-5 of the outer bin 2-13 of the sample loading bin, and can perform a 360° scan of the slurry vein diffusion morphology in the sample loading bin 2-1. The X-ray generator 3-2 is arranged on the top of the scanner 3-1 to monitor the slurry vein diffusion morphology inside the sand. The X-ray generator 3-2 is connected to the high-voltage generator 3-6, and the high-voltage generator 3-6 can provide the X-ray generator 3-2 with a stable DC high voltage of 100kV to 140kV, ensuring the smooth and normal operation of the X-ray generator 3-2; the point cloud collection system 3-3 is connected to the scanner 3-1 through a wire, and the point cloud collection system 3-3 is connected to the image display 3-4 through an optical fiber, and the grouting slurry vein morphology in the sample loading bin is reconstructed in three dimensions. A slurry distribution model is established to intuitively display the shape of slurry veins.

[0081] The detection angle of the scanner 3-1 is 20° to 30°, and the diffusion morphology of the pulp veins inside the sample loading chamber can be scanned 360°. The number of scanners 3-1 and X-ray generators 3-2 can be multiple. The point cloud collection system 3-3 is CloudCompare point cloud processing software.

[0082] The test method for real-time monitoring of slurry vein expansion in a dense fine sand layer of the present invention is described by Example 5:

[0083] Example 5

[0084] The test method of this embodiment using a test device to monitor the expansion of slurry veins in a dense fine sand layer in real time includes the following steps:

[0085] Step 1: Preparation of sand sample: The test uses reshaped sand. In order to ensure that the physical and mechanical properties of the reshaped sand are the same as those of the on-site sand, the particle size distribution and content of the reshaped sand are consistent with those of the original sand, and the porosity is controlled by the relative density index; the minimum porosity of the sand is tested by the vibration hammer method; the maximum porosity of the sand is tested by the slow rotation method of the measuring cylinder;

[0086] Step 2: Sample mixing: According to the maximum porosity and minimum porosity of the sand determined in step 1, the fill mass is determined based on the relative density and soil porosity calculation formula, as shown in the following formulas (1) and (2). After mixing, the sample is placed in a sealed bag for 24 hours to ensure that the moisture inside the sand is evenly distributed;

[0087]

[0088] Where: D r is the relative density; e max is the maximum porosity of sand; e min is the minimum porosity of sand; e is the natural porosity of sand;

[0089]

[0090] Where: G s is the specific gravity of sand particles; w is the moisture content of sand, %; γ w is the density of water, kNm -3 ; γ is the density of sand, kN·m -3 ;

[0091] Step 3, test device installation: pass the threaded screw 2-11 through the small holes reserved around the lower bearing plate 2-4, and fix the lower bearing plate 2-4 to the threaded screw 2-11 through the bolts 2-8, then place the sample loading chamber 2-1 on the upper surface of the middle bearing plate 2-3, and install the leading small guide tube 1-7;

[0092] Step 4: Sand sample filling: Before the test begins, the sample soil is divided into 3 to 5 parts, added layer by layer into the sample loading bin 2-1, and compacted layer by layer using a compactor; then the upper bearing plate 2-2 is installed, and the middle bearing plate 2-3 and the hydraulic jack 2-9 are moved to the surface of the sample loading bin 2-1 through the telescopic rod 2-7 at the bottom of the upper bearing plate 2-2, and the switch of the hydraulic jack 2-9 is turned on to load the sample to simulate the real occurrence state of the soil;

[0093] Step 5, slurry preparation: pour ultrafine cement, slag powder and ultrafine fly ash into the slurry storage barrel 1-3 through the lower hopper 2-10 according to the mass ratio, add water with the same mass as the raw materials, and fully stir the slurry through a high-speed mixer; then, add the optimizer, stir again, and prepare a dense fine sand layer grouting material; at the same time, connect the grouting pipeline, and monitor the grouting amount and grouting pressure in real time during the grouting process;

[0094] Step 6, injection test: after the dense fine sand layer grouting material is fully mixed, turn on the high-speed motor 1-1 and adjust the speed through the speed regulating valve 1-10; at the same time, turn on the piston pump 1-2 to absorb the dense fine sand layer grouting material slurry, open the slurry outlet valve, and mix the slurry and inject it into the soil sample;

[0095] Step 7, grouting is completed: the grouting volume is used as the sign of the completion of grouting, and the single hole grouting volume calculation formula is shown in the following formula (3); 1 hour after the grouting is completed, the test device is dismantled, and the piston pump 1-2 and the grouting pipe are rinsed with clean water to prevent the slurry from solidifying and causing damage to the piston pump 1-2;

[0096] Q=πR 2 Lnα (3)

[0097] Where: Q is the injection volume of slurry in a single hole, m 3 ; R is the slurry diffusion radius; L is the length of the grouting section; n is the natural porosity of sand; α is the formation filling rate.

[0098] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A dense fine sand layer grouting material, characterized in that: The invention comprises raw materials and an optimizer, wherein the raw materials are composed of ultrafine cement, slag powder and ultrafine fly ash, the optimizer is composed of a water glass solution and a superplasticizer mixed in a mass ratio of 7:3, the modulus of the water glass solution is 3.25, the Baume degree of the water glass solution is 41.5, the superplasticizer is a polycarboxylic acid water reducer, and the particle size of the dense fine sand layer grouting material is mainly concentrated in 1.4 to 14.7 microns.

2. A dense fine sand layer grouting material according to claim 1, characterized in that: The dense fine sand layer grouting material also includes water, and the mass ratio of water to raw materials in the dense fine sand layer grouting material is 0.8:1 to 1:1; the mass ratio of the ultrafine cement, slag powder and ultrafine fly ash is 4:1:5 to 4:2:4, and the dosage of the optimizer is 4% to 6% of the total mass of the raw materials and water.

3. A dense fine sand layer grouting material according to claim 2, characterized in that: The mass ratio of water to raw materials in the dense fine sand layer grouting material is 1:1, the mass ratio of ultrafine cement, slag powder and ultrafine fly ash is 4:2:4, and the dosage of the optimizer is 4% of the total mass of raw materials and water.

4. A test device for monitoring slurry vein expansion using the dense fine sand layer grouting material as claimed in claim 2, characterized in that: The invention comprises a sand layer simulation device (2), a grouting device (1) for injecting the dense fine sand layer grouting material into the sand layer simulation device (2), and a monitoring device (3) for real-time monitoring of the expansion of the slurry veins in the sand layer simulation device (2). The grouting device (1) comprises a high-speed motor (1-1), a piston pump (1-2), a slurry storage barrel (1-3), a high-pressure hose (1-4), a high-speed mixer (1-5), a grouting pipe (1-6) and an advance small guide tube (1-7). The high-speed motor (1-1) and the piston pump (1-2) are connected together via a belt. The high-speed motor (1-1) is used to provide the energy required for the reciprocating motion of the piston of the piston pump (1-2). The slurry storage barrel (1-3) is used to store the grouting slurry made of the dense fine sand layer grouting material. The upper part of the high-speed mixer (1-5) is connected to the top cover plate of the slurry storage barrel (1-3). The middle and lower parts of the high-speed mixer (1-5) are both located in the slurry storage barrel (1-3) and can stir the grouting slurry at a high speed and uniformly; the slurry extraction port at the bottom of the slurry storage barrel (1-3) is connected to one end of a high-pressure hose (1-4); the other end of the high-pressure hose (1-4) is connected to the slurry inlet (1-11) of the piston-type water pump (1-2), and the grouting slurry is pumped into the grouting pipe (1-6) through the piston-type water pump (1-2); the slurry outlet (1-12) of the piston-type water pump (1-2) is connected to the tail end of the advance small guide tube (1-7) through the grouting pipe (1-6), and the grouting slurry can be directly injected into the soil.

5. A pulp vein expansion monitoring test device according to claim 4, characterized in that: The grouting device (1) also includes a flow monitor (1-8) and a grouting pressure measuring instrument (1-9), wherein the flow monitor (1-8) and the grouting pressure measuring instrument (1-9) are both installed at the grouting outlet of the piston pump (1-2), the flow monitor (1-8) is used to monitor the grouting pressure of the grouting slurry in real time during the grouting process, and the grouting pressure measuring instrument (1-9) is used to monitor the grouting volume change of the grouting slurry in real time during the grouting process.

6. A pulp vein expansion monitoring test device according to claim 3, characterized in that: The high-speed motor (1-1) is provided with a speed regulating valve (1-10) capable of regulating the speed of the high-speed motor (1-1), and the top of the slurry storage barrel (1-3) is provided with a lower hopper (2-10) for pouring the dense fine sand layer grouting material into the slurry storage barrel (1-3).

7. A pulp vein expansion monitoring test device according to claim 3, characterized in that: The sand layer simulation device (2) comprises a sample loading chamber (2-1), an upper bearing plate (2-2), a middle bearing plate (2-3), a lower bearing plate (2-4), a pressure applying device, a pressure measuring instrument (2-5) and a pressure display instrument (2-6); the upper bearing plate (2-2) and the lower bearing plate (2-4) are arranged in parallel with a distance between them; the upper bearing plate (2-2) and the lower bearing plate (2-4) are fixed together by a plurality of threaded screws (2-11) and a plurality of bolts (2-8); the sample loading chamber (2-1) is arranged On the upper surface of the lower bearing plate (2-4), the middle bearing plate (2-3) is located on the top of the sample loading chamber (2-1), and the pressure applying device is arranged between the upper bearing plate (2-2) and the middle bearing plate (2-3) to apply an overlying load to the soil (4) in the sample loading chamber (2-1); the pressure measuring instrument (2-5) is located in the soil (4) 10 cm inside the lower surface of the middle bearing plate (2-3) and is used to measure the pressure in the soil in real time, and the pressure measuring instrument (2-5) is connected to the pressure display instrument (2-6) through a wire.

8. A pulp vein expansion monitoring test device according to claim 7, characterized in that: The pressure applying device comprises a hydraulic jack (2-9) and a telescopic rod (2-7), wherein the telescopic rod (2-7) is located above the hydraulic jack (2-9), the telescopic rod (2-7) is welded to the bottom center of the upper bearing plate (2-2), the bottom of the hydraulic jack (2-9) is fixed to the top center of the middle bearing plate (2-3), and the upper end of the hydraulic jack (2-9) is connected to the telescopic rod (2-7); and a plurality of oblique triangular rigid rib plates (2-12) are welded to the upper surface of the middle bearing plate (2-3).

9. A pulp vein expansion monitoring test device according to claim 4, characterized in that: The monitoring device (3) comprises a scanner (3-1), an X-ray generator (3-2), a high-voltage generator (3-6), a point cloud collection system (3-3) and an image display (3-4). The scanner (3-1) is installed on a track (3-5) of an outer chamber (2-13) of a sample loading chamber and can perform a 360° scan on the slurry vein diffusion morphology in the sample loading chamber (2-1). The X-ray generator (3-2) is arranged on the top of the scanner (3-1) and is used to monitor the slurry vein diffusion morphology inside the sand. The X-ray generator (3-2) is connected to the high-voltage generator (3-6) and the high-voltage generator (3-6) can provide the X-ray generator (3-2) with a stable DC high voltage of 100 kV to 140 kV. The point cloud collection system (3-3) is connected to the scanner (3-1) via a wire, and the point cloud collection system (3-3) is connected to the image display (3-4) via an optical fiber, so as to perform a three-dimensional reconstruction on the grouting slurry vein morphology inside the sample chamber.

10. A test method for real-time monitoring of slurry vein expansion in a dense fine sand layer using the device as claimed in claim 7, characterized in that: The following steps are involved: Step 1: Preparation of sand sample: The test uses reshaped sand. In order to ensure that the physical and mechanical properties of the reshaped sand are the same as those of the on-site sand, the particle size distribution and content of the reshaped sand are consistent with those of the original sand, and the porosity is controlled by the relative density index; the minimum porosity of the sand is tested by the vibration hammer method; the maximum porosity of the sand is tested by the slow rotation method of the measuring cylinder; Step 2: Sample mixing: According to the maximum porosity and minimum porosity of the sand determined in step 1, the fill mass is determined based on the relative density and soil porosity calculation formula, as shown in the following formulas (1) and (2). After mixing, the sample is placed in a sealed bag for 24 hours to ensure that the moisture inside the sand is evenly distributed; Where: D r is the relative density; e max is the maximum porosity of sand; e min is the minimum porosity of sand; e is the natural porosity of sand; Where: G s is the specific gravity of sand particles; w is the moisture content of sand, %; γ w is the density of water, kNm -3 ; γ is the density of sand, kN·m -3 ; Step 3, test device installation: pass the threaded screw (2-11) through the small holes reserved around the lower bearing plate (2-4), and fix the lower bearing plate (2-4) to the threaded screw (2-11) by bolts (2-8), then place the sample loading chamber (2-1) on the upper surface of the middle bearing plate (2-3), and install the leading small guide tube (1-7); Step 4: Sand and soil sample filling: before the test begins, the sample soil is divided into 3 to 5 parts, added layer by layer into the sample loading bin (2-1), and compacted layer by layer using a compactor; then the upper bearing plate (2-2) is installed, and the middle bearing plate (2-3) and the hydraulic jack (2-9) are moved to the surface of the sample loading bin (2-1) through the telescopic rod (2-7) at the bottom of the upper bearing plate (2-2), and the switch of the hydraulic jack (2-9) is turned on to load the sample to simulate the real occurrence state of the soil; Step 5, slurry preparation: pour ultrafine cement, slag powder and ultrafine fly ash into the slurry storage barrel (1-3) through the lower hopper (2-10) according to the mass ratio, add water with the same mass as the raw materials, and fully stir the slurry through a high-speed mixer; then, add the optimization agent, stir again, and prepare a dense fine sand layer grouting material; at the same time, connect the grouting pipeline, and monitor the grouting volume and grouting pressure in real time during the grouting process; Step 6, injection test: after the dense fine sand layer grouting material is fully mixed, turn on the high-speed motor (1-1) and adjust the speed through the speed regulating valve (1-10); at the same time, turn on the piston pump (1-2) to absorb the dense fine sand layer grouting material slurry, open the slurry outlet valve, and mix the slurry and inject it into the soil sample; Step 7, grouting is completed: the grouting volume is used as the sign of the completion of grouting, and the single hole grouting volume calculation formula is shown in the following formula (3); 1 hour after the completion of grouting, the test device is dismantled, and the piston pump (1-2) and the grouting pipe are flushed with clean water to prevent the slurry from solidifying and causing damage to the piston pump (1-2); Q=πR 2 Lna (3) Where: Q is the injection volume of slurry per hole, m 3 ; R is the slurry diffusion radius; L is the length of the grouting section; n is the natural porosity of sand; α is the formation filling rate.

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