Method for preparing and testing special-shaped slurry-rock combination in high-pressure environment

Abstract

The invention provides a preparation and test method of a special-shaped slurry-rock assembly in a high-pressure environment, and belongs to the field of preparation of special-shaped slurry-rock assemblies, and the preparation and test method comprises the following steps: selecting rock mass sections of the same batch, processing the rock mass sections into standard cylinder sizes, and prefabricating various fracture samples through linear cutting equipment; placing the fracture sample in a sample cabin, setting a confining pressure environment, and pumping slurry into the sample cabin according to a set grouting pressure; respectively monitoring the resistance change of the slurry and the pressure change of different heights in the sample cabin and recording the acoustic characteristics of the medium in the sample cabin; after grouting is completed, the mixture is placed in a curing box, and slurry-rock combination bodies in different forms are obtained after curing; a plurality of different types of artificial fracture samples are designed and prepared to simulate common complex fracture structures in actual engineering, so that the complex fractures are accurately and controllably prefabricated; and grouting and consolidation are carried out in a high-pressure environment simulating ground stress, so that the consistency and engineering applicability of the sample are ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of special-shaped slurry-rock combination preparation, and particularly relates to a preparation and test method of special-shaped slurry-rock combination under high-pressure environment. BACKGROUND

[0002] With the increasing scale and depth of underground engineering in China, deep underground engineering has become an important development direction in the fields of mining, water conservancy, transportation and the like. The State's Guiding Opinions on Deeply Promoting the Intelligent Construction of Mines and Promoting the Safe Development of Mines clearly states that innovation-driven should be adhered to, basic research should be strengthened, and the research on key theories such as deep mining rock mechanics and rock stratum control should be focused on.

[0003] However, under the long-term geological evolution and artificial excavation disturbance, the surrounding rock often bears a lateral support pressure higher than its strength peak value, resulting in the development of a large number of weak surface structures such as joints and fractures in the rock mass. These discontinuous surface structures seriously weaken the integrity and stability of the surrounding rock, which is one of the core technical problems faced by underground engineering.

[0004] As an effective means to improve the mechanical properties of fractured rock mass, grouting reinforcement technology has been widely used in coal mines, tunnels, water conservancy and other engineering fields in recent years. By filling the fractures with slurry, not only can the rock mass be repaired and stress concentration be reduced, but also the integrity and strength of the rock mass can be improved, thereby enhancing the stability of the surrounding rock. Although a large number of scholars have carried out systematic research on the performance of grouting materials and grouting methods, the laboratory test system has gradually improved, but the evaluation of the grouting reinforcement effect still faces great challenges in complex engineering practice. Among them, the non-uniformity of the spatial distribution of fractures, the uncertainty of the slurry filling effect, and the mechanism of the slurry-rock coupling are still not clear, and the research on the seepage and mechanical response of the composite rock mass after grouting is still insufficient.

[0005] Previous studies have shown that the mechanical behavior of the "slurry-rock" composite medium after grouting is influenced by factors such as matrix rock, slurry vein structure, and slurry-rock bonding interface, and exhibits complex force-flow coupling characteristics. The geometric characteristics of fractures such as ductility, roughness, and opening have a significant impact on their permeability and experimental response, but current simulation research on the complexity of these fracture characteristics is still limited.

[0006] The preparation quality of a sample is an important basis for ensuring the validity of test data in laboratory research. Currently, most fracture rock mass tests use gypsum, cement and other materials to prepare similar material samples, or artificially cut fractures in rock samples and then perform grouting simulation. Although this type of sample preparation method has the advantages of strong operability and low cost, the mechanical properties of the materials used are quite different from those of natural rock masses, and the grouting process is not simulated under high pressure. However, existing research simplifies the fracture structure morphology in the modeling process, ignores the influence of the opening, inclination, distribution state and combination of the fracture structure on the water sand migration path, especially lacks analysis of the migration behavior under the structure of special-shaped channels (such as turn-back, multi-turn, branch, etc.), and it is difficult to accurately depict the complex disaster channel evolution process in the actual mining area. The sample cannot truly reflect the actual mechanical and seepage behavior of the fractured rock mass.

[0007] In addition, the commonly used "slurry-rock" sample preparation method in the prior art is usually completed in a normal pressure environment. The process generally includes: injecting a cement-based slurry (or other simulated grouting material) into a pre-set fracture or cavity, usually using gravity pouring, manual injection, or low-pressure pump injection, and curing and forming at normal temperature and pressure. The main principle of this type of preparation process is to form a slurry vein structure through physical filling and cementation. The raw materials are generally cement, gypsum, fine sand and other simulation materials, and the ratio is mainly set by experience. The process conditions are unstable.

[0008] However, compared with the high-pressure grouting environment in actual engineering, this normal-pressure grouting and consolidation method cannot simulate the compaction effect, pore structure reconstruction and micro-damage of the fractured rock mass during the grouting process. The "slurry-rock" sample has a simple structure and weak interface, and cannot accurately reflect the actual strengthening effect of the slurry vein on the strength, permeability and other properties of the rock mass after high-pressure grouting. SUMMARY

[0009] In order to overcome some of the problems mentioned in the background, the present application provides a preparation and test method of a special-shaped slurry-rock combination under high pressure, to at least partially solve the above problems.

[0010] According to the technical scheme of the present application, a preparation method of a special-shaped slurry-rock combination under high pressure is provided, which comprises the following steps:

[0011] S1. Selecting a homogeneous rock mass segment from the same batch and processing it into a standard cylindrical size of Φ50mmx100mm, and pre-preparing a plurality of fracture samples through a wire cutting device;

[0012] S2. Placing the fracture sample in a sample chamber, setting a confining pressure environment, and pumping the slurry into the sample chamber according to the set grouting pressure;

[0013] S3. Monitoring the change of the slurry resistance, the pressure change at different heights in the sample chamber, and recording the acoustic characteristics of the medium in the sample chamber, respectively.

[0014] S4. After the completion of grouting, the combined sample is taken out and placed in a curing box under the conditions of temperature 20℃ and humidity 95% for 7 days, and different forms of "slurry-rock" combination are obtained after full consolidation.

[0015] Preferably, the plurality of fracture samples include single fracture samples, half-penetrating fracture samples, penetrating fracture samples, cross fracture samples, branch fracture group samples, broken fracture samples, and dissolution fracture samples.

[0016] The fracture distribution forms in the fracture samples include linear, network, cross, and / or branched spatial configurations, and the fracture opening is uniformly controlled within the range of linear cutting accuracy, and is controlled in millimeter level by precise cutting.

[0017] Preferably, the high-pressure grouting consolidation simulation test device includes a sample cabin, a confining pressure cabin, a high-pressure grouting pump, a high-pressure water injection device, a constant-pressure drainage device, a monitoring assembly, and a control system.

[0018] The sample cabin is arranged in the confining pressure cabin, the high-pressure grouting pump is connected to the sample cabin through a grouting pipe penetrating the confining pressure cabin, the high-pressure water injection device is connected to the confining pressure cabin through a water injection pipe, the constant-pressure drainage device is arranged on the side of the sample cabin, the monitoring assembly is arranged on the sample cabin and the confining pressure cabin respectively, and the control system is coupled with the confining pressure cabin, the high-pressure grouting pump, the high-pressure water injection device, the constant-pressure drainage device, and the monitoring assembly to control the work of each component.

[0019] Preferably, it further includes a grouting cabin, the grouting cabin wraps the sample cabin, the top of the grouting cabin is connected to the top surface in the confining pressure cabin through a main body support, the bottom of the grouting cabin and the bottom of the sample cabin are respectively connected to a bottom support, and the bottom support is connected to the bottom surface of the confining pressure cabin through a liftable hydraulic rod.

[0020] The constant-pressure drainage device is connected to the side wall of the grouting cabin, and the constant-pressure drainage device includes fine pore filter cloth, metal support net, and coarse pore filter cloth distributed from close to the sample cabin to far away from the sample cabin.

[0021] Preferably, the monitoring system includes test electrodes, acoustic emission sensors, and micro pressure sensors.

[0022] The number of the test electrodes is two, which are arranged on the bottom surface of the sample chamber, the number of the acoustic emission sensors is two, which are arranged on the outer side wall of the bottom surface and the top surface of the sample chamber respectively, the number of the micro pressure sensors is six, four of which are evenly arranged on the same height side wall of the confining pressure chamber, and the other two are arranged on the top surface of the sample chamber, and the micro pressure sensor adopts Gensors micro pressure sensor PM200-WB, which is small in size, high in precision and resistant to high pressure.

[0023] Preferably, the sample chamber is a cylinder with an inner diameter of 60 mm and a height of 260 mm, and the confining pressure chamber is a cylinder with an inner diameter of 800 mm, a height of 1500 mm, a wall thickness of 20 mm and a maximum bearing pressure of 5 MPa.

[0024] Preferably, the maximum output pressure of the high-pressure grouting pump is 10 MPa, the grouting pressure is 2-8 MPa, and 2-4 MPa is used as a low pressure section: suitable for semi-penetrating, dissolved fissures and other small or weakly connected fissures, reducing the impact of slurry on the rock mass and reducing the risk of secondary damage to the fissures.

[0025] 5-8MPa as a high pressure section: suitable for through-going, broken fissures and other complex spatial structures, the slurry is pushed to branch fissures by higher pressure to improve the bonding strength of the "slurry-rock" interface;

[0026] The grouting material of the high-pressure grouting pump is P.O42.5 ordinary portland cement single slurry of Haibo brand, and the water-cement mass ratio is 1:1~1:1.5, wherein the mass ratio of 1:1-1:1.25 is suitable for broken fissures and other fissures with strong connectivity and long expansion path, which can improve the diffusion range of the slurry; the mass ratio of 1:1.3-1:1.5 has higher slurry viscosity and faster solidification speed, which is suitable for small fissure opening.

[0027] On the other hand, the application also provides a test method of a special-shaped slurry-rock combination under high pressure, characterized in that the different shapes of "slurry-rock" combination are fixed by HPETTS high-pressure environment geotechnical triaxial test system, the permeation pressure difference is 0.5~11MPa (gradient rising), and the confining pressure is always greater than the permeation pressure difference during the unloading / pressurizing process to maintain the stability of the test, the initial confining pressure is set to 16MPa and the corresponding unloading / pressurizing grading gradient, and only the confining pressure is changed during the test.

[0028] The experiment of the different shapes of "slurry-rock" combination under different confining pressures and permeation pressure differences is a conventional high-pressure triaxial permeation test, and the experiment of the different shapes of "slurry-rock" combination under different confining pressures and permeation pressure differences is a multi-stage confining pressure loading and unloading seepage coupling test under triaxial conditions.

[0029] Further, the conventional high-pressure triaxial permeability test of the different morphological "slurry-rock" combinations under different confining pressures and osmotic pressure differences includes the following steps:

[0030] The different morphological combinations are respectively set with 4MPa, 8MPa, 12MPa and 16MPa confining pressures, water inlet pressure and water outlet pressure, the osmotic pressure difference is controlled in the range of 0.5MPa to 11MPa, and the permeability coefficient change is recorded.

[0031] Further, the multi-stage confining pressure loading and unloading seepage coupling test of the different morphological "slurry-rock" combinations under triaxial conditions includes the following steps:

[0032] The different morphological combinations are respectively set with an initial confining pressure of 16MPa and an osmotic pressure difference of 7MPa, and the confining pressure loading and unloading cycle is performed in a grading gradient of 16→14→12→10→8MPa, the seepage time of each stage is 15min, and the law of the periodic change of the permeability coefficient with the confining pressure is monitored.

[0033] Compared with the prior art, the beneficial effects of the present application are that:

[0034] The present application designs and prepares a plurality of different types of artificial fracture samples, the designed fracture types fully consider key control factors such as the geometric morphology, spatial distribution, opening, inclination angle and combination mode of the fractures in the rock mass, so as to simulate the complex fracture structure commonly seen in actual engineering, and then to achieve the precise and controllable prefabrication of the complex fracture; the grouting and consolidation are carried out in a high-pressure environment simulating the ground stress, so as to ensure the consistency of the samples and the repeatability and engineering applicability of the test results. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a special-shaped fracture sample of the embodiment of the present application;

[0036] Figure 2 It is a structural diagram of the high-pressure grouting and consolidation simulation test device of the embodiment of the present application;

[0037] Figure 3 It is a schematic diagram of the internal structure and the connection relationship of each part of the high-pressure grouting and consolidation simulation test device of the embodiment of the present application;

[0038] Figure 4 It is a structural diagram of the constant-pressure drainage device of the embodiment of the present application;

[0039] Figure 5 It is a distribution diagram of the monitoring assembly on the sample cabin of the embodiment of the present application;

[0040] Figure 6 It is a device diagram of the HPETTS high-pressure environment geotechnical triaxial test system of the embodiment of the present application;

[0041] Figure 7 Fig. 2 is a schematic diagram of the change of the permeability coefficient with different confining pressures under the osmotic pressure difference of 7 MPa according to an embodiment of the present application;

[0042] Figure 8 Fig. 2 is a schematic diagram of the change of the permeability coefficient with different confining pressures under the osmotic pressure difference of 7 MPa according to an embodiment of the present application;

[0043] Figure 9 Fig. 3 is a schematic diagram of the overall change of the multi-stage confining pressure and the permeability coefficient according to an embodiment of the present application.

[0044] Fig. 1 is a schematic diagram of the high-pressure water injection device according to an embodiment of the present application, wherein 1 is a high-pressure water injection device, 2 is a sample cabin, 3 is a confining pressure cabin, 4 is a high-pressure grouting pump, and 5 is a control system.

[0045] 21 is a bottom support, 22 is a main body support, 23 is a grouting cabin, 24 is a liftable hydraulic rod, 61 is a fine pore filter cloth, 62 is a metal support net, 63 is a coarse pore filter cloth, 71 is a test electrode, 72 is an acoustic emission sensor, and 73 is a micro pressure sensor. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope.

[0047] The embodiment of the present application provides a preparation method of a special-shaped slurry-rock assembly under a high-pressure environment, including the following steps:

[0048] S1. Selecting a same batch of deep homogeneous rock segments to process into standard cylinder sizes of Φ50 mm*100 mm, and pre-preparing a plurality of fracture samples through a wire cutting device;

[0049] S2. Placing the fracture sample in a sample cabin 2, setting a confining pressure environment, and pumping slurry into the sample cabin 2 according to a set grouting pressure;

[0050] S3. Monitoring the change of the slurry resistance, the pressure change at different heights in the sample cabin, and recording the medium acoustic characteristics in the sample cabin;

[0051] S4. After the grouting is completed, taking out the assembly sample to place in a curing box, curing for 7 days under the conditions of a temperature of 20℃ and a humidity of 95%, and obtaining different forms of “slurry-rock” assemblies after full consolidation.

[0052] In a further embodiment of the present embodiment, the plurality of fracture samples include a single fracture sample, a half-penetrating fracture sample, a penetrating fracture sample, a cross fracture sample, a branch-type fracture group sample, a broken fracture sample, and a dissolution fracture sample;

[0053] The crack distribution pattern in the crack sample includes different spatial configurations such as linear, network, cross and / or branch, the crack opening is uniformly controlled within the range of linear cutting precision, and is controlled in millimeter level through precise cutting.

[0054] In further embodiments of the present embodiment, a high-pressure grouting consolidation simulation test device is included, which comprises a sample cabin 2, a confining pressure cabin 3, a high-pressure grouting pump 4, a high-pressure water injection device 1, a constant-pressure drainage device, a monitoring assembly and a control system 5;

[0055] The sample cabin 2 is arranged in the confining pressure cabin 3, the high-pressure grouting pump 4 is connected to the sample cabin 2 through a grouting pipe penetrating the confining pressure cabin 3, the high-pressure water injection device 1 is connected to the confining pressure cabin 3 through a water injection pipe, the constant-pressure drainage device is arranged on the side of the sample cabin 2, the monitoring assembly is arranged on the sample cabin 2 and the confining pressure cabin 3 respectively, and the control system 5 is coupled with the confining pressure cabin 3, the high-pressure grouting pump 4, the high-pressure water injection device 1, the constant-pressure drainage device and the monitoring assembly to control the work of each component.

[0056] In further embodiments of the present embodiment, a grouting cabin 23 is also included, which wraps the sample cabin 2, the top of the grouting cabin 2 is connected to the top surface in the confining pressure cabin 3 through a main body support 22, the bottom of the grouting cabin 23 and the bottom of the sample cabin 2 are respectively connected to the bottom support 21, and the bottom support 21 is connected to the bottom surface of the confining pressure cabin 3 through a liftable hydraulic rod 24;

[0057] The constant-pressure drainage device is connected to the side wall of the grouting cabin 23, and the constant-pressure drainage device includes fine pore filter cloth 61, metal support net 62 and coarse pore filter cloth 63 distributed from close to the sample cabin 2 to far away from the sample cabin 2.

[0058] In further embodiments of the present embodiment, the monitoring system includes test electrodes 71, acoustic emission sensors 72 and micro pressure sensors 73.

[0059] The number of test electrodes 71 is two, which are arranged on the bottom surface of the sample cabin 2, the number of acoustic emission sensors 72 is two, which are arranged on the outside wall of the bottom surface and the top surface of the sample cabin 2 respectively, and the number of micro pressure sensors 73 is six, four of which are evenly arranged on the same height side wall of the confining pressure cabin 3, and the other two are arranged on the top surface of the sample cabin 2.

[0060] In further embodiments of the present embodiment, the sample cabin 2 is a cylinder with an inner diameter of 60 mm and a height of 260 mm, and the confining pressure cabin 3 is a cylinder with an inner diameter of 800 mm, a height of 1500 mm, a wall thickness of 20 mm and a maximum pressure of 5 MPa.

[0061] In a further implementation form of the present embodiment, the maximum output pressure of the high-pressure grouting pump 4 is 10 MPa, and the grouting pressure is 2-8 MPa.

[0062] The grouting material of the high-pressure grouting pump 4 is a single slurry of P.O 42.5 ordinary portland cement, and the water-cement mass ratio is 1:1-1:1.5. When the mass ratio is 1:1-1:1.25, the slurry is suitable for cracks with strong connectivity and long extension path, and the diffusion range of the slurry can be improved. When the mass ratio is 1:1.3-1:1.5, the viscosity of the slurry is relatively high, and the solidification speed is fast, which is suitable for the scene with small crack opening.

[0063] On the other hand, the present application also provides a test method of a special-shaped slurry-rock assembly under high pressure, characterized in that the different shapes of the "slurry-rock" assembly are fixed by the HPETTS high-pressure environment geotechnical triaxial test system, the penetration pressure difference is 7 MPa, the confining pressure is always greater than the penetration pressure difference during the unloading / pressurizing process to maintain the stability of the test, the initial confining pressure is set to 16 MPa and the corresponding unloading / loading grading gradient is set, and only the confining pressure is changed during the test.

[0064] The test method includes the following steps:

[0065] In a further implementation form of the present embodiment, the regular high-pressure triaxial permeability test of the different shapes of the "slurry-rock" assembly under different confining pressures and penetration pressure differences includes the following steps:

[0066] For different shapes of the assembly, the confining pressures of 4 MPa, 8 MPa, 12 MPa and 16 MPa, the water inlet pressure and the water outlet pressure are set, the penetration pressure difference is controlled in the range of 0.5 MPa-11 MPa, and the change of the permeability coefficient is recorded.

[0067] In a further implementation form of the present embodiment, the multi-level confining pressure loading and unloading seepage coupling test of the different shapes of the "slurry-rock" assembly under triaxial conditions includes the following steps:

[0068] For different shapes of the assembly, the initial confining pressure is set to 16 MPa, the penetration pressure difference is set to 7 MPa, the confining pressure is loaded and unloaded according to the grading gradient of 16→14→12→10→8 MPa, the seepage time of each level is 15 min, and the law of the periodic change of the permeability coefficient with the confining pressure is monitored.

[0069] It should be noted that the present application designs seven representative special-shaped crack types, which are respectively: single crack, semi-penetrating crack, penetrating crack, cross crack, branch crack group, broken crack and dissolution crack.Figure 1 As shown.

[0070] The selected fracture width was uniformly set according to the cutting precision standard of the wire cutting equipment to ensure the consistency of fracture size and the repeatability of the preparation process. To eliminate the influence of parent rock differences on the test results, all samples were selected from the same batch of deep homogeneous rock mass sections to ensure good consistency in mineral composition, structural characteristics, and physical and mechanical properties. The samples were processed into standard cylindrical dimensions of Φ50mm × 100mm.

[0071] The following factors were considered in the design of the fracture:

[0072] Fracture distribution morphology: including different spatial configurations such as linear, network, intersecting, and branching, to simulate common joint groups and fracture structures in rock masses;

[0073] Crack opening (width): uniformly controlled within the precision range of online cutting, and precisely controlled at the millimeter level through tight jointing to ensure that the crack has a relatively consistent grouting resistance under different structures;

[0074] Crack inclination angle: By setting different cutting angles (such as vertical, inclined, curved, etc.), the influence of crack spatial orientation on slurry diffusion path and mechanical reinforcement effect is studied;

[0075] Combined state: By using different structural configurations such as "single fracture", "multiple fracture combination", and "interconnected", we will explore the interaction mechanism between fractures and the synergistic effect of fracture network on grouting performance.

[0076] The systematic changes in the above parameters make the irregularly shaped fracture specimen constructed by this invention superior to the traditional fracture model in terms of structural morphology and engineering representativeness, providing a good research foundation.

[0077] The prefabrication process for irregularly shaped fracture specimens includes:

[0078] Sample selection and basic processing: Select homogeneous deep rock masses from the same batch and process them into standard cylindrical samples of Φ50 mm × 100 mm to ensure the consistency of mineral composition, structure and mechanical properties, and eliminate the interference of parent rock differences on the test.

[0079] Irregular fracture design and cutting: Based on simulation requirements, seven fracture types were designed (single fracture, semi-continuous fracture, continuous fracture, intersecting fracture, dendritic fracture group, fractured fracture, and dissolution fracture), and fractures were prefabricated using wire cutting equipment.

[0080] Uniformly control the crack width (based on wire cutting precision, at the millimeter level) to ensure that the grouting resistance of cracks in different structures is basically consistent;

[0081] Cutting fissures according to design angle (vertical, inclined, curved, etc.), simulating the influence of different inclination angles on slurry migration;

[0082] Through the "single / multi-fissure combination" "crossing intercommunication" and other configurations, the synergistic effect of the fissure network is simulated.

[0083] High-pressure grouting sample preparation system composition and preparation process: after the preparation of the fissured rock sample, the high-pressure grouting consolidation simulation test device is used for grouting treatment. Figure 2 and Figure 3 As shown in the device consists of six main parts:

[0084] 1. Sample cabin: inner diameter 60 mm, height 260 mm, internal laying of filter geotextile, preventing slurry leakage, allowing only water to be discharged.

[0085] 2. Confining pressure cabin: used to provide a simulated ground stress environment, inner diameter 800 mm, height 1500 mm, wall thickness 20 mm, maximum pressure 5 MPa; the inner wall of the confining pressure cabin 3 is provided with an array of micro sensors x4, which are evenly distributed at an angle of 90°, can accurately capture the pressure field distribution in the confining pressure cabin, and provide confining pressure environment data support for the test.

[0086] 3. High-pressure water injection device: composed of confining pressure pump, providing stable confining pressure for the confining pressure cabin 3.

[0087] 4. Constant pressure drainage device: under high pressure conditions, during the slurry dehydration and consolidation process in the sample cabin 2, the water in the slurry enters the confining pressure cabin 3 through the side wall of the sample cabin 2 and the filter geotextile, and is adjusted and discharged through the constant pressure drainage device, maintaining a stable confining pressure environment; the drainage side wall adopts a three-layer composite structure, the inner layer of fine pore filter cloth 61 (pore size 0.1 mm) fine filters slurry impurities, the middle layer of metal support net 62 (thickness 1 mm) ensures the stability of the filter cloth shape, and the outer layer of coarse pore filter cloth 63 (pore size 1 mm) takes into account the preliminary filtration and protection, improving the reliability of drainage and backwashing, and adapting to complex experimental medium working conditions.

[0088] 5. Monitoring system: (1) resistivity test electrode and direct current stable power supply, test electrode 71 is located at the bottom of sample chamber 2, connected with direct current stable power supply by wire, including direct current power supply and electrode, monitoring the change of slurry resistance, frequency is 5 min / time, input voltage AC 220V±10%, output DC 0~60V, 3A; (2) acoustic emission sensor 72 and miniature pressure sensor 73 are also arranged on the inner wall of sample chamber 2, which are respectively used for monitoring the acoustic characteristics of medium and the pressure change at different heights in the bin (see Figure 3 To ensure that the sensor works stably during the grouting process and is not affected by slurry erosion and pressure impact, the device is designed from three aspects of structural protection, material adaptation and installation process:

[0089] Structural protection: sealing isolation components are arranged at the contact parts of various sensors and grouting. For example, the sensor installation interface adopts the structure of "external thread + double silicon rubber sealing ring", which fills the gap and blocks the slurry leakage path during grouting by the elastic deformation of the sealing ring; the acoustic sensor 72 and the miniature pressure sensor 73 are additionally provided with a metal protective sleeve (thickness 2mm, with acoustic / pressure conducting holes, which can ensure signal acquisition and block direct slurry washing);

[0090] Material adaptation: the key contact components of the sensor are made of slurry corrosion resistant materials. For example, the metal parts in contact with the cement slurry adopt 316L stainless steel, which can resist the corrosion of cement hydration products (such as calcium hydroxide, etc.); the sealing parts are made of fluorine rubber, which can maintain good elasticity and sealing property in strong alkaline environment of cement slurry, avoiding sensor failure caused by material degradation;

[0091] Installation process: the sensor mounting hole adopts the "stepped hole + pouring sealant plugging" process. During installation, the sensor is first accurately embedded in the stepped hole, and then high-strength, water-resistant pouring sealant is used to fill the gap, which can fix the position of the sensor and further isolate the slurry, forming a "mechanical seal + chemical seal" double protection, so as to ensure that the sensor can stably collect data in the high pressure and strong corrosion environment of grouting.

[0092] 6. Computer control system.

[0093] During grouting, the slurry is injected into the sample chamber 2 by the high-pressure grouting pump 4 and the stable pressure is maintained. Under high pressure, the slurry quickly fills the fissure and gradually dehydrates and consolidates. The curing conditions are temperature 20℃, humidity 95%, curing time 7 days, and then used for high-pressure triaxial permeability test and mechanical property test.

[0094] To enhance the engineering applicability and representativeness of the test results, the grouting pressure and water-cement ratio are strictly selected according to the parameters used in the actual construction process to ensure that the diffusion path, diffusion range and filling effect of the slurry in the test fractured rock mass are as close as possible to the actual behavior in the grouting process. The slurry is pumped into the sample chamber 2 by the high-pressure grouting pump 4, and a high-pressure environment is maintained. The slurry gradually consolidates under high pressure to form a slurry consolidated body. By selecting the same grouting parameters as the actual project, the underground grouting environment and slurry distribution characteristics are maximized, thereby reducing the possible deviation between the test conditions and the actual working conditions.

[0095] (d) The main body of the high-pressure water injection device 1 is a confining pressure pump. The confining pressure pump pumps water into the confining pressure chamber 3 and maintains stable confining pressure conditions.

[0096] (e) The constant-pressure drainage device is used to adjust the pressure relief and maintain a stable confining pressure environment during the process of slurry consolidation by water loss in the sample chamber 2 under high pressure.

[0097] (f) The electrode monitoring system mainly consists of resistivity test electrodes and a direct current stable power supply. The test electrodes 71 are located at the bottom of the sample chamber 2 and are connected to the direct current stable power supply by wires. During the grouting process, the resistance change of the slurry in the sample chamber 2 is monitored by the electrodes to reflect the consolidation state of the slurry. The resistivity monitoring frequency in this test is 5 minutes per time. The direct current stable power supply provides the initial voltage for resistivity testing. The input voltage is AC 220V±10%, the frequency is 50Hz, and the output is DC 0~60V 3A.

[0098] The operation of high-pressure grouting to prepare "slurry-rock" combination is as follows:

[0099] Equipment inspection and preparation; check the connection of each component of the high-pressure grouting consolidation simulation test device (sample chamber 2, confining pressure chamber 3, high-pressure grouting pump 4, sensors, computer control system, etc.) to ensure normal operation, especially the connectivity of the four arrayed micro sensors 73 distributed at an angle of 90°, the acoustic emission sensor 72, the micro pressure sensor 73 and the resistivity test electrode.

[0100] Confirm that the three-layer composite structure (inner layer fine pore filter cloth 0.1mm, middle layer metal support net 1mm, outer layer coarse pore filter cloth 1mm) of the upper drainage side wall of the sample chamber 2 is intact to prevent slurry leakage.

[0101] Sample installation; lower the height-adjustable hydraulic rod 24 of the sample chamber 2 to place the pre-prepared irregular fracture sample into the sample chamber 2; lift the height-adjustable hydraulic rod 24 to fix the sample and ensure that the sample position is stable and aligned with the grouting port, sensors and other components.

[0102] Surrounding pressure environment setting; water is injected into the surrounding pressure cabin 3 through the high-pressure water injection device 1 (surrounding pressure pump), and the surrounding pressure is gradually increased to the test set value (reference to the actual engineering ground stress, the maximum pressure bearing of the device is 5MPa); the pressure field distribution in the surrounding pressure cabin 3 (through the array sensor) and the working state of each sensor are checked again to ensure that the surrounding pressure is stable.

[0103] The high-pressure grouting operation is:

[0104] Slurry preparation: P.O 42.5 ordinary portland cement single slurry is used, and the water-cement ratio is 1:1;

[0105] Grouting parameters: start the high-pressure grouting pump 4, set the grouting pressure to 3MPa (which can be adjusted according to the demand, the maximum output pressure is 10MPa), and pump the slurry into the sample cabin 2;

[0106] Process monitoring:

[0107] Resistivity monitoring: through the bottom electrode of the sample cabin 2, the slurry resistance change is recorded once every 5min (direct current stable power supply: input AC220V±10%, output DC0~60V / 3A), which reflects the slurry consolidation state;

[0108] Acoustic and pressure monitoring: the acoustic characteristics of the medium are recorded through the acoustic emission sensor 72, and the pressure change at different heights in the bin is monitored through the micro pressure sensor 73;

[0109] Drainage control: during the water loss and consolidation process of the slurry, the water enters the surrounding pressure cabin 3 through the filter cloth, and the constant-pressure drainage device is adjusted to release the pressure and keep the surrounding pressure stable.

[0110] Curing treatment: after grouting is completed, the "slurry-rock" combined body sample is taken out and placed in a curing box, and cured under the condition of temperature 20℃ and humidity 95% for 7 days, and after full consolidation, it is used for subsequent tests.

[0111] Experimental part and part of experimental results:

[0112] The HPETTS high-pressure environment geotechnical triaxial test system is adopted, including three types of different crack depth test pieces in the "slurry-rock" combined body, the fixed permeation pressure difference is 7MPa (according to the ground stress and water permeation pressure data in the report), at the same time, in order to ensure that the surrounding pressure is always greater than the permeation pressure difference during the unloading / loading process, thereby maintaining the stability of the test, the initial surrounding pressure is set to 16MPa and the corresponding unloading / loading grading gradient is set, and only the surrounding pressure is changed during the test.

[0113] The test of the present application mainly designs two test schemes, scheme one is the conventional high-pressure triaxial permeation test of different forms of "slurry-rock" combined body under different surrounding pressures and permeation pressure differences; scheme two is the multi-stage surrounding pressure loading and unloading seepage coupling test of different forms of "slurry-rock" combined body under triaxial conditions.

[0114] Scheme one (conventional high pressure triaxial permeability test):

[0115] For different combinations of forms, set different confining pressure (4MPa, 8MPa, 12MPa, 16MPa, etc.), water pressure and water pressure, control the osmotic pressure difference (0.5MPa~11MPa), record the change of permeability coefficient;

[0116] Operation points: ensure that the confining pressure is always greater than the osmotic pressure difference (such as osmotic pressure difference 7MPa, initial confining pressure set to 16MPa), ensure the stability of the test.

[0117] Scheme two (multi-stage confining pressure loading and unloading seepage coupling test):

[0118] Set the initial confining pressure 16MPa, the osmotic pressure difference 7MPa, and the confining pressure loading and unloading cycle according to the grading (16→14→12→10→8MPa), each level seepage time 15min, monitor the law of permeability coefficient with periodic changes in confining pressure.

[0119] The specific parameters of the triaxial permeability experiment of scheme one are shown in Table 1, wherein the type of the test piece Z-X-Y represents the depth of the fracture in the test piece, 25mm; X represents the confining pressure of the test piece, MPa; Y represents the osmotic pressure difference of the test piece, MPa.

[0120] Table 1

[0121]

[0122] The experimental results of this scheme are shown in Table 2.

[0123] Table 2

[0124]

[0125]

[0126] The parameters of the multi-stage confining pressure loading and unloading seepage coupling test of scheme two are shown in Table 3.

[0127] Table 3

[0128] Test No. Initial confining pressure (MPa) Difference in osmotic pressure (MPa) Unloading / loading step confining pressure (MPa) Per-step seepage time (min) 1 16 7 16、14、12、10、8 15

[0129] The permeability coefficient changes with different confining pressures under each osmotic pressure difference, the permeability coefficient changes with different confining pressures under osmotic pressure difference 7MPa, and the overall changes of multi-stage confining pressure and permeability coefficient are shown in Figure 5 、 Figure 6 and Figure 7 .

[0130] It is known that under low osmotic pressure difference (3Mpa) conditions, lower confining pressure level (4-8MPa) has a certain degree of inhibitory effect on the seepage of the sample. With the increase of water pressure, the inhibitory effect of medium confining pressure level (8-12MPa) is weakened. When the confining pressure increases to a high level (12-16MPa), the inhibitory effect of confining pressure is the strongest, and the osmotic pressure difference is very weak.

[0131] Under medium osmotic pressure difference (5Mpa) conditions, the permeability coefficient continues to increase, and the increase of osmotic pressure difference and water pressure makes the permeability of the sample increase.

[0132] Under high osmotic pressure difference (7Mpa) conditions, the increase of water pressure makes the permeability coefficient increase, which is similar to the change trend under medium osmotic pressure difference conditions. If the water pressure remains constant, the permeability coefficient decreases with the increase of the difference between water pressure and confining pressure (water pressure is less than confining pressure). When the water pressure is much smaller than the confining pressure, it is difficult for water to seep into the sample, and the seepage capacity of the combination is very weak.

[0133] The permeability coefficient presents obvious periodic variation characteristics, which is synchronized with the periodic increase and decrease of confining pressure. Specifically, in the first cycle, the permeability coefficient maintains a high level and the fluctuation amplitude is significant; in the second and third cycles, the overall level of permeability coefficient gradually decreases, and the fluctuation amplitude further decreases; at the end of the third cycle, the permeability coefficient continues to decrease and reaches a low level, the overall change trend is consistent with the change of seepage volume, which proves the effectiveness of the test data.

[0134] (1) In the initial stage, under the initial confining pressure conditions, the permeability of the rock mass is relatively strong, and the fluctuation with the change of confining pressure is significant, which indicates that the permeability coefficient is sensitive to the change of confining pressure in this stage.

[0135] (2) In the subsequent stage, with the gradual increase of confining pressure, the rock mass density increases, and the permeation path is compressed, resulting in a significant decrease in permeability coefficient. At the end of the stage, the permeability coefficient has decreased to a low level, indicating that the permeability of the rock mass under high confining pressure conditions is significantly weakened, which may be due to the compaction effect that further limits the flowability of the permeation channel.

[0136] (3) Under the same confining pressure conditions, the permeability coefficients of different cycles show obvious differences. With the increase of cycle period, the permeability coefficient under the same loading and unloading stage is smaller than that of the previous period, indicating that the "cement-rock" combination may experience stress accumulation and structural change after repeated loading and unloading, and the influence of confining pressure change on permeability coefficient is more significant. Especially in the final stage of the whole cycle, the permeability coefficient decreases suddenly and reaches the minimum value, indicating that the permeability of the "cement-rock" combination is severely inhibited under high confining pressure conditions.

[0137] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for preparing an irregularly shaped magma-rock composite under high pressure, characterized in that, Includes the following steps: S1. Select the same batch of deep homogeneous rock mass sections and process them into standard cylindrical dimensions of Φ50mm×100mm. Pre-fabricate various fracture samples using wire cutting equipment. S2. Place the cracked sample in the sample chamber, set the confining pressure environment, and pump the grout into the sample chamber according to the set grouting pressure. S3. Monitor the changes in slurry resistance, the pressure changes at different heights in the sample chamber, and record the acoustic properties of the medium in the sample chamber. S4. After grouting is completed, the composite sample is taken out and placed in a curing box. It is cured for 7 days at a temperature of 20℃ and a humidity of 95% to obtain "grout-rock" composites of different shapes after full consolidation.

2. The method for preparing irregularly shaped magma-rock composites under high pressure according to claim 1, characterized in that, The various types of fracture specimens include single fracture specimens, semi-through fracture specimens, through fracture specimens, cross fracture specimens, dendritic fracture group specimens, fractured fracture specimens, and dissolution fracture specimens. The crack distribution morphology in the cracked specimen includes different spatial configurations such as linear, mesh, intersecting and / or branching. The crack opening is uniformly controlled within the range of online cutting accuracy and is controlled at the millimeter level through precise suturing.

3. The method for preparing irregularly shaped magma-rock composites under high pressure according to claim 1, characterized in that, The system includes a high-pressure grouting consolidation simulation test device, which comprises a sample chamber, a confining pressure chamber, a high-pressure grouting pump, a high-pressure water injection device, a constant pressure drainage device, monitoring components, and a control system. The sample chamber is located inside the confining pressure chamber. The high-pressure grouting pump is connected to the sample chamber through a grouting pipe that passes through the confining pressure chamber. The high-pressure water injection device is connected to the confining pressure chamber through a water injection pipe. The constant-pressure drainage device is located on the side of the sample chamber. The monitoring components are respectively located on the sample chamber and the confining pressure chamber. The control system is coupled to the confining pressure chamber, the high-pressure grouting pump, the high-pressure water injection device, the constant-pressure drainage device, and the monitoring components to control the operation of each component.

4. The method for preparing irregularly shaped magma-rock composites under high pressure according to claim 3, characterized in that, It also includes a grouting chamber that encloses the sample chamber. The top of the grouting chamber is connected to the top surface inside the confining chamber via a main support. The bottom of the grouting chamber and the bottom of the sample chamber are respectively connected to a bottom support. The bottom support is connected to the bottom surface of the confining chamber via a liftable hydraulic rod. The constant pressure drainage device is connected to the side wall of the grouting chamber. The constant pressure drainage device includes fine-pore filter cloth, metal support mesh and coarse-pore filter cloth distributed from near the sample chamber to far away from the sample chamber.

5. The method for preparing irregularly shaped magma-rock composites under high pressure according to claim 3, characterized in that, The monitoring system includes test electrodes, an acoustic emission sensor, and a miniature pressure sensor; The number of test electrodes is two, both set on the bottom surface of the sample chamber. The number of acoustic sensors is two, respectively set on the bottom and top outer walls of the sample chamber. The number of micro pressure sensors is six, with four micro pressure sensors evenly set on the side walls at the same height in the confining pressure chamber, and the other two micro pressure sensors respectively set on the top surface of the sample chamber.

6. The method for preparing irregularly shaped magma-rock composites under high pressure according to claim 1, characterized in that, The sample chamber is a cylinder with an inner diameter of 60 mm and a height of 260 mm, and the confining pressure chamber is a cylinder with an inner diameter of 800 mm, a height of 1500 mm, a wall thickness of 20 mm, and a maximum pressure of 5 MPa.

7. The method for preparing irregularly shaped magma-rock composites under high pressure according to claim 3, characterized in that, The maximum output pressure of the high-pressure grouting pump is 10MPa, and the grouting pressure is 2-8MPa; The grouting material injected by the high-pressure grouting pump is Conch brand P.O42.5 ordinary silicate cement single-liquid grout, with a water-cement mass ratio of 1:1-1:1.

5.

8. A test method for irregularly shaped magma-rock assemblages under high pressure according to any one of claims 1-7, characterized in that, The different morphologies of the "magma-rock" assemblies were tested using the HPETTS high-pressure environment triaxial test system. The osmotic pressure difference was fixed at 0.5~11MPa, while ensuring that the confining pressure was always greater than the osmotic pressure difference during the unloading / pressurization process to maintain the stability of the test. An initial confining pressure of 16MPa and corresponding unloading / pressurization graded gradients were set, and only the confining pressure was changed during the test. The experiment included conventional high-pressure triaxial permeability tests on different morphologies of "magma-rock" assemblies under different confining pressures and osmotic pressure differentials, as well as multi-stage confining pressure loading and unloading seepage coupling tests on different morphologies of "magma-rock" assemblies under triaxial conditions.

9. The test method for irregular magma-rock assemblages under high pressure according to claim 8, characterized in that, The conventional high-pressure triaxial permeability tests of the different morphologies of "magma-rock" assemblies under different confining pressures and osmotic pressure differentials include the following steps: For different morphological combinations, confining pressures of 4MPa, 8MPa, 12MPa, and 16MPa, inlet and outlet pressures were set, and the osmotic pressure difference was controlled within the range of 0.5MPa to 11MPa. The changes in permeability coefficient were recorded.

10. The test method for irregularly shaped magma-rock assemblages under high pressure according to claim 8, characterized in that, The multi-stage confining pressure loading and unloading seepage coupling test of different morphologies of "magma-rock" assemblies under triaxial conditions includes the following steps: An initial confining pressure of 16 MPa and a permeability difference of 7 MPa were set for different morphological combinations. The confining pressure was loaded and unloaded in stages according to the gradient of 16→14→12→10→8 MPa, with a seepage time of 15 min for each stage. The periodic change of the permeability coefficient with the confining pressure was monitored.

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