Method for tensile-shear fracture test of high core wall dam mixed clay with gravel without friction influence

Abstract

The application discloses a high core wall dam mixed clay tensile-shear fracture test method without friction influence, which comprises the following steps: S1, collecting soil samples and determining the optimal water content and the maximum dry density; S2, designing various test conditions; S3, combining a front half of a mold and a rear half of the mold; S4, assembling a compaction fracture mold; S5, preparing and compacting the mixed clay soil sample; S6, transferring the compaction fracture mold to a hollow test tank; S7, removing a Z-shaped compaction plate and a rectangular ring wall; S8, suspending the test part of the compaction fracture mold; and S9, carrying out the tensile fracture test or the shear fracture test of the mixed clay of the core wall. In the application, the tensile fracture and the shear fracture characteristics of the mixed clay can be studied on the same test device, and the friction does not need to be considered. The application fundamentally solves the problem that the existing soil body fracture test method cannot be used for determining the fracture characteristics of the mixed clay of the high core wall dam, and fills the blank of the test method of the mixed clay of the high core wall dam.

Description

Technical Field

[0001] This invention relates to the field of geotechnical testing, and designs a test method for the fracture characteristics of gravelly clay mixed with high core wall dams, particularly a tensile-shear fracture test method for gravelly clay mixed with high core wall dams without friction effects. Background Technology

[0002] In the planning and construction of high dams, earth-rock dams are gaining increasing popularity due to their excellent foundation adaptability and economical building materials. my country has the largest number of earth-core rockfill dams, with most concentrated in southwestern China. Statistics show that my country has several earth-core rockfill dams in operation with a height exceeding 100.0m, including Shiziping (136.0m), Xiaolangdi (160.0m), Pubugou (186.0m), Nuozhadu (261.5m), and Lianghekou (295.0m). Dams under construction or planned with a height of 300m include Rumei (315.0m), Gushui (305.0m), Rimian (346.0m), and Qizong (356.0m).

[0003] Traditional low and medium-sized earth-rock dams often use compacted pure clay cores as seepage control systems. However, with increasing construction height, the poor compressive strength of clay becomes increasingly apparent. Uneven settlement between the core and the rockfill mass can cause cracks in the clay core. High-core dams often incorporate gravel into the core to improve its compressive strength and reduce uneven settlement. Core cracks are essentially shear failure, tensile failure, or a combination of shear and tensile failure that occurs when the stress and strain borne by the soil exceed its tensile or shear strength. Currently, there are few studies on the fracture characteristics of gravel-mixed clay cores. Therefore, researching the fracture characteristics of gravel-mixed clay and elucidating the evolution of cracks in gravel-mixed clay has significant engineering and practical value.

[0004] Currently, most soil fracture testing devices are focused on studying the fracture characteristics of clay or sand, and there is a lack of testing devices suitable for studying the fracture characteristics of gravelly clay in high-core wall dams. Since existing soil fracture testing methods cannot be used to determine the fracture characteristics of gravelly clay in high-core wall dams, it is necessary to develop a tensile-shear fracture testing method specifically for gravelly clay in the core of high-core wall dams in Southwest China, to fill this gap in testing methods for this type of soil. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the existing testing techniques and to provide a tensile-shear fracture test method for gravelly clay in high-core wall dams without the influence of friction. This method can measure both the tensile fracture characteristics and the shear fracture characteristics of gravelly clay, thus filling the gap in the test method for fracture characteristics of gravelly clay in high-core wall dams.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for tensile-shear fracture testing of gravelly clay in high-core wall dams without friction effects includes the following steps:

[0008] S1. Collect soil samples and determine their optimum moisture content and maximum dry density under different gravel content;

[0009] S2. Design experiments under various working conditions to study the effects of moisture content, dry density, and gravel content on fracture characteristics, including:

[0010] A) Take soil samples with the same dry density and gravel content and divide them into multiple portions. Adjust each portion of soil sample to different moisture content levels to study the effect of moisture content on fracture characteristics.

[0011] B) Take soil samples with the same moisture content and gravel content and divide them into multiple portions. Adjust each portion of soil sample to different dry density levels to study the effect of dry density on fracture characteristics.

[0012] C) Take soil samples with the same dry density and moisture content and divide them into multiple portions. Adjust each portion of soil sample to different gravel content levels to study the effect of gravel content on fracture characteristics.

[0013] S3, Combining the front half and rear half of the mold:

[0014] Using the same steps, bolts are screwed into the combination block on the first seam plate and the second seam plate and the fixed base plate in sequence to fix the first seam plate and the second seam plate relative to each other on the carrier box, so that the two sets of first seam plates, second seam plates and carrier box together form the front half and rear half of the mold with the same structure.

[0015] S4. Assemble and compact the fracture mold:

[0016] The front and rear halves of the mold are placed symmetrically at the center. The three sets of protrusions are fixedly connected to the corresponding first threaded holes with bolts and installed on the front and rear floating cavities respectively. The front and rear floating cavities are fixedly connected with the cavity connecting plate to form the compaction fracture mold test part. A rectangular ring wall is fitted on its outside to assemble the compaction fracture mold.

[0017] S5. Prepare and compact gravelly clay soil samples:

[0018] The gravelly clay sample prepared in S2 was added into the compaction fracture mold assembled in S4, and compacted using a Z-shaped compaction plate to obtain the gravelly clay sample.

[0019] S6. Transfer the compaction fracture mold to the hollow test chamber. During the transfer, the compacted gravelly clay sample 2, together with the compaction fracture mold 1, is placed into the hollow test chamber 7 using a hoisting rope. Since the hollow test chamber 7 is not filled with water, the compaction fracture mold 1 is in contact with the bottom of the hollow test chamber 7.

[0020] S7. Remove the Z-shaped compaction plate and the rectangular ring wall, while keeping the cavity connecting plate connected to the front and rear halves of the mold.

[0021] S8. Suspend the compaction fracture mold test section until its bottom separates from the bottom wall of the hollow test tank and is in a frictionless state. The process is as follows:

[0022] S8.1. Hydrogen gas is filled into the two sets of airbags at the bottom of the front and rear floating cavities to lift the front and rear floating cavities.

[0023] S8.2 Open the water inlet hole and close the water outlet hole, fill the hollow test tank with water, so that the compaction fracture mold test part floats continuously as the water level rises under the action of buoyancy;

[0024] S8.3. By changing the hydrogen content in the airbags at different locations on the two sets of airbags, the compaction fracture mold test section is leveled.

[0025] S9. The test apparatus is assembled and the tests are carried out, including tensile fracture test S9.1 and shear fracture test S9.2.

[0026] S9.1 Conduct tensile fracture tests on gravelly clay core walls:

[0027] For the fixed compaction fracture mold test section, the cavity connecting plate was removed. The front puller and the rear puller pulled the front half and the rear half of the mold to the sides respectively. The stress and displacement sensor measurement data at the connection end were recorded. The test was stopped when the gravelly clay sample underwent tensile fracture. The stress-strain curve of the gravelly clay sample under tensile fracture was obtained by processing. The tensile fracture characteristics of the gravelly clay sample of the high core wall dam were analyzed.

[0028] S9.2 Conduct shear fracture tests on gravelly clay core:

[0029] In the fixed compaction fracture mold test section, the cavity connecting plate, the first seam plate and the second seam plate were removed. The left and right pushers were respectively pushed the front half and the rear half of the mold towards the center of the test device. The stress and displacement sensor measurement data at the connection end were recorded. The test was stopped when the gravelly clay soil sample underwent shear fracture. The stress-strain curve of the gravelly clay soil sample under shear fracture was obtained by processing. The shear fracture characteristics of the gravelly clay soil sample of the high core wall dam were analyzed.

[0030] Preferably, in S1, the soil sample is gravelly clay from the material yard near the site of the high core wall dam. A heavy compaction instrument is used to conduct a compaction test on the gravelly clay to obtain the optimal moisture content and maximum dry density of the gravelly clay sample with a gravel content of 30% to 50%.

[0031] Preferably, in S2, when designing the test conditions (A), the proposed range for the soil sample moisture content is set to 8.72%–10.34% while keeping other variables constant.

[0032] B) When designing the test conditions, with other variables kept constant, the proposed range for the dry density of the soil sample was set at 2.03 g / cm³. 3 ~16g / cm 3 ;

[0033] C) When designing the test conditions, while keeping other variables constant, the proposed range for the amount of gravel in the soil sample is set to 30%–50%.

[0034] Preferably, the specific operating steps for processing the gravelly clay soil sample in S5 are as follows:

[0035] S5.1 Calculate the required mass of water H, clay C, gravel G, and total mass Y of gravel-mixed clay using the mold volume V, i.e., Y = H + C + G.

[0036] S5.2 Add water of mass H to clay of mass C, place it in a sealed box and let it stand for 24 hours. Add gravel of mass G and stir quickly. Place it in a sealed box again and let it stand for 24 hours.

[0037] S5.3. Add the gravelly clay prepared in S5.2 to the compaction fracture mold test section in N portions. After each addition of gravelly clay, immediately compact the gravelly clay using a Z-shaped compaction plate.

[0038] Preferably, the hydrogen filling amount of the two airbag groups in S8.1 is obtained by calculation, as follows:

[0039] S8.1.1 Collect the mass A of the compaction fracture mold test part and the mass Y of the gravel-mixed clay soil sample, and obtain the total mass of the test body composed of the compaction fracture mold test part and the gravel-mixed clay soil sample as A+Y;

[0040] S8.1.1 By substituting A+Y into the following expression, the buoyancy F(buoyancy) corresponding to A+Y can be obtained;

[0041] A + Y = F(buoyancy) = G(displacement) = ρ(water)gV(displacement)

[0042] Where ρ(water) represents the density of the liquid filled into the hollow test tank, and g is the acceleration due to gravity, taken as 9.8 m / s². 2V (displacement) represents the volume of liquid displaced by the test subject, and G (displacement) represents the volume of water displaced when the test subject floats on the water surface against gravity.

[0043] We can deduce that:

[0044] V(displacement) = (A + Y) / ρ(water)g

[0045] S8.1.2 By substituting the volume V (displaced) of the liquid displaced when the test body floats into the following formula, the minimum mass M of hydrogen gas required for the test body to overcome gravity and float is calculated.

[0046] M = ρ(gas)V(discharge)

[0047] Where ρ(gas) represents the density of hydrogen gas, with a value of 0.089 g / m³. 3 .

[0048] Preferably, the leveling method described in S8.3 is based on the structure of the airbag assembly, which includes multiple airbags arranged in a rectangular array for filling with hydrogen.

[0049] A diaphragm is provided between multiple airbags, and a channel is provided on the diaphragm. A solenoid valve is embedded in the channel. Each airbag is provided with an independent inflation and deflation port, so that multiple airbags can be inflated and deflated simultaneously or the amount of gas in the airbags in a local area can be adjusted.

[0050] The solenoid valve is electrically connected to a remote control chip, and the amount of hydrogen filled into the gasbag is increased or decreased by inputting the specific gasbag number through the remote control.

[0051] Preferably, the inflation of the two airbag groups is as follows:

[0052] When the vertical position of the test subject on the water surface is finely adjusted, multiple solenoid valves open, allowing multiple airbags to communicate with each other, increasing the hydrogen mass P in any one airbag, and the hydrogen in the other airbags is replenished accordingly, thus adjusting the overall height of the test subject on the water surface.

[0053] When the solenoid valve between one of the airbags and the adjacent airbag fails to open due to signal control or malfunction, causing it to be concave relative to the outside, the solenoid valve on this airbag is opened, and the hydrogen mass in each of the other airbags is reduced by P / (n-1) accordingly, where n is the number of airbags in each airbag group.

[0054] When the test body is tilted and needs to be leveled, the solenoid valve is closed, and the hydrogen mass P of a certain airbag in the lower side area of ​​the compaction fracture mold 1 is increased. The increased hydrogen mass P is filled into the corresponding airbag from the external gas supply pipe.

[0055] Preferably, in S9.1, the tensile fracture test procedure for the gravelly clay sample is as follows:

[0056] S9.1.1, Fixed Compaction Fracture Mold Test Section:

[0057] By controlling the front control unit and the rear control unit respectively, the output ends of the front connecting part and the rear connecting part are extended and gradually brought closer to the axial connecting hole in front and the lateral connecting hole in rear. The hydrogen content filled inside the two sets of airbags is finely adjusted so that the axial connecting hole and the lateral connecting hole are at the same height as the front connecting part and the rear connecting part respectively. The front connecting part and the rear connecting part are extended again until they are fixedly connected to the compaction fracture mold test part.

[0058] S9.1.2, Remove the cavity connecting plate and conduct tests:

[0059] Remove the cavity connecting plates that connect the front and rear floating cavities and are located on the left and right sides, and open the front and rear control units. Pull the front and rear connecting parts at a certain rate; record the stress and displacement sensor data connected to the front and rear connecting parts.

[0060] S9.1.3, until the gravelly clay sample reaches tensile fracture and the data is processed:

[0061] The stress and displacement were recorded until the gravelly clay sample fractured under tensile stress. The stress and displacement data were then processed to obtain the stress F (tensile) and displacement L (tensile) experienced by the gravelly clay sample during the tensile fracture test, expressed as follows:

[0062] F(pull) = (|F5| + |F6|) / 2

[0063] L(pull) = (|L5| + |L6|) / 2

[0064] Wherein, F5 and F6 represent the stress data recorded at the front and rear connecting parts, respectively; L5 and L6 represent the displacement data recorded at the front and rear connecting parts, respectively.

[0065] Based on the values ​​of F (tensile) and L (tensile), the stress-strain curves of the gravelly clay soil samples during tensile fracture were obtained. The characteristic parameters of the gravelly clay soil in the high-core wall dam during tensile fracture were analyzed through the tensile fracture stress-strain curves. The characteristic parameters include fracture toughness and fracture energy. Thus, the tensile fracture characteristics of the gravelly clay soil samples in the high-core wall dam were fully understood.

[0066] Preferably, in S9.2, the shear fracture test procedure for the gravelly clay sample is as follows:

[0067] S9.2.1, Fixed Compaction Fracture Mold Test Section:

[0068] By controlling the left and right control sections respectively, the output ends of the left and right connecting parts are extended and gradually brought closer to the axial connecting hole on the left and the lateral connecting hole on the right. The hydrogen content inside the two sets of airbags is finely adjusted so that the axial connecting hole and the lateral connecting hole are at the same height as the left and right connecting parts respectively. The left and right connecting parts are then extended again until they are fixedly connected to the compaction fracture mold test part.

[0069] S9.2.2 Remove the cavity connecting plate to expose the prefabricated joint and conduct a test:

[0070] Remove the cavity connecting plates that connect the front and rear floating cavities and are located on their left and right sides. With the assembly block disconnected from the carrier box, simultaneously use hook pliers to hook into the hooking holes on the positioning blocks on both sides and remove the first seam plate and the second seam plate respectively. Open the left and right control units and advance the left and right connecting parts at a certain rate. Record the data measured by the stress and displacement sensors inside the left and right connecting parts.

[0071] S9.2.3, until the gravelly clay sample undergoes shear fracture and the data is processed:

[0072] The stress and displacement were recorded until the gravelly clay sample underwent shear fracture. The stress and displacement data were then processed to obtain the stress F (shear) and displacement L (shear) experienced by the gravelly clay sample during the shear fracture test, expressed as follows:

[0073] F(shear) = (F3|+|F4) / 2

[0074] L(shear) = (L3|+|L4) / 2

[0075] Wherein, F3 and F4 represent the stress data recorded at the left and right connecting parts, respectively; L3 and L4 represent the displacement data recorded at the left and right connecting parts, respectively.

[0076] Based on the F (shear) and L (shear) values, the stress-strain curves of the gravelly clay soil samples during shear fracture were obtained. The characteristic parameters of the gravelly clay soil in the high-core wall dam during shear fracture were analyzed through the stress-strain curves of shear fracture. The characteristic parameters include fracture toughness and fracture energy. Thus, the shear fracture characteristics of the gravelly clay soil samples in the high-core wall dam were fully understood.

[0077] Preferably, the pulling rates of the front and rear connecting parts are set to multiple levels to study the influence of different loading rates on the tensile fracture characteristics of gravelly clay samples.

[0078] The advancement rates of the left and right connecting parts were set to multiple levels to study the effects of different loading rates on the shear fracture characteristics of gravelly clay samples.

[0079] The present invention has the following beneficial effects:

[0080] (1) The friction-free tensile-shear fracture test method for gravelly clay in high core wall dams provided by the present invention can study the tensile fracture and shear fracture characteristics of gravelly clay on the same test device, fundamentally solving the problem that the existing soil fracture test method cannot be used to determine the fracture characteristics of gravelly clay in high core wall dams, thus filling the gap in the test method for gravelly clay in high core wall dams.

[0081] (2) The frictionless high core wall dam gravel-mixed clay tensile-shear fracture test method provided by the present invention uses the principle of buoyancy to separate the compaction fracture mold test part from the working platform, float it on the water surface, and fix it through the connecting part, which fundamentally solves the friction between the mold and the platform and greatly enriches the test means of gravel-mixed clay fracture characteristics.

[0082] (3) The frictionless high core wall dam gravel-mixed clay tensile-shear fracture test method provided by the present invention can apply tension and propulsion force to the compaction fracture mold test part while fixing the test part of the compaction fracture mold by the pushers on both sides and the pullers at the front and rear. At the same time, the loading rate of the force can be controlled, which provides convenience for studying the influence of different loading rates on the tensile fracture and shear fracture of gravel-mixed clay. Attached Figure Description

[0083] Figure 1 This is a schematic diagram of the overall structure of the tensile-shear fracture testing device provided by the present invention (omitting the cavity connecting plate, rectangular ring wall and Z-shaped compaction plate).

[0084] Figure 2 This is a schematic diagram of the overall structure of the compaction fracture mold in this invention.

[0085] Figure 3 This is a schematic diagram of the structure of the test support part (omitted cavity connecting plate) in this invention.

[0086] Figure 4 In this invention Figure 3 Exploded view of the structure shown.

[0087] Figure 5 This is a diagram illustrating the distribution structure of the airbag assembly in this invention and the changes during the inflation process.

[0088] Figure 6 This is a schematic diagram of the structure of the gravelly clay sample used in this invention.

[0089] Figure 7This is a schematic diagram of the connection structure of the left propeller, right propeller, front puller, rear puller and hollow test tank in this invention.

[0090] Figure 8 This is a schematic diagram of the test process of the frictionless high-core wall dam gravel-mixed clay tensile-shear fracture test device in this invention.

[0091] In the picture:

[0092] 1. Compacting fracture mold;

[0093] 1-1. Front half of the mold; 1-2. Rear half of the mold;

[0094] 1-1-1, First seam plate; 1-1-2, Second seam plate; 1-1-3, Positioning block; 1-1-4, Assembly block; 1-1-5, Lateral push plate; 1-1-6, Axial pull plate; 1-1-7, Fixed base plate; 1-1-8, Axial connection hole; 1-1-9, First threaded hole; 1-2-0, Lateral connection hole;

[0095] 1-3, Anterior Floating Chamber; 1-4, Rear Floating Chamber;

[0096] 1-3-1, Second threaded hole; 1-3-2, Horizontal bubble; 1-3-3, Protrusion; 1-3-4, Airbag assembly;

[0097] 1-5. Cavity connecting plate; 1-6. Rectangular annular wall;

[0098] 1-7, Z-shaped compaction plate; 1-7-1, gap between the compaction plates; 1-7-2, handle at the end of the compaction plate;

[0099] 2. Gravelly-mixed clay soil sample; 2-1. Fractured section of soil sample; 2-2. Front end of soil sample; 2-3. Rear end of soil sample;

[0100] 3. Left thruster; 3-1. Left connecting part; 3-2. Left control part;

[0101] 4. Right-side thruster; 4-1. Right-side connecting part; 4-2. Right-side control part;

[0102] 5. Front traction device; 5-1. Front connecting part; 5-2. Front control part;

[0103] 6. Rear traction device; 6-1. Rear connecting part; 6-2. Rear control part;

[0104] 7. Hollow test tank; 7-1. Water inlet hole; 7-2. Water outlet hole. Detailed Implementation

[0105] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0106] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0107] like Figure 1-7 As shown, the frictionless high-core wall dam gravelly clay tensile-shear fracture test device includes a compaction fracture mold 1 and a hollow test chamber 7. The compaction fracture mold 1 is used to prepare the gravelly clay sample 2. It includes a test bearing part, a rectangular ring wall 1-6, and a Z-shaped compaction plate 1-7. The compaction fracture mold 1 is a centrally symmetrical mold with a rectangular cross-section, which can be used to compact the gravelly clay sample 2 and to conduct tensile and shear fracture tests on the gravelly clay sample 2. The test bearing part, i.e., the test part of the compaction fracture mold, is the part after the compaction fracture mold 1 is prepared by disassembling the rectangular ring wall 1-6 and the Z-shaped compaction plate 1-7. A rectangular groove is opened at the center of the top of the hollow test chamber 7. The hollow test chamber 7 is made of stainless steel, and the inner wall of the groove is coated with a waterproof coating. The groove is filled with water that allows the test bearing part containing the gravelly clay sample 2 to float.

[0108] The prepared gravelly clay sample 2 has a fractured section 2-1, with the front end 2-2 and the rear end 2-3 of the sample on its two sides, respectively. The gravelly clay sample 2 prepared in this invention has a centrally symmetrical structure, which is consistent with the cross-sectional shape of the Z-shaped compaction plate 1-7, and its dimensions are adapted to the inner cavity of the test bearing section. The fractured section 2-1 represents the location where cracks occur during actual tensile or shear fracture.

[0109] The test support unit includes a front half of the mold 1-1, a rear half of the mold 1-2, a front floating cavity 1-3, a rear floating cavity 1-4, and a cavity connecting plate 1-5. The front half of the mold 1-1 and the rear half of the mold 1-2 are detachably mounted on the front floating cavity 1-3 and the rear floating cavity 1-4, respectively. The front floating cavity 1-3 and the rear floating cavity 1-4 are detachably connected by the cavity connecting plate 1-5. The front half of the mold 1-1 and the rear half of the mold 1-2 are the front and rear halves of the mold, respectively, and are set at the front and rear ends of the gravelly clay soil sample 2. They can respectively achieve axial pulling and lateral pushing of the front end 2-2 and the rear end 2-3. During the preparation of gravelly clay sample 2 and its transfer to the hollow test tank 7, the front floating cavity 1-3 and the rear floating cavity 1-4 are connected by the cavity connecting plate 1-5 to form a horizontal and solid integral plate structure. Before the test, the cavity connecting plate 1-5 is removed, allowing the front floating cavity 1-3 and the rear floating cavity 1-4 to move relative to the front half 1-1 and the rear half 1-2 of the mold. In the working state, they are fixedly connected to the front half 1-1 and the rear half 1-2 of the mold, respectively, so that the front half 1-1 and the rear half 1-2 of the mold float stably on the water.

[0110] The test bearing section, together with the rectangular ring wall 1-6 and the Z-shaped compaction plate 1-7, compacts the gravel-mixed clay material of the high core wall dam core wall to form gravel-mixed clay soil sample 2. After the sample is prepared, the rectangular ring wall 1-6 and the Z-shaped compaction plate 1-7 are removed. At this time, the gravel-mixed clay soil sample 2 is loaded in the test bearing section.

[0111] The test bearing is made of aluminum alloy, which has the advantages of high strength and low density, and can minimize the impact of its own weight on the test. During the tensile or shearing process of gravelly clay sample 2, it is convenient to measure the fracture characteristics of gravelly clay.

[0112] The combined structure of the front half 1-1 of the mold and the front floating cavity 1-3 is the same as the combined structure of the rear half 1-2 of the mold and the rear floating cavity 1-4, and the two combined structures are centrally symmetrically distributed. The bottom openings of the front floating cavity 1-3 and the rear floating cavity 1-4 are fitted with airbag assemblies 1-3-4, used to adjust the buoyancy of the front floating cavity 1-3 and the rear floating cavity 1-4 and their floating angle on the water surface. Horizontal air bubbles 1-3-2 are also provided on the front half 1-1 and the front floating cavity 1-3 for inspection. The levelness of the test bearing section loaded with gravelly clay soil sample 2 is measured. In this embodiment, the number of horizontal air bubbles 1-3-2 is set to four, which are respectively set at the four corners of the combined structure of the front floating cavity 1-3 and the rear floating cavity 1-4. Before the test, the state of the horizontal air bubbles 1-3-2 is observed to determine whether the test bearing section loaded with gravelly clay soil sample 2 is level. When the levelness is poor, the buoyancy and initial angle of the test bearing section loaded with gravelly clay soil sample 2 are adjusted by inflating the air bladder group as a whole or partially.

[0113] The hollow test chamber 7 is equipped with a left-side propeller 3 and a right-side propeller 4 arranged in a centrally symmetrical manner on the left and right sides respectively. The left-side propeller 3 and the right-side propeller 4 push the front half 1-1 and the rear half 1-2 of the mold towards the center of the test device, respectively, to apply shear force to the gravelly clay sample 2. The hollow test chamber 7 is equipped with a front-side puller 5 and a rear-side puller 6 arranged in an axisymmetric manner on the front and rear sides respectively. The front-side puller 5 and the rear-side puller 6 pull the front half 1-1 and the rear half 1-2 of the mold towards the front and rear sides of the test device, respectively, to apply tensile force to the gravelly clay sample 2.

[0114] Furthermore, in the above technical solution, both the front half 1-1 and the rear half 1-2 of the mold include a bearing box composed of a lateral push plate 1-1-5, an axial pull plate 1-1-6, and a fixed base plate 1-1-7. The lateral push plate 1-1-5 and the axial pull plate 1-1-6 are respectively vertically fixed on the adjacent side walls of the fixed base plate 1-1-7. The middle parts of the lateral push plate 1-1-5 and the axial pull plate 1-1-6 are respectively provided with a lateral connection hole 1-2-0 and an axial connection hole 1-1-8. The two ends of the fixed base plate 1-1-7 away from the axial pull plate 1-1-6 are respectively provided with a first joint plate 1-1-1 and a second joint plate 1-1-2 distributed symmetrically, which are used to pre-make joints on the left and right sides of the soil sample. The first joint plate 1-1-1 and the second joint plate 1-1-2 are detachably installed with the fixed base plate 1-1-7.

[0115] The fixed base plate 1-1-7 has notches at both ends on one side. The first seam plate 1-1-1 and the second seam plate 1-1-2 are respectively embedded in the notches on both sides, and the thickness of the first seam plate 1-1-1 and the second seam plate 1-1-2 matches the depth of the notches. A gap is reserved between the first seam plate 1-1-1 and the second seam plate 1-1-2 on the same fixed base plate 1-1-7. The two sets of first seam plates 1-1-1 and second seam plates 1-1-2 on the front and rear fixed base plates 1-1-7 fit together.

[0116] In this embodiment, the thickness of the first seam control plate 1-1-1 and the second seam control plate 1-1-2 is 0.3mm. That is, when the two sets of the first seam control plates 1-1-1 and the second seam control plates 1-1-2 on the two fixed base plates 1-1-7 are attached to each other, the thickness of the prefabricated seam is 0.6mm.

[0117] Furthermore, in the above technical solution, the Z-shaped compaction plate 1-7 is made of aluminum alloy, and pressure plate gaps 1-7-1 are opened on both sides. The pressure plate gaps 1-7-1 are adapted to the shape of the two sets of first seam plates 1-1-1 and second seam plates 1-1-2 on the front and rear fixed base plates 1-1-7 after they are fitted together.

[0118] The Z-shaped compaction plate 1-7 is adapted to the shape of the front half 1-1 and the rear half 1-2 of the mold, so that it fits perfectly into the front half 1-1 and the rear half 1-2 of the mold.

[0119] The top of the Z-shaped compaction plate 1-7 is equipped with a handle 1-7-2, which makes it easy to remove the Z-shaped compaction plate 1-7 after the gravelly clay soil sample 2 has been compacted.

[0120] Furthermore, in the above technical solution, both the first joint plate 1-1-1 and the second joint plate 1-1-2 are provided with positioning blocks 1-1-3 and assembly blocks 1-1-4. The assembly block 1-1-4 is located on the lower side of the first joint plate 1-1-1 and the second joint plate 1-1-2, and is connected to the fixed base plate 1-1-7 by bolts. Whether the first joint plate 1-1-1 and the second joint plate 1-1-2 need to be removed depends on the progress of the test. When preparing the gravelly clay sample 2 and conducting tensile fracture tests, it is not necessary to remove the first joint plate 1-1-1 and the second joint plate 1-1-2. However, when conducting shear fracture tests, it is necessary to remove the first joint plate 1-1-1 and the second joint plate 1-1-2.

[0121] Positioning block 1-1-3 is located in the middle of the side of the first joint plate 1-1-1 and the second joint plate 1-1-2, and its surface has hook holes. During the shear fracture test, the first joint plate 1-1-1 and the second joint plate 1-1-2 need to be removed. With the combined block 1-1-4 disconnected from the support box, it serves as a lateral traction point to pull the sample from the gravelly clay sample 2. This can be achieved by hooking the positioning block 1-1-3 with pliers and pulling it out.

[0122] The rectangular ring wall 1-6 is made of a rectangular annular aluminum alloy ring. Positioning grooves are provided on both sides of the bottom. The positioning grooves are matched with the structure of the two sets of first seam plates 1-1-1 and second seam plates 1-1-2 on the front and rear fixed base plates 1-1-7. The inside of the rectangular ring wall 1-6 is fitted with the outside of the test bearing part, and after being fitted on the outside of the test bearing part, its top is flush with the test bearing part.

[0123] Furthermore, in the above technical solution, the three sides of the fixed base plate 1-1-7 are provided with first threaded holes 1-1-9, and the top of the front floating cavity 1-3 and the rear floating cavity 1-4 are provided with protrusions 1-3-3 that match the three sets of first threaded holes 1-1-9. The carrier box is snapped into the inner side of the three sets of protrusions 1-3-3 and fixedly connected to the front floating cavity 1-3 or the rear floating cavity 1-4 by bolts. The bolts penetrate the protrusions 1-3-3 and are screwed into the first threaded holes 1-1-9.

[0124] The front floating cavity 1-3 and the rear floating cavity 1-4 are provided with second threaded holes 1-3-1 at both ends of opposite sides. The front floating cavity 1-3 and the rear floating cavity 1-4 are fixedly connected by cavity connecting plate 1-5 and bolts. Cavity connecting plate 1-5 is a perforated aluminum alloy connecting plate. When connecting the front floating cavity 1-3 and the rear floating cavity 1-4, the bolts penetrate the cavity connecting plate 1-5 and enter the interior of the second threaded hole 1-3-1.

[0125] Furthermore, in the above technical solution, the airbag assembly 1-3-4 includes multiple airbags arranged in a rectangular array, made of rubber, and filled with hydrogen gas to ensure that the front floating chamber 1-3 and the rear floating chamber 1-4 float on the water surface.

[0126] Multiple airbags are separated by diaphragms with channels. Solenoid valves are embedded within these channels. Each airbag has an independent inflation / deflation port, allowing multiple airbags to be inflated and deflated synchronously, or allowing adjustment of the gas volume in a localized area of ​​the airbag. Figure 5 As shown in (a), when not inflated, the lower surfaces of the multiple air bladders are flush with the lower edges of the front floating cavities 1-3 and the rear floating cavities 1-4; Figure 5 As shown in (b), the surface of the airbag bulges out when inflated; Figure 5 As shown in (c), in addition to uniform inflation, the gas in the individual air bladders in the air bladder group 1-3-4 at the bottom of the front floating cavity 1-3 and the rear floating cavity 1-4 can be adjusted, thereby adjusting the floating angle of the front floating cavity 1-3 and the rear floating cavity 1-4 on the water surface, so that the two float horizontally on the water surface.

[0127] Furthermore, in the above technical solution, the outer wall of the hollow test tank 7 is provided with a water inlet hole 7-1 and a water outlet hole 7-2 that penetrate the groove, and the water inlet hole 7-1 and the water outlet hole 7-2 are used to replenish and replace the water in the groove, respectively.

[0128] Furthermore, in the above technical solution, the left propeller 3, the right propeller 4, the front puller 5 and the rear puller 6 are installed on the hollow test tank 7 through a lifting mechanism;

[0129] The left thruster 3 includes a left connecting part 3-1 and a left control part 3-2 for connecting to and controlling the extension and retraction of the output end of the left connecting part 3-1;

[0130] The right-side thruster 4 includes a right-side connecting part 4-1 and a right-side control part 4-2 for connecting to and controlling the extension and retraction of the output end of the right-side connecting part 4-1;

[0131] The front puller 5 includes a front connecting part 5-1 and a front control part 5-2 for connecting to and controlling the extension and retraction of the output end of the front connecting part 5-1;

[0132] The rear puller 6 includes a rear connecting part 6-1 and a rear control part 6-2 for connecting to and controlling the extension and retraction of the output end of the rear connecting part 6-1;

[0133] The output ends of the left connecting part 3-1 and the right connecting part 4-1 are respectively connected to the side connecting holes 1-2-0 on the two carrier boxes;

[0134] The output ends of the front connecting part 5-1 and the rear connecting part 6-1 are respectively connected to the axial connecting holes 1-1-8 on the two carrier boxes.

[0135] Based on the above structure, the heights of the left connecting part 3-1, the right connecting part 4-1, the front connecting part 5-1, and the rear connecting part 6-1 can be controlled, facilitating docking between devices; and pushing or pulling forces can be applied to the two carrier boxes respectively.

[0136] Furthermore, in the above technical solution, the left connecting part 3-1, the right connecting part 4-1, the front connecting part 5-1 and the rear connecting part 6-1 are all configured as telescopic drive mechanisms, which adopt at least one of cylinder, electric push rod, hydraulic cylinder and linear module.

[0137] Furthermore, in the above technical solution, displacement sensors and stress sensors are provided at the connecting ends of the left connecting part 3-1, the right connecting part 4-1, the front connecting part 5-1, and the rear connecting part 6-1, respectively, to sense the displacement and stress value of the left connecting part 3-1, the right connecting part 4-1, the front connecting part 5-1, and the rear connecting part 6-1 during the extension and retraction operation. Specifically, the collected data includes the displacement of the left connecting part 3-1 from left to right and the thrust it receives when the gravelly clay sample 2 is sheared and fractured, and the displacement of the right connecting part 4-1 from right to left and the thrust it receives; and the displacement of the front connecting part 5-1 from back to front and the tensile force it receives, and the displacement of the rear connecting part 6-1 from front to back and the tensile force it receives when the gravelly clay sample 2 is tensile and fractured.

[0138] The friction-free tensile-shear fracture test apparatus for gravelly clay in high-core wall dams provided by this invention is used as follows: Figure 8 As shown, where:

[0139] Figure 8 (a) shows the state after the front half 1-1 and the rear half 1-2 of the mold are joined together;

[0140] Figure 8 (b) shows that Figure 8 Based on (a), the state of assembling and compacting fracture mold 1;

[0141] Figure 8 (c) shows that Figure 8 Based on (b), prepare and compact gravelly clay soil sample 2;

[0142] Figure 8 (d) shows that Figure 8 Based on (c), the compaction fracture mold 1 is transferred to the groove on the hollow test tank 7;

[0143] Figure 8 (e) shows that Figure 8 Based on (d), the state of removing Z-shaped compaction plates 1-7 and rectangular ring walls 1-6;

[0144] Figure 8 (f) shows that in Figure 8 Based on (e), the test bearing part (compact fracture mold test part) is made to be suspended;

[0145] Figure 8 (g) shows that in Figure 8 Based on (f), the state of the fixed test bearing part (compaction fracture mold test part) is maintained;

[0146] Figure 8 (h) shows that in Figure 8Based on (g), the cavity connecting plates 1-5 are removed and the test is conducted.

[0147] Figure 8 (i) shows in Figure 8 Based on (h), until the gravelly clay sample 2 reaches the state of tensile fracture;

[0148] Figure 8 (j) shows that in Figure 8 Based on (f), the state of the fixed test bearing part (compaction fracture mold test part) is maintained;

[0149] Figure 8 (k) shows that in Figure 8 Based on (j), the cavity connecting plates 1-5 are removed and the test is conducted.

[0150] Figure 8 (l) shows that in Figure 8 Based on (k), until the gravelly clay sample 2 reaches the state of shear fracture.

[0151] The present invention provides the following embodiments:

[0152] The tensile-shear fracture test method for gravelly clay-mixed high-core wall dams without friction effects was adopted, and the specific steps are as follows:

[0153] S1. Determine the optimum moisture content and maximum dry density;

[0154] Specifically, before conducting fracture tests, it is necessary to determine the optimum moisture content and maximum dry density of gravelly clay in the material yard near the high-core wall dam site area under different gravel content. Referring to the specifications, a heavy compactor was selected to conduct compaction tests on the gravelly clay. The compaction hammer mass was 4.5 kg, the hammer base diameter was 51 mm, and the drop height was 457 mm. The optimum moisture content and maximum dry density of gravelly clay in the high-core wall dam site area at gravel content of 30%–50% are shown in Table 1.

[0155] Table 1. Optimal moisture content and maximum dry density of gravelly clay with gravel content of 30%–50%.

[0156]

[0157] S2, Design test conditions:

[0158] In studying the effect of moisture content on fracture properties, experiments were conducted at five levels: 10.34%, 9.87%, 9.43%, 9.08%, and 8.72%. In studying the effect of dry density on fracture properties, a value of 2.16 g / cm³ was chosen. 3 2.14 g / cm 3 2.11 g / cm 3 2.07 g / cm3 2.03 g / cm 3 Five levels of testing were conducted. When studying the effect of gravel content on fracture characteristics, five levels of testing were proposed: 30%, 35%, 40%, 45%, and 50%. At the same time, the test conditions were designed while keeping other variables constant.

[0159] S3, such as Figure 8 As shown in (a), the front half 1-1 and the rear half 1-2 of the combined mold are operated as follows:

[0160] S3.1, Front half of the combined mold 1-1;

[0161] Specifically, bolts are screwed into the assembly block 1-1-4 and the fixed base plate 1-1-7 on the first seam plate 1-1-1 from left to right, so that the first seam plate 1-1-1 is relatively fixed on the carrier box; bolts are screwed into the assembly block 1-1-4 and the fixed base plate 1-1-7 on the second seam plate 1-1-2 from right to left, so that the second seam plate 1-1-2 is relatively fixed on the carrier box, thereby making the first seam plate 1-1-1, the second seam plate 1-1-2 and the carrier box together form the front half of the mold 1-1.

[0162] S3.2, Rear half of the combined mold 1-2:

[0163] Using the same steps as in S3.1, another set of first seam cutting plate 1-1-1, second seam cutting plate 1-1-2 and carrier box are combined to form the rear half of the mold 1-2.

[0164] S4, such as Figure 8 As shown in (b), the compaction fracture mold 1 is assembled, and the specific operation is as follows:

[0165] S4.1 Connect the front half of the mold 1-1 to the front floating cavity 1-3 and the rear half of the mold 1-2 to the rear floating cavity 1-4;

[0166] Specifically, bolts are used to fix the three sets of protrusions 1-3-3 to the corresponding first threaded holes 1-1-9, thereby connecting the front half of the mold 1-1 to the front floating cavity 1-3. The same method is used to connect the rear half of the mold 1-2 to the rear floating cavity 1-4.

[0167] S4.2 Connect the front floating cavity 1-3 and the rear floating cavity 1-4 and fit the rectangular ring wall 1-6 on top;

[0168] Specifically, the front floating cavity 1-3 and the rear floating cavity 1-4 are fixedly connected using the cavity connecting plates 1-5 on the left and right sides. A certain amount of machine oil is applied to the inside of the rectangular ring wall 1-6 to ensure sufficient lubrication when in contact with the compaction fracture mold test part. Then, the rectangular ring wall 1-6 is nested on the outside of the compaction fracture mold test part, so that the three are tightly combined into one, forming the compaction fracture mold 1.

[0169] S5, such as Figure 8 As shown in (c), gravelly clay soil sample 2 was prepared and compacted, and the specific procedures are as follows:

[0170] S5.1 Calculate the required mass of water H, clay C, gravel G, and total mass Y of gravel-mixed clay using the mold volume V, i.e., Y = H + C + G.

[0171] S5.2 Add water of mass H to clay of mass C, place it in a sealed box and let it stand for 24 hours. Add gravel of mass G and stir quickly. Place it in a sealed box again and let it stand for 24 hours.

[0172] S5.3. The compaction fracture mold test section is added in N stages. After each addition of gravelly clay, the gravelly clay is compacted using Z-shaped compaction plates 1-7.

[0173] S6, such as Figure 8 As shown in (d), the compaction fracture mold 1 is transferred to the hollow test tank 7;

[0174] Specifically, the compacted gravelly clay sample 2, along with the compaction fracture mold 1, is placed into the hollow test chamber 7 using a hoisting rope. Since the hollow test chamber 7 is not filled with water, the compaction fracture mold 1 is in contact with the bottom of the hollow test chamber 7.

[0175] S7, such as Figure 8 As shown in (e), remove the Z-shaped compaction plate 1-7 and the rectangular ring wall 1-6;

[0176] Specifically, the Z-shaped compaction plate 1-7 above the gravelly clay sample 2 and the rectangular ring wall 1-6 fitted on the outside of the front half 1-1 and the rear half 1-2 of the mold are removed, but the cavity connecting plate 1-5 is still connected to the front half 1-1 and the rear half 1-2 of the mold. At this time, the front half 1-1 and the rear half 1-2 of the mold cannot be separated from each other.

[0177] S8, such as Figure 8 As shown in (f), the compaction fracture mold test section is suspended, and the specific operation is as follows:

[0178] S8.1. A certain amount of hydrogen is filled into the two sets of airbags 1-3-4 at the bottom of the front floating cavity 1-3 and the rear floating cavity 1-4, so that the front floating cavity 1-3 and the rear floating cavity 1-4 are lifted up by the bulge of the airbags 1-3-4.

[0179] S8.2 Open the water inlet hole 7-1 and close the water outlet hole 7-2. Fill the hollow test tank 7 with water. The compacted fracture mold test part will continue to float as the water level rises under the action of buoyancy.

[0180] S8.3 By changing the hydrogen content in the air bladders at different locations in the front floating cavity 1-3 and the rear floating cavity 1-4, the floating condition of the compaction fracture mold test section is adjusted, and the compaction fracture mold 1 is leveled by using the four horizontal air bubbles 1-3-2 on the front floating cavity 1-3 and the rear floating cavity 1-4.

[0181] Furthermore, in the above technical solution, the hydrogen filling amount of the two airbag groups 1-3-4 is obtained by calculation, and the steps are as follows:

[0182] S8.1.1 Collect the mass A of the compaction fracture mold test part and the mass Y of the gravel-mixed clay soil sample 2, and obtain the total mass of the test body composed of the compaction fracture mold test part and the gravel-mixed clay soil sample 2 as A+Y;

[0183] S8.1.1 By substituting A+Y into the following expression, the buoyancy F(buoyancy) corresponding to A+Y can be obtained;

[0184] A + Y = F(buoyancy) = G(displacement) = ρ(water)gV(displacement)

[0185] Where ρ(water) represents the density of the liquid filled into the hollow test tank 7, and g is the acceleration due to gravity, with a value of 9.8 m / s². 2 V (displacement) represents the volume of liquid displaced by the test subject, and G (displacement) represents the volume of water displaced when the test subject floats on the water surface against gravity.

[0186] We can deduce that:

[0187] V(displacement) = (A + Y) / ρ(water)g

[0188] S8.1.2 By substituting the volume V (displaced) of the liquid displaced when the test body floats into the following formula, the minimum mass M of hydrogen gas required for the test body to overcome gravity and float is calculated.

[0189] M = ρ(gas)V(discharge)

[0190] Where ρ(gas) represents the density of hydrogen gas, with a value of 0.089 g / m³. 3 .

[0191] Furthermore, in the above technical solution, the leveling method described in S8.3 is based on the structure of the airbag assembly, which includes multiple airbags arranged in a rectangular array for filling with hydrogen.

[0192] A diaphragm is provided between multiple airbags, and a channel is provided on the diaphragm. A solenoid valve is embedded in the channel. Each airbag is provided with an independent inflation and deflation port, so that multiple airbags can be inflated and deflated simultaneously or the amount of gas in the airbags in a local area can be adjusted.

[0193] The solenoid valve is electrically connected to a remote control chip, and the amount of hydrogen filled into the gasbag is increased or decreased by inputting the specific gasbag number through the remote control.

[0194] Furthermore, in the above technical solution, the inflation of the two airbag groups 1-3-4 has the following characteristics:

[0195] When the vertical position of the test subject on the water surface is finely adjusted, multiple solenoid valves open, allowing multiple airbags to communicate with each other, increasing the hydrogen mass P in any one airbag, and the hydrogen in the other airbags is replenished accordingly, thus adjusting the overall height of the test subject on the water surface.

[0196] When the solenoid valve between one of the airbags and its adjacent airbags fails to open due to signal control or malfunction, causing the airbag to be concave relative to its outer side, the solenoid valve on this airbag is opened, and the hydrogen mass in each of the other airbags is reduced by P / (n-1), where n is the number of airbags in each airbag group 1-3-4. For example, in this embodiment, both airbag groups 1-3-4 contain 32 airbags. When the compaction and fracture mold 1 needs to be leveled, increasing the hydrogen mass P in one airbag will reduce the hydrogen mass in each of the other airbags by P / 31.

[0197] When the test body is tilted and needs to be leveled, the solenoid valve is closed, and the hydrogen mass P of a certain airbag in the lower side area of ​​the compaction fracture mold 1 is increased. The increased hydrogen mass P is filled into the corresponding airbag from the external gas supply pipe.

[0198] At this point, the entire tensile-shear fracture test apparatus for gravelly clay core wall is assembled.

[0199] S9. Complete the assembly of the test apparatus and select the test type:

[0200] If a tensile fracture test is to be performed, proceed to S9.1; if a shear fracture test is to be performed, proceed to S9.2.

[0201] S9.1 Conduct tensile fracture tests on gravelly clay core walls:

[0202] 1. The procedure for the tensile fracture test of gravelly clay sample 2 is as follows:

[0203] S9.1.1, such as Figure 8 As shown in (g), the test section with a fixed compaction fracture mold:

[0204] By controlling the front control unit 5-2 and the rear control unit 6-2, the output ends of the front connecting part 5-1 and the rear connecting part 6-1 are extended and gradually brought closer to the axial connecting hole 1-1-8 in front and the lateral connecting hole 1-2-0 in the rear. The hydrogen content filled inside the two sets of airbags 1-3-4 is finely adjusted so that the axial connecting hole 1-1-8 and the lateral connecting hole 1-2-0 are at the same height as the front connecting part 5-1 and the rear connecting part 6-1, respectively. The front connecting part 5-1 and the rear connecting part 6-1 are extended again until they are fixedly connected to the compaction fracture mold test part.

[0205] S9.1.2, such as Figure 8 As shown in (h), remove cavity connecting plates 1-5 and conduct tests:

[0206] Remove the cavity connecting plates 1-5 that connect the front floating cavity 1-3 and the rear floating cavity 1-4 and are located on the left and right sides, and open the front control unit 5-2 and the rear control unit 6-2. Pull the front connecting part 5-1 and the rear connecting part 6-1 at a certain rate; record the data measured by the stress and displacement sensors connected to the front connecting part 5-1 and the rear connecting part 6-1.

[0207] S9.1.3, such as Figure 8 As shown in (i), until the gravelly clay sample 2 underwent tensile fracture and the data was processed:

[0208] The stress and displacement were recorded until the gravelly clay sample 2 underwent tensile fracture. The stress and displacement data were then processed to obtain the stress F (tensile) and displacement L (tensile) experienced by the gravelly clay sample 2 during the tensile fracture test, as expressed below:

[0209] F(pull) = (F5|+|F6) / 2

[0210] L(pull) = (L5|+|L6) / 2

[0211] Wherein, F5 and F6 represent the stress data recorded in the front connecting part 5-1 and the rear connecting part 6-1, respectively; L5 and L6 represent the displacement data recorded in the front connecting part 5-1 and the rear connecting part 6-1, respectively.

[0212] Based on the values ​​of F (tensile) and L (tensile), the stress-strain curve of the gravelly clay sample 2 under tensile fracture was obtained. The characteristic parameters of the gravelly clay in the high core wall dam under tensile fracture process were analyzed by the stress-strain curve of tensile fracture. The characteristic parameters include fracture toughness and fracture energy. Thus, the tensile fracture characteristics of the gravelly clay sample 2 of the high core wall dam were fully understood.

[0213] Furthermore, in the above technical solution, the pulling rates of the front connecting part 5-1 and the rear connecting part 6-1 are set to multiple levels to study the influence of different loading rates on the tensile fracture characteristics of the gravelly clay sample 2. For example, setting multiple levels as level 1 (0.005 mm / s), level 2 (0.01 mm / s), level 3 (0.02 mm / s), level 4 (0.05 mm / s), and level 5 (0.1 mm / s) can simulate the stress conditions of the gravelly clay at different heights of the core wall of the high core wall dam during the construction and operation periods. Since the core wall dam is relatively high, the uneven settlement of the gravelly clay in the lower part of the core wall is relatively small, so level 1 or level 2 can be used for the test; the uneven settlement of the gravelly clay in the higher part of the core wall is relatively large, so level 4 or level 5 can be used for the test.

[0214] It should be noted that when the front connecting part 5-1 and the rear connecting part 6-1 are each at level 1 (0.005 mm / s), since the tension is applied simultaneously from both sides, the loading rate studied for the effect on the tensile fracture characteristics of gravelly clay is 0.01 mm / s. The same applies to other levels.

[0215] S9.2 Conduct shear fracture tests on gravelly clay core:

[0216] 2. The procedure for the shear fracture test of gravelly clay sample 2 is as follows:

[0217] S9.2.1, such as Figure 8 As shown in (j), the test section with a fixed compaction fracture mold:

[0218] By controlling the left control unit 3-2 and the right control unit 4-2 to extend the output ends of the left connecting part 3-1 and the right control unit 4-2 respectively, they gradually approach the axial connecting hole 1-1-8 on the left and the lateral connecting hole 1-2-0 on the right. The hydrogen content filled inside the two sets of airbags 1-3-4 is finely adjusted so that the axial connecting hole 1-1-8 and the lateral connecting hole 1-2-0 are at the same height as the left connecting part 3-1 and the right connecting part 4-1 respectively. The left connecting part 3-1 and the right connecting part 4-1 are then extended again until they are fixedly connected to the compaction fracture mold test part.

[0219] S9.2.2, such as Figure 8 As shown in (k), remove cavity connecting plates 1-5 to expose the prefabricated seam and conduct a test:

[0220] Remove the cavity connecting plates 1-5 that connect the front floating cavity 1-3 and the rear floating cavity 1-4 and are located on their left and right sides. With the assembly block 1-1-4 disconnected from the carrier box, simultaneously use hook pliers to hook into the hook holes on the positioning blocks 1-1-3 on both sides, and remove the first seam plate 1-1-1 and the second seam plate 1-1-2 respectively. Open the left control unit 3-2 and the right control unit 4-2, and advance the left connecting part 3-1 and the right connecting part 4-1 at a certain rate. Record the stress and displacement sensor data inside the left connecting part 3-1 and the right connecting part 4-1.

[0221] S9.2.3, such as Figure 8 As shown in (l), until the gravelly clay sample 2 underwent shear fracture and the data was processed:

[0222] The stress and displacement were recorded until the gravelly clay sample 2 underwent shear fracture. The stress and displacement data were then processed to obtain the stress F (shear) and displacement L (shear) experienced by the gravelly clay sample 2 during the shear fracture test, expressed as follows:

[0223] F(shear) = (|F3| + |F4|) / 2

[0224] L(shear) = (|L3| + |L4|) / 2

[0225] Wherein, F3 and F4 represent the stress data recorded in the left connecting part 3-1 and the right connecting part 4-1, respectively; L3 and L4 represent the displacement data recorded in the left connecting part 3-1 and the right connecting part 4-1, respectively.

[0226] Based on the F (shear) and L (shear) values, the stress-strain curve of the gravelly clay sample 2 under shear fracture was obtained. The characteristic parameters of the gravelly clay in the high core wall dam under shear fracture process were analyzed by the stress-strain curve of shear fracture. The characteristic parameters include fracture toughness and fracture energy. Thus, the shear fracture characteristics of the gravelly clay sample 2 in the high core wall dam were fully understood.

[0227] Furthermore, in the above technical solution, the advancement rates of the left connecting part 3-1 and the right connecting part 4-1 are set to multiple levels to study the influence of different loading rates on the shear fracture characteristics of the gravelly clay sample 2. For example, multiple levels can be set as level 1 (0.005 mm / s), level 2 (0.01 mm / s), level 3 (0.02 mm / s), level 4 (0.05 mm / s), and level 5 (0.1 mm / s), which can simulate the stress conditions of the gravelly clay at different heights of the core wall of the high-core dam during construction and operation. Because the core wall dam is relatively high, the uneven settlement of the gravelly clay in the lower and middle parts of the core wall is relatively small, so level 1 or level 2 can be used for the test; the uneven settlement of the gravelly clay in the higher and middle parts of the core wall is relatively large, so level 4 or level 5 can be used for the test.

[0228] It should be noted that when the left connecting part 3-1 and the right connecting part 4-1 are each at level 1 (0.005 mm / s), since they are advanced simultaneously, the loading rate studied for the effect on the shear fracture characteristics of gravelly clay is 0.01 mm / s. The same applies to other levels.

[0229] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A method for tensile-shear fracture testing of gravelly clay in high-core wall dams without frictional influence, characterized in that: Includes the following steps: S1. Collect soil samples and determine their optimum moisture content and maximum dry density under different gravel content; S2. Design experiments under various working conditions to study the effects of moisture content, dry density, and gravel content on fracture characteristics, including: A) Take soil samples with the same dry density and gravel content and divide them into multiple portions. Adjust each portion of soil sample to different moisture content levels to study the effect of moisture content on fracture characteristics. B) Take soil samples with the same moisture content and gravel content and divide them into multiple portions. Adjust each portion of soil sample to different dry density levels to study the effect of dry density on fracture characteristics. C) Take soil samples with the same dry density and moisture content and divide them into multiple portions. Adjust each portion of soil sample to different gravel content levels to study the effect of gravel content on fracture characteristics. S3, Combining the front half (1-1) and rear half (1-2) of the mold: Using the same steps, bolts are screwed into the combination block (1-1-4) and the fixed base plate (1-1-7) on the first seam plate (1-1-1) and the second seam plate (1-1-2) in sequence, fixing the first seam plate (1-1-1) and the second seam plate (1-1-2) relative to each other on the carrier box, so that the two sets of first seam plates (1-1-1), second seam plates (1-1-2) and carrier box together form the front half (1-1) and rear half (1-2) of the mold with the same structure; S4. Assemble the compaction fracture mold (1): The front half (1-1) and the rear half (1-2) of the mold are placed symmetrically at the center. The three sets of protrusions (1-3-3) are fixedly connected to the corresponding first threaded holes (1-1-9) using bolts, and are installed on the front floating cavity (1-3) and the rear floating cavity (1-4) respectively. The front floating cavity (1-3) and the rear floating cavity (1-4) are fixedly connected using cavity connecting plate (1-5) to form the compaction fracture mold test part. A rectangular ring wall (1-6) is fitted on its outer side to assemble it into a compaction fracture mold (1). S5. Prepare and compact gravelly clay soil samples (2): The gravelly clay sample prepared in S2 was added into the compaction fracture mold (1) assembled in S4 and compacted using Z-shaped compaction plates (1-7) to obtain the gravelly clay sample (2). S6. Transfer the compaction fracture mold to the hollow test chamber (7); S7. Remove the Z-shaped compaction plate (1-7) and the rectangular ring wall (1-6), while keeping the cavity connecting plate (1-5) connected to the front half (1-1) and the rear half (1-2) of the mold. S8. Suspend the compaction fracture mold test section until its bottom separates from the bottom wall of the hollow test tank (7) and is in a frictionless state. The process is as follows: S8.

1. Hydrogen gas is filled into the two sets of airbags (1-3-4) at the bottom of the front floating cavity (1-3) and the rear floating cavity (1-4) to lift the front floating cavity (1-3) and the rear floating cavity (1-4). S8.2 Open the water inlet hole (7-1) and close the water outlet hole (7-2), fill the groove of the hollow test tank (7) with water, so that the compaction fracture mold test part floats continuously as the water level rises under the action of buoyancy; S8.

3. By changing the hydrogen content in the airbags at different locations on the two airbag groups (1-3-4), the compaction fracture mold test section is leveled. S9. The test apparatus is assembled and the tests are carried out, including tensile fracture test S9.1 and shear fracture test S9.

2. S9.1 Conduct tensile fracture tests on gravelly clay core walls: For the test section of the compaction fracture mold, the cavity connecting plate (1-5) was removed. The front puller (5) and the rear puller (6) pulled the front half (1-1) and the rear half (1-2) of the mold to the sides respectively. The stress and displacement sensor measurement data at the connection end were recorded. The test was stopped when the gravel-coated clay sample (2) underwent tensile fracture. The stress-strain curve of the gravel-coated clay sample (2) under tensile fracture was obtained. The tensile fracture characteristics of the gravel-coated clay sample (2) of the high core wall dam were analyzed. S9.2 Conduct shear fracture tests on gravelly clay core: For the test section of the compaction fracture mold, the cavity connecting plate (1-5), the first seam plate (1-1-1), and the second seam plate (1-1-2) are removed. The left pusher (3) and the right pusher (4) push the front half (1-1) and the rear half (1-2) of the mold to the center of the test device respectively. The stress and displacement sensor measurement data at the connection end are recorded. The test is stopped when the gravel-coated clay sample (2) undergoes shear fracture. The stress-strain curve of the shear fracture of the gravel-coated clay sample (2) is obtained. The shear fracture characteristics of the gravel-coated clay sample (2) of the high core wall dam are analyzed.

2. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence as described in claim 1, characterized in that: In S1, the soil sample was gravelly clay from the material yard near the site of the high core wall dam. A heavy compactor was used to conduct a gravelly clay compaction test to obtain the optimal moisture content and maximum dry density of the gravelly clay sample with a gravel content of 30% to 50%.

3. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence as described in claim 1, characterized in that: In S2, A) When designing the test conditions, under the condition that other variables remain constant, the proposed range of soil sample moisture content is set to 8.72% to 10.34%. B) When designing the test conditions, with other variables kept constant, the proposed range for the dry density of the soil sample was set at 2.03 g / cm³. 3 ~16g / cm 3 ; C) When designing the test conditions, while keeping other variables constant, the proposed range for the amount of gravel in the soil sample is set to 30%–50%.

4. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence as described in claim 1, characterized in that: The specific operating steps for processing the gravelly clay soil sample (2) in S5 are as follows: S5.1 Calculate the required mass of water H, clay C, gravel G, and total mass Y of gravel-mixed clay using the mold volume V, i.e., Y = H + C + G. S5.2 Add water of mass H to clay of mass C, place it in a sealed box and let it stand for 24 hours. Add gravel of mass G and stir quickly. Place it in a sealed box again and let it stand for 24 hours. S5.

3. Add the gravelly clay prepared in S5.2 to the compaction fracture mold test section in N portions. After each addition of gravelly clay, immediately compact the gravelly clay using a Z-shaped compaction plate (1-7).

5. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence according to claim 1, characterized in that: The hydrogen filling amount of the two airbag groups (1-3-4) in S8.1 was calculated, and the steps are as follows: S8.1.

1. Collect the mass A of the compaction fracture mold test part and the mass Y of the gravel-mixed clay soil sample (2) to obtain the total mass of the test body composed of the compaction fracture mold test part and the gravel-mixed clay soil sample (2) as A+Y; S8.1.1 By substituting A+Y into the following expression, the buoyancy F(buoyancy) corresponding to A+Y can be obtained; A + Y = F(buoyancy) = G(displacement) = ρ(water)gV(displacement) Where ρ(water) represents the density of the liquid filled into the hollow test tank (7), and g is the gravitational acceleration, with a value of 9.8 m / s². 2 V (displacement) represents the volume of liquid displaced by the test subject, and G (displacement) represents the volume of water displaced when the test subject floats on the water surface against gravity. We can deduce that: V(displacement) = (A + Y) / ρ(water)g S8.1.2 By substituting the volume V (displaced) of the liquid displaced when the test body floats into the following formula, the minimum mass M of hydrogen gas required for the test body to overcome gravity and float is calculated. M = ρ(gas)V(discharge) Where ρ(gas) represents the density of hydrogen gas, with a value of 0.089 g / m³. 3 .

6. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence according to claim 1, characterized in that: The leveling method in S8.3 is based on the structure of the airbag assembly (1-3-4), which includes multiple airbags arranged in a rectangular array for filling with hydrogen. A diaphragm is provided between multiple airbags, and a channel is provided on the diaphragm. A solenoid valve is embedded in the channel. Each airbag is provided with an independent inflation and deflation port, so that multiple airbags can be inflated and deflated simultaneously or the amount of gas in the airbags in a local area can be adjusted. The solenoid valve is electrically connected to a remote control chip, and the amount of hydrogen filled into the gasbag is increased or decreased by inputting the specific gasbag number through the remote control.

7. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence as described in claim 6, characterized in that: When inflating the two airbag groups (1-3-4), the following situation occurs: When the vertical position of the test subject on the water surface is finely adjusted, multiple solenoid valves open, allowing multiple airbags to communicate with each other, increasing the hydrogen mass P in any one airbag, and the hydrogen in the other airbags is replenished accordingly, thus adjusting the overall height of the test subject on the water surface. When the solenoid valve between one of the airbags and the adjacent airbag fails to open due to signal control or malfunction, causing it to be concave relative to the outside, the solenoid valve on this airbag is opened, and the hydrogen mass in each of the other airbags is reduced by P / (n-1) accordingly, where n is the number of airbags in each airbag group (1-3-4). When the test body is tilted, it needs to be leveled. The solenoid valve is closed, and the hydrogen mass P of a certain airbag in the lower side area of ​​the compaction fracture mold (1) is increased. The increased hydrogen mass P is filled into the corresponding airbag from the external gas supply pipe.

8. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence according to claim 1, characterized in that: In S9.1, the tensile fracture test procedure for gravelly clay sample (2) is as follows: S9.1.1, Fixed Compaction Fracture Mold Test Section: By controlling the front control unit (5-2) and the rear control unit (6-2), the output ends of the front connecting part (5-1) and the rear connecting part (6-1) are extended and gradually brought closer to the axial connecting hole (1-1-8) at the front and the lateral connecting hole (1-2-0) at the rear. The hydrogen content filled inside the two sets of airbags (1-3-4) is finely adjusted so that the axial connecting hole (1-1-8) and the lateral connecting hole (1-2-0) are at the same height as the front connecting part (5-1) and the rear connecting part (6-1), respectively. The front connecting part (5-1) and the rear connecting part (6-1) are extended again until they are fixedly connected to the compaction fracture mold test part. S9.1.2 Remove the cavity connecting plate (1-5) and conduct the test: Remove the cavity connecting plates (1-5) that connect the front floating cavity (1-3) and the rear floating cavity (1-4) and are located on the left and right sides, and open the front control unit (5-2) and the rear control unit (6-2). Pull the front connecting part (5-1) and the rear connecting part (6-1) at a certain rate; record the stress and displacement sensor data of the connection between the front connecting part (5-1) and the rear connecting part (6-1); S9.1.3, until the gravelly clay sample (2) undergoes tensile fracture and the data is processed: The stress and displacement were recorded until the gravelly clay sample (2) underwent tensile fracture. The stress and displacement data were then processed to obtain the stress F (tensile) and displacement L (tensile) experienced by the gravelly clay sample (2) during the tensile fracture test. The expressions are as follows: F(pull) = (|F5| + |F6|) / 2 L(pull) = (|L5| + |L6|) / 2 Wherein, F5 and F6 represent the stress data recorded at the front connecting part (5-1) and the rear connecting part (6-1), respectively; L5 and L6 represent the displacement data recorded at the front connecting part (5-1) and the rear connecting part (6-1), respectively. Based on the values ​​of F (tension) and L (tension), the stress-strain curve of the gravelly clay soil sample (2) under tensile fracture was obtained; the characteristic parameters of the gravelly clay soil in the high core wall dam under tensile fracture process were analyzed by the stress-strain curve of tensile fracture, including fracture toughness and fracture energy; thus, the tensile fracture characteristics of the gravelly clay soil sample (2) of the high core wall dam were fully understood.

9. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence according to claim 1, characterized in that: In S9.2, the procedure for the shear fracture test of gravelly clay sample (2) is as follows: S9.2.1, Fixed Compaction Fracture Mold Test Section: By controlling the left control unit (3-2) and the right control unit (4-2), the output ends of the left connecting part (3-1) and the right control unit (4-2) are extended and gradually brought closer to the axial connecting hole (1-1-8) on the left and the lateral connecting hole (1-2-0) on the right. The hydrogen content filled inside the two sets of airbags (1-3-4) is finely adjusted so that the axial connecting hole (1-1-8) and the lateral connecting hole (1-2-0) are at the same height as the left connecting part (3-1) and the right connecting part (4-1), respectively. The left connecting part (3-1) and the right connecting part (4-1) are extended again until they are fixedly connected to the compaction fracture mold test part. S9.2.2 Remove the cavity connecting plate (1-5) to expose the prefabricated joint and conduct a test: Remove the cavity connecting plates (1-5) that connect the front floating cavity (1-3) and the rear floating cavity (1-4) and are located on their left and right sides. With the assembly block (1-1-4) disconnected from the carrier box, simultaneously use pliers to hook the hook holes on the positioning blocks (1-1-3) on both sides and remove the first seam plate (1-1-1) and the second seam plate (1-1-2) respectively. Open the left control unit (3-2) and the right control unit (4-2) and advance the left connecting part (3-1) and the right connecting part (4-1) at a certain rate. Record the stress and displacement sensor data inside the left connecting part (3-1) and the right connecting part (4-1). S9.2.3, until the gravelly clay sample (2) undergoes shear fracture and the data is processed: The stress and displacement were recorded until the gravelly clay sample (2) underwent shear fracture. The stress and displacement data were then processed to obtain the stress F (shear) and displacement L (shear) experienced by the gravelly clay sample (2) during the shear fracture test. The expressions are as follows: F(shear) = (|F3| + |F4|) / 2 L(shear) = (|L3| + |L4|) / 2 Wherein, F3 and F4 represent the stress data recorded at the left connecting part (3-1) and the right connecting part (4-1), respectively; L3 and L4 represent the displacement data recorded at the left connecting part (3-1) and the right connecting part (4-1), respectively. Based on the F (shear) and L (shear) values, the stress-strain curve of the gravelly clay soil sample (2) during shear fracture was obtained; the characteristic parameters of the gravelly clay soil in the high core wall dam during shear fracture were analyzed by the stress-strain curve of shear fracture, including fracture toughness and fracture energy; thus, the shear fracture characteristics of the gravelly clay soil sample (2) of the high core wall dam were fully understood.

10. The method for tensile-shear fracture test of gravelly clay in high-core wall dams without frictional influence according to claim 1, characterized in that: The pulling rates of the front connecting part (5-1) and the rear connecting part (6-1) are set to multiple levels to study the effect of different loading rates on the tensile fracture characteristics of the gravelly clay soil sample (2). The advancement rates of the left connecting part (3-1) and the right connecting part (4-1) are set to multiple levels to study the influence of different loading rates on the shear fracture characteristics of the gravelly clay soil sample (2).

Images