Friction-influence-free high-core wall dam gravel-doped clay tensile-shear fracture test method

Abstract

The invention discloses a high-core wall dam gravel-doped clay tensile-shear fracture test method without friction influence. The method comprises the following steps: S1, collecting a soil sample and measuring the optimal moisture content and the maximum dry density; s2, designing a plurality of test working conditions; s3, the die front half part and the die rear half part are combined; s4, the compaction fracture mold is assembled; s5, preparing and compacting a gravel-doped clay sample; s6, transferring the compaction fracture mold to a hollow test tank; s7, the Z-shaped compaction plate and the rectangular ring wall are removed; s8, suspending the test part of the compaction fracture mold; and S9, carrying out a tensile fracture test or a shear fracture test on the core-wall gravel-doped clay. According to the test method, the tensile fracture and shear fracture characteristics of the gravel-doped clay can be researched on the same test device, and friction does not need to be considered. The problem that an existing soil body fracture test method cannot be used for measuring the fracture characteristics of the gravel-doped clay of the high-core wall dam is fundamentally solved, and the blank of the test method for the gravel-doped clay of the high-core wall dam is filled up.

Description

Technical Field

[0001] The invention relates to the field of geotechnical tests and designs a fracture characteristic test method for gravel-mixed clay in a high core dam, in particular to a tensile-shear fracture test method for gravel-mixed clay in a high core dam without friction influence. Background Art

[0002] In the planning and construction of high dams, earth-rock dams account for an increasingly high proportion due to their good foundation adaptability and economical construction materials. my country has the largest number of earth-rock high core wall rockfill dams, and most of them are concentrated in the southwest of China. According to statistics, the core wall dams in service in my country with a height of more than 100.0m include Shiziping (136.0m), Xiaolangdi (160.0m), Pubugou (186.0m), Nuozadu (261.5m) and Lianghekou (295.0m). The 300m-class core wall dams under construction and planned include Rumei (315.0m), Gushui (305.0m), Rimen (346.0m) and Qizong (356.0m).

[0003] Traditional low-medium earth-rock dams often use compacted pure clay core walls as an anti-seepage system. However, with the increase in construction height, the disadvantage of poor compressive performance of clay has gradually become prominent. The uneven settlement of the core wall and the rockfill body will cause cracks in the core wall clay. High core wall dams often add gravel into the core wall to improve the compressive performance of the anti-seepage core wall and reduce uneven settlement. The essence of core wall cracks is shear failure, tension failure or shear-tension composite failure caused by the stress and strain of the soil exceeding its tensile strength or shear strength. At present, there are few results related to the fracture characteristics of gravel-mixed clay in the core wall. Therefore, it is of great engineering significance and practical value to study the fracture characteristics of gravel-mixed clay and explore the evolution law of gravel-mixed clay cracks.

[0004] At present, soil fracture test devices are mostly focused on studying the fracture characteristics of clay or sand, and there is still a lack of test devices that can be used to study the fracture characteristics of gravel-mixed clay in high core dams. Based on the fact that the soil fracture test methods with many existing soil fracture test devices cannot be used to determine the fracture characteristics of gravel-mixed clay in high core dams, it is necessary to develop a tensile-shear fracture test method suitable for gravel-mixed clay in high core dams in the southwest region to fill the gap in the test method of gravel-mixed clay in high core dams. Summary of the invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned existing test technologies and provide a friction-free tensile-shear fracture test method for gravel-mixed clay in high core dams, which can measure both the tensile fracture properties and the shear fracture properties of gravel-mixed clay, thus filling the gap in the fracture property test method for gravel-mixed clay in high core dams.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] The tensile-shear fracture test method of gravel-mixed clay in high core dam without friction effect includes the following steps:

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

[0009] S2. Design and test 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 parts. Adjust each 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 parts. Adjust each 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 water content and divide them into multiple parts. Adjust each soil sample to different gravel content levels to study the effect of gravel content on fracture characteristics;

[0013] S3, Combine the front half of the mold and the back half of the mold:

[0014] In the same steps, bolts are used to screw into the combination blocks on the first seam-making plate and the second seam-making plate and the fixing bottom plate in sequence, and the first seam-making plate and the second seam-making plate are relatively fixed on the carrying box, so that the two sets of the first seam-making plate, the second seam-making plate and the carrying box together form the front half and the back half of the mold with the same structure;

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

[0016] The front half of the mold and the rear half of the mold are placed symmetrically in the center, and the three groups of protrusions are fixedly connected to the corresponding first threaded holes using bolts, and are respectively installed on the front floating cavity and the rear floating cavity; the front floating cavity and the rear floating cavity are fixedly connected using a cavity connecting plate to form a compaction fracture mold test part; a rectangular ring wall is sleeved on the outer side thereof to assemble into a compaction fracture mold;

[0017] S5. Preparation and compaction of gravel-mixed clay soil samples:

[0018] The gravel-mixed clay soil sample prepared in S2 is added into the compaction fracture mold assembled in S4, and compacted using a Z-shaped compaction plate to obtain a gravel-mixed clay soil sample;

[0019] S6. Transfer the compaction fracture mold to the hollow test tank; during the transfer, the compacted gravel-mixed clay soil sample 2 together with the compaction fracture mold 1 is placed into the hollow test tank 7 through a hanging rope. Since the hollow test tank 7 is not filled with water, the compaction fracture mold 1 is in contact with the bottom of the hollow test tank 7.

[0020] S7, removing the Z-shaped compacting plate and the rectangular ring wall, while still keeping the cavity connecting plate connected to the front half of the mold and the rear half of the mold;

[0021] S8, suspending the compacted fracture mold test part until its bottom is separated from the bottom wall of the hollow test tank and is in a friction-free state, the process is as follows:

[0022] S8.1. Inflate the two airbag groups at the bottom of the front floating cavity and the rear floating cavity with hydrogen to lift the front floating cavity and the rear floating cavity;

[0023] S8.2. Open the water inlet hole and close the water outlet hole, and fill the groove of the hollow test tank with water, so that the compacted fracture mold test part continues to float up as the water surface rises under the action of buoyancy;

[0024] S8.3. Level the compaction fracture mold test portion by changing the hydrogen content in the airbags at different locations on the two airbag groups;

[0025] S9. After the test apparatus is assembled, the test is performed, including the tensile fracture test S9.1 and the shear fracture test S9.2;

[0026] S9.1. Conduct tensile fracture test on core wall gravel-mixed clay:

[0027] The compaction fracture mold test part was fixed, the cavity connection plate was removed, and the front and rear pullers pulled the front and rear halves of the mold to both sides respectively, and the stress and displacement sensor measurement data at the connection ends were recorded. The test was stopped when the gravel-mixed clay sample was tensile fractured, and the stress-strain curve of the tensile fracture of the gravel-mixed clay sample was obtained, and the tensile fracture characteristics of the gravel-mixed clay sample of the high core wall dam were analyzed.

[0028] S9.2. Carry out shear fracture test on core wall with gravel-mixed clay:

[0029] The compaction fracture test part of the mold was fixed, the cavity connecting plate, the first seam-making plate and the second seam-making plate were removed, and the left and right thrusters pushed the front half and the rear half of the mold toward the center of the test device respectively. The stress and displacement sensor measurement data at the connection ends were recorded, and the test was stopped when the gravel-mixed clay sample underwent shear fracture. The stress-strain curve of the shear fracture of the gravel-mixed clay sample was obtained, and the shear fracture characteristics of the gravel-mixed clay sample of the high core wall dam were analyzed.

[0030] Preferably, in S1, the soil sample is gravel-mixed clay in the material yard near the dam site of the high core dam, and a heavy-duty compactor is selected to carry out a compaction test of the gravel-mixed clay to obtain the optimal moisture content and maximum dry density of the gravel-mixed clay soil sample at a gravel content of 30% to 50%.

[0031] Preferably, in S2, A) when designing the test conditions, the proposed range of soil sample moisture content is set to 8.72% to 10.34% while keeping other variables unchanged;

[0032] B) When designing the test conditions, the proposed range of soil sample dry density is set to 2.03 g / cm2 while keeping other variables unchanged. 3 ~16g / cm 3 ;

[0033] C) When designing the test conditions, the proposed range of the gravel content of soil samples is set to 30% to 50% while keeping other variables unchanged.

[0034] Preferably, when processing the gravel-mixed clay soil sample in S5, the specific operation steps are as follows:

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

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

[0037] S5.3. Add the gravel-mixed clay prepared in S5.2 into the compaction fracture mold test part N times. After each addition of the gravel-mixed clay, use a Z-shaped compaction plate to compact the gravel-mixed clay immediately.

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

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

[0040] S8.1.1. Substitute A+Y into the following expression and solve for the buoyancy F(buoyancy) corresponding to A+Y;

[0041] A+Y=F(float)=G(discharge)=ρ(water)gV(discharge)

[0042] Among them, ρ(water) represents the density of the liquid filled in the hollow test tank, and g is the acceleration due to gravity, which is 9.8m / s 2, V(displaced) represents the volume of liquid displaced by the test subject, and G(displaced) represents the displacement of the test subject when it floats on the water surface against gravity;

[0043] The inference is:

[0044] V(row)=(A+Y) / ρ(water)g

[0045] S8.1.2. Substitute the volume V(displaced) of the liquid displaced by the test subject when it floats into the following formula to calculate the minimum mass M of hydrogen that needs to be filled into the test subject to overcome gravity and achieve floating;

[0046] M=ρ(gas)V(exhaust)

[0047] Among them, ρ(gas) represents the density of hydrogen, which is 0.089g / m 3 .

[0048] Preferably, the leveling method described in S8.3 is implemented based on the structure of the airbag group, which includes a plurality of airbags distributed in a rectangular array for filling with hydrogen;

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

[0050] The connection end of the solenoid valve is electrically connected to a remote control chip, and the number of a specific airbag is input through the remote control to increase or decrease the amount of hydrogen filled therein.

[0051] Preferably, the two airbag groups are inflated in the following manner:

[0052] When the upper and lower positions of the test body on the water surface are finely adjusted, multiple solenoid valves are opened to allow multiple airbags to communicate with each other, and the hydrogen mass P in any airbag is increased, and the hydrogen in other airbags is supplemented accordingly, and the overall height of the test body on the water surface is adjusted up and down;

[0053] When the solenoid valve between one of the airbags and the adjacent airbag fails to open due to signal control or failure, causing it to be concave relative to the outside, the solenoid valve on this airbag is controlled to open, and the mass of hydrogen in each of the other airbags is correspondingly reduced by P / (n-1), 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, the hydrogen mass P of a certain airbag in the lower side area of ​​the compaction fracture mold 1 is increased, and the increased hydrogen mass P is filled into the corresponding airbag from the external gas transmission pipe.

[0055] Preferably, in S9.1, the tensile fracture test operation process for the gravel-mixed clay soil sample is as follows:

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

[0057] By controlling the front control part and the rear control part to extend the output ends of the front connection part and the rear connection part respectively, gradually close to the front axial connection hole and the rear lateral connection hole, fine-tune the hydrogen content filled in the two groups of airbag groups, make the axial connection hole and the lateral connection hole respectively consistent with the height of the front connection part and the rear connection part, and extend the front connection part and the rear connection part again until they are fixedly connected with the compaction fracture mold test part;

[0058] S9.1.2. Remove the cavity connection plate and conduct the test:

[0059] Remove the cavity connection plates connecting the front floating cavity and the rear floating cavity and located on the left and right sides, open the front control unit and the rear control unit, pull the front connection unit and the rear connection unit at a certain rate; record the data measured by the stress and displacement sensors connected to the front connection unit and the rear connection unit;

[0060] S9.1.3. Until the gravel-mixed clay sample undergoes tensile fracture and the data are processed:

[0061] The stress and displacement are recorded until the gravel-mixed clay soil sample undergoes tensile fracture. The stress and displacement data are then processed to obtain the stress F (tensile) and displacement L (tensile) of the gravel-mixed clay soil sample in the tensile fracture test. The expressions are 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 connecting part and the rear connecting part respectively; L5 and L6 represent the displacement data recorded at the front connecting part and the rear connecting part respectively;

[0065] According to the F (tensile) and L (tensile) values, the stress-strain curve of the tensile fracture of the gravel-mixed clay sample was obtained. The characteristic parameters of the gravel-mixed clay in the high core dam during the tensile fracture process were analyzed through the tensile fracture stress-strain curve, and the characteristic parameters included fracture toughness and fracture energy. Thus, the tensile fracture characteristics of the gravel-mixed clay sample in the high core dam were fully understood.

[0066] Preferably, in S9.2, the shear fracture test operation process for the gravel-mixed clay soil sample is as follows:

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

[0068] By controlling the left control part and the right control part, the output ends of the left connection part and the right control part are extended respectively, gradually close to the axial connection hole on the left and the lateral connection hole on the right, and the hydrogen content filled in the two groups of airbag groups is finely adjusted to make the axial connection hole and the lateral connection hole respectively consistent in height with the left connection part and the right connection part, and the left connection part and the right connection part are extended again until they are fixedly connected with the compaction fracture mold test part;

[0069] S9.2.2. Remove the cavity connection plate, expose the prefabricated seam and conduct the test:

[0070] Remove the cavity connection plates connecting the front floating cavity and the rear floating cavity and located on the left and right sides thereof. On the premise that the combination block and the carrier box are disconnected, hook the hook holes provided on the positioning blocks provided on both sides by hooking the clamps, and remove the first seam-making plate and the second seam-making plate respectively; open the left control part and the right control part, and push the left connection part and the right connection part at a certain rate; record the data measured by the stress and displacement sensors inside the left connection part and the right connection part;

[0071] S9.2.3. Until the gravel-mixed clay sample undergoes shear fracture and the data is processed:

[0072] The stress and displacement are recorded until the gravel-mixed clay soil sample undergoes shear fracture. The stress and displacement data are then processed to obtain the stress F (shear) and displacement L (shear) of the gravel-mixed clay soil sample in the shear fracture test. The expressions are as follows:

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

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

[0075] Among them, F3 and F4 represent the stress data recorded at the left connection part and the right connection part respectively; L3 and L4 represent the displacement data recorded at the left connection part and the right connection part respectively;

[0076] According to the F (shear) and L (shear) values, the stress-strain curve of shear fracture of gravel-mixed clay soil sample was obtained; the characteristic parameters of gravel-mixed clay in high core dam during shear fracture were analyzed through the shear fracture stress-strain curve, and the characteristic parameters included fracture toughness and fracture energy; thus, the shear fracture characteristics of gravel-mixed clay soil sample in high core dam were fully understood.

[0077] Preferably, the pulling rates of the front connecting part and the rear connecting part are set to multiple gears, so as to study the influence of different loading rates on the tensile fracture characteristics of gravel-mixed clay soil samples;

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

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

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

[0081] (2) The friction-free tensile-shear fracture test method for gravel-mixed clay in high core dams provided by the present invention uses the buoyancy principle to separate the compacted fracture mold test part from the working platform, float it on the water surface, and fix it through a connecting part, fundamentally solving the friction between the mold and the platform, greatly enriching the test methods for the fracture characteristics of gravel-mixed clay;

[0082] (3) The friction-free tensile-shear fracture test method for gravel-mixed clay in high core dams provided by the present invention can apply pulling and pushing forces to the compacted fracture mold test part while fixing the compacted fracture mold test part through the pushers on both sides and the front and rear pullers. At the same time, the force loading rate 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0084] Figure 2 It is a schematic diagram of the overall structure of the compaction and fracture mold in the present invention.

[0085] Figure 3 It is a schematic structural diagram of the test bearing part (with the cavity connecting plate omitted) in the present invention.

[0086] Figure 4 For the present invention Figure 3 Exploded view of the structure shown.

[0087] Figure 5 This is a diagram showing the distribution structure of the airbag group in the present invention and the changes during its inflation process.

[0088] Figure 6 It is a schematic diagram of the structure of the gravel-mixed clay soil sample in the present invention.

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

[0090] Figure 8 It is a schematic diagram of the test process of the friction-free high core dam gravel-mixed clay tensile-shear fracture test device of the present invention.

[0091] In the figure:

[0092] 1. Compact and fracture the mold;

[0093] 1-1, front half of the mold; 1-2, back half of the mold;

[0094] 1-1-1, first seam-making plate; 1-1-2, second seam-making 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 bottom plate; 1-1-8, axial connecting hole; 1-1-9, first threaded hole; 1-2-0, lateral connecting hole;

[0095] 1-3, front floating cavity; 1-4, rear floating cavity;

[0096] 1-3-1, second threaded hole; 1-3-2, horizontal bubble; 1-3-3, raised portion; 1-3-4, airbag assembly;

[0097] 1-5, cavity connecting plate; 1-6, rectangular ring wall;

[0098] 1-7, Z-shaped compacting plate; 1-7-1, gap in the middle of the compacting plate; 1-7-2, handle at the end of the compacting plate;

[0099] 2. Gravel-mixed clay soil sample; 2-1. Fracture section of soil sample; 2-2. Front end of soil sample; 2-3. Back end of soil sample;

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

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

[0102] 5. Front retractor; 5-1. Front connection part; 5-2. Front control part;

[0103] 6. Rear retractor; 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 DESCRIPTION

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

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

[0107] like Figure 1-7 As shown, the tensile-shear fracture test device for gravel-mixed clay in a high core wall dam without friction influence comprises a compaction fracture mold 1 and a hollow test trough 7, wherein the compaction fracture mold 1 is used to make gravel-mixed clay soil sample 2, and comprises a test bearing part, a rectangular annular 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 gravel-mixed clay soil sample 2, and can also be used to perform tensile fracture and shear fracture tests on the gravel-mixed clay soil 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 disassembled after the rectangular annular wall 1-6 and the Z-shaped compaction plate 1-7 are prepared. A rectangular groove is provided at the center of the top of the hollow test trough 7. The hollow test trough 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 can float the test bearing part loaded with the gravel-mixed clay soil sample 2;

[0108] The prepared gravel-mixed clay soil sample 2 has a soil sample fracture section 2-1, and the two sides thereof are respectively set as the soil sample front end 2-2 and the soil sample rear end 2-3. The gravel-mixed clay soil sample 2 prepared by the present invention is a central symmetrical structure, which is consistent with the cross-sectional shape of the Z-shaped compaction plate 1-7, and the size is adapted to the inner cavity of the test bearing part. The soil sample fracture section 2-1 is the position where the crack is generated during the actual tensile fracture or shear fracture;

[0109] The test bearing part 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, wherein 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, and the front floating cavity 1-3 and the rear floating cavity 1-4 are detachably connected through 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 half and the rear half of the mold, respectively, and are correspondingly arranged at the front end and the rear end of the gravel-mixed clay soil sample 2, and can respectively realize axial pulling and lateral pushing of the front end 2-2 and the rear end 2-3; During the process of preparing the gravel-mixed clay soil sample 2 and transferring it 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 firm integral plate structure; before the test, the cavity connecting plate 1-5 is removed, so that the front floating cavity 1-3 and the rear floating cavity 1-4 can 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 can stably float on the water;

[0110] The test bearing part cooperates with the rectangular ring wall 1-6 and the Z-shaped compaction plate 1-7 to compact the gravel-mixed clay material of the core wall of the high core wall dam to form the gravel-mixed clay soil sample 2. After the sample preparation is completed, 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 part;

[0111] The test bearing part is made of aluminum alloy, which has the advantages of high strength and low density, and can reduce the influence of deadweight on the test as much as possible. It is convenient to measure the fracture characteristics of gravel-mixed clay during the stretching or shearing process of gravel-mixed clay sample 2.

[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 front floating cavity 1-3 and the rear floating cavity 1-4 are open at the bottom and are embedded with an air bag group 1-3-4 for adjusting the buoyancy of the front floating cavity 1-3 and the rear floating cavity 1-4 and their floating angles on the water surface. The front half 1-1 of the mold and the front floating cavity 1-3 are both provided with a horizontal bubble 1-3-2 for detecting Measure the horizontality of the test bearing part loaded with the gravel-mixed clay soil sample 2; in this embodiment, the number of the horizontal 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 bubbles 1-3-2 is observed to determine whether the test bearing part loaded with the gravel-mixed clay soil sample 2 is horizontal. When the horizontality is poor, the buoyancy and initial angle of the test bearing part loaded with the gravel-mixed clay soil sample 2 are adjusted by inflating the airbag group as a whole or partially;

[0113] The left and right sides of the hollow test tank 7 are respectively provided with a left propeller 3 and a right propeller 4 which are symmetrically distributed in the center. The left propeller 3 and the right propeller 4 respectively push the front half 1-1 of the mold and the rear half 1-2 of the mold toward the center of the test device, so as to apply shear force to the gravel-mixed clay soil sample 2; the front and rear sides of the hollow test tank 7 are respectively provided with a front puller 5 and a rear puller 6 which are axially symmetrically distributed. The front puller 5 and the rear puller 6 respectively pull the front half 1-1 of the mold and the rear half 1-2 of the mold toward the front and rear sides of the test device, so as to apply tensile force to the gravel-mixed clay soil sample 2.

[0114] Further, in the above technical solution, the front half 1-1 of the mold and the rear half 1-2 of the mold both include a carrying box composed of a lateral push plate 1-1-5, an axial pull plate 1-1-6 and a fixed bottom plate 1-1-7, and 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 bottom plate 1-1-7, and the middle parts of the lateral push plate 1-1-5 and the axial pull plate 1-1-6 are respectively provided with lateral connecting holes 1-2-0 and axial connecting holes 1-1-8, and the fixed bottom plate 1-1-7 is provided with a first seam-making plate 1-1-1 and a second seam-making plate 1-1-2 which are axially symmetrically distributed at both ends of a side away from the axial pull plate 1-1-6, which are used for pre-fabricating seams on the left and right sides of the soil sample, and the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2 are both detachably mounted on the fixed bottom plate 1-1-7;

[0115] Recesses are provided at both ends of one side of the fixed base plate 1-1-7, and the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2 are respectively embedded in the recesses on both sides, and the thickness of the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2 coincide with the depth of the recesses. A gap is reserved between the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2 on the same fixed base plate 1-1-7, and the corresponding two groups of first seam-making plates 1-1-1 and second seam-making 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-making plate 1-1-1 and the second seam-making plate 1-1-2 is 0.3 mm, that is, when the two corresponding groups of first seam-making plates 1-1-1 and second seam-making plates 1-1-2 on the front and rear fixed base plates 1-1-7 are attached to each other, the thickness of the prefabricated seams is 0.6 mm.

[0117] Furthermore, in the above technical solution, the Z-shaped pressing plate 1-7 is made of aluminum alloy, and a press plate gap 1-7-1 is provided on both sides thereof, and the press plate gap 1-7-1 is adapted to the shape of the two groups of first seam-making plates 1-1-1 and second seam-making plates 1-1-2 corresponding to the front and rear fixed bottom plates 1-1-7 after being bonded to each other;

[0118] The Z-shaped compacting plate 1-7 is adapted to the shapes of the front half 1-1 of the mold and the rear half 1-2 of the mold so that it can be just inserted into the front half 1-1 of the mold and the rear half 1-2 of the mold;

[0119] A pressing plate end handle 1-7-2 is provided on the top of the Z-shaped pressing plate 1-7, so as to facilitate the removal of the Z-shaped pressing plate 1-7 after the gravel-mixed clay soil sample 2 is compacted.

[0120] Furthermore, in the above technical solution, the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2 are both provided with positioning blocks 1-1-3 and combination blocks 1-1-4, wherein the combination blocks 1-1-4 are located on the lower side of the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2, and are connected and combined with the fixed bottom plate 1-1-7 by bolts; the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2 are selected to be removed according to the progress of the test. When making gravel-mixed clay soil sample 2 and conducting tensile fracture test, it is not necessary to remove the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2, and when conducting shear fracture test, it is necessary to remove the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2.

[0121] The positioning block 1-1-3 is located in the middle of the side of the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2, and has a hook hole on its surface; when the shear fracture test is carried out, the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2 need to be removed, and the combination block 1-1-4 is disconnected from the bearing box, and is used to act as a pulling point in the lateral direction to be pulled out from the gravel-mixed clay soil sample 2. The hook hole set on the positioning block 1-1-3 can be hooked by a hook clamp, and it can be pulled out.

[0122] The rectangular ring wall 1-6 adopts a rectangular annular aluminum alloy ring body, and positioning grooves are opened on the bottom of both sides, and the positioning grooves match the structure of the two groups of first seam-making plates 1-1-1 and second seam-making plates 1-1-2 corresponding to the front and rear fixed bottom plates 1-1-7. The inside of the rectangular ring wall 1-6 fits with the outside of the test bearing part, and after being sleeved on the outside of the test bearing part, its top is flush with the test bearing part.

[0123] Further, in the above technical solution, first threaded holes 1-1-9 are provided on the three side surfaces of the fixed bottom plate 1-1-7, and raised portions 1-3-3 matching the three groups of first threaded holes 1-1-9 are provided on the tops of the front floating cavity 1-3 and the rear floating cavity 1-4, the carrying box is clamped on the inner sides of the three groups of raised portions 1-3-3, and is fixedly connected with the front floating cavity 1-3 or the rear floating cavity 1-4 by bolts, and the bolts penetrate the raised portions 1-3-3 and are screwed into the first threaded holes 1-1-9;

[0124] Second threaded holes 1-3-1 are provided at both ends of the opposite sides of the front floating cavity 1-3 and the rear floating cavity 1-4. The front floating cavity 1-3 and the rear floating cavity 1-4 are fixedly connected by a cavity connecting plate 1-5 and bolts. The cavity connecting plate 1-5 is an aluminum alloy connecting plate with holes. 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 second threaded holes 1-3-1.

[0125] Furthermore, in the above technical solution, the airbag group 1-3-4 includes a plurality of airbags distributed in a rectangular array, made of rubber material, and filled with hydrogen to ensure that the front floating cavity 1-3 and the rear floating cavity 1-4 float on the water surface;

[0126] A diaphragm is arranged between the multiple airbags, and a channel is arranged on the diaphragm, and a solenoid valve is embedded in the channel. Each airbag is provided with an independent inflation and deflation hole, so that the multiple airbags can be inflated and deflated synchronously or the gas volume in the airbags in a local area can be adjusted, such as Figure 5 As shown in (a), when not inflated, the lower surfaces of the multiple airbags are flush with the lower edges of the front floating cavity 1-3 and the rear floating cavity 1-4; Figure 5 As shown in (b), when inflated, the surface of the airbag will bulge; Figure 5 As shown in (c), in addition to uniform inflation, the gas in a single air bag in the air bag 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 penetrating the groove, and the water inlet hole 7-1 and the water outlet hole 7-2 are respectively used to replenish and replace the water in the groove.

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

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

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

[0131] The front retractor 5 includes a front connecting portion 5-1 and a front controlling portion 5-2 for connecting and controlling the extension and retraction of the output end of the front connecting portion 5-1;

[0132] The rear retractor 6 includes a rear connecting portion 6-1 and a rear controlling portion 6-2 for connecting and controlling the extension and retraction of the output end of the rear connecting portion 6-1;

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

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

[0135] Based on the above structure, the heights of the left connecting part 3-1 and the right connecting part 4-1 as well as the front connecting part 5-1 and the rear connecting part 6-1 can be controlled to facilitate docking between devices; and pushing or pulling force can be applied to the two carrying 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 driving mechanisms, which use at least one of a cylinder, an electric push rod, a hydraulic cylinder and a linear module.

[0137] Furthermore, in the above technical solution, the connection ends of the left connection part 3-1, the right connection part 4-1, the front connection part 5-1 and the rear connection part 6-1 are all provided with displacement sensors and stress sensors, which are respectively used to sense the displacement and stress value of the left connection part 3-1, the right connection part 4-1, the front connection part 5-1 and the rear connection part 6-1 during telescopic operation. Specifically, the collected data include the displacement from left to right and the thrust received by the left connection part 3-1, and the displacement from right to left and the thrust received by the right connection part 4-1 when the gravel-mixed clay soil sample 2 is sheared and broken; and the displacement from back to front and the tension received by the front connection part 5-1, and the displacement from front to back and the tension received by the rear connection part 6-1 when the gravel-mixed clay soil sample 2 is stretched and broken.

[0138] The friction-free high core dam gravel-mixed clay tensile-shear fracture test device provided by the present invention is used in accordance with Figure 8 As shown, where:

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

[0140] Figure 8 (b) shows the Figure 8 (a), the state of assembling the compaction fracture mold 1;

[0141] Figure 8 (c) shows the Figure 8 (b), preparing and compacting gravel-mixed clay soil sample 2;

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

[0143] Figure 8 (e) shows the Figure 8 (d) Based on the state where the Z-shaped compacting plate 1-7 and the rectangular ring wall 1-6 are removed;

[0144] Figure 8 (f) shows the Figure 8 (e) Based on the above, the test load-bearing part (compression fracture mold test part) is suspended;

[0145] Figure 8 (g) shows the Figure 8 (f) Based on the state of the fixed test load-bearing part (compression fracture mold test part);

[0146] Figure 8 (h) shows the Figure 8(g) Based on the above, the cavity connecting plates 1-5 are removed and tested;

[0147] Figure 8 (i) shows Figure 8 (h) until the gravel-mixed clay sample 2 undergoes tensile fracture;

[0148] Figure 8 (j) shows the Figure 8 (f) Based on the state of the fixed test load-bearing part (compression fracture mold test part);

[0149] Figure 8 (k) shows the Figure 8 (j) Based on the above, the cavity connecting plates 1-5 are removed and tested;

[0150] Figure 8 (l) shows the Figure 8 (k) until the gravel-mixed clay sample 2 undergoes shear fracture.

[0151] The present invention provides the following embodiments:

[0152] The tensile-shear fracture test method of gravel-mixed clay in high core dam without friction effect is adopted, and the specific steps are as follows:

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

[0154] Specifically, before conducting the fracture test, it is necessary to determine the optimal moisture content and maximum dry density of gravel-mixed clay in the material yard near the dam site of the high core dam at different gravel content. Referring to the specification, a heavy-duty compactor was selected to carry out the compaction test of gravel-mixed clay. The compaction hammer mass was 4.5kg, the hammer bottom diameter was 51mm, and the drop height was 457mm. The optimal moisture content and maximum dry density of gravel-mixed clay in the dam site of the high core dam at 30% to 50% gravel content. As shown in Table 1:

[0155] Table 1 Optimal moisture content and maximum dry density of gravel-mixed clay at 30% to 50% gravel content

[0156]

[0157] S2. Design test conditions:

[0158] When studying the effect of moisture content on fracture characteristics, five levels of 10.34%, 9.87%, 9.43%, 9.08%, and 8.72% were proposed for testing; when studying the effect of dry density on fracture characteristics, 2.16 g / cm 3 , 2.14g / cm 3 , 2.11g / cm 3 , 2.07g / cm3 , 2.03g / cm 3 Five levels were tested; when studying the effect of gravel content on fracture characteristics, five levels of 30%, 35%, 40%, 45% and 50% were proposed for testing; at the same time, other variables were controlled unchanged to design the test conditions.

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

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

[0161] Specifically, the bolts are screwed into the combination block 1-1-4 and the fixed base plate 1-1-7 on the first seam-making plate 1-1-1 from left to right in sequence, so that the first seam-making plate 1-1-1 is relatively fixed on the supporting box; the bolts are screwed into the combination block 1-1-4 and the fixed base plate 1-1-7 on the second seam-making plate 1-1-2 from right to left in sequence, so that the second seam-making plate 1-1-2 is relatively fixed on the supporting box, and then the first seam-making plate 1-1-1, the second seam-making plate 1-1-2 and the supporting box are combined into the front half 1-1 of the mold.

[0162] S3.2, rear part of combined mold 1-2:

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

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

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

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

[0167] S4.2, connect the front floating cavity 1-3 and the rear floating cavity 1-4 and cover them with a rectangular ring wall 1-6;

[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 engine oil is applied to the inner side of the rectangular ring wall 1-6 to ensure sufficient lubrication when in contact with the compaction fracture mold test part, and then the rectangular ring wall 1-6 is nested on the outer side of the compaction fracture mold test part, so that the three are tightly combined into one, together forming a compaction fracture mold 1.

[0169] S5, such as Figure 8 As shown in (c), prepare and compact gravel-mixed clay soil sample 2, the specific operation is as follows:

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

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

[0172] S5.3. Add the compaction fracture mold test part N times. After adding the gravel-mixed clay each time, use the Z-shaped compaction plates 1-7 to compact the gravel-mixed clay.

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

[0174] Specifically, the compacted gravel-mixed clay soil sample 2 is placed together with the compaction fracture mold 1 into the hollow test tank 7 through a hanging rope. At this time, since there is no water in the hollow test tank 7, the compaction fracture mold 1 is in contact with the bottom of the hollow test tank 7.

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

[0176] Specifically, the Z-shaped compaction plate 1-7 above the gravel-mixed clay soil sample 2 and the rectangular annular wall 1-6 sleeved on the outside of the front half 1-1 of the mold and the rear half 1-2 of the mold are removed, but the cavity connecting plate 1-5 is still kept in a state of being connected to the front half 1-1 of the mold and the rear half 1-2 of the mold. At this time, the front half 1-1 of the mold 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 part is suspended, and the specific operation is as follows:

[0178] S8.1. Fill a certain amount of hydrogen into the two airbag groups 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 due to the protrusion of the airbag groups 1-3-4;

[0179] S8.2, open the water inlet hole 7-1, close the water outlet hole 7-2, fill the groove of the hollow test tank 7 with water, and compact the fracture mold test part to continue to float up as the water surface rises under the action of buoyancy;

[0180] S8.3. By changing the hydrogen content in the airbags at different positions in the front floating cavity 1-3 and the rear floating cavity 1-4, the floating condition of the test part of the compaction fracture mold is adjusted, and the compaction fracture mold 1 is leveled with the help of the four horizontal 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 compacted fracture mold test part and the mass Y of gravel-mixed clay soil sample 2, and obtain the total mass of the test body consisting of the compacted fracture mold test part and gravel-mixed clay soil sample 2 as A+Y;

[0183] S8.1.1. Substitute A+Y into the following expression and solve for the buoyancy F(buoyancy) corresponding to A+Y;

[0184] A+Y=F(float)=G(discharge)=ρ(water)gV(discharge)

[0185] Wherein, ρ(water) represents the density of the liquid filled in the hollow test tank 7, and g is the acceleration due to gravity, which is 9.8 m / s 2 , V(displacement) represents the volume of liquid displaced by the test subject, and G(displacement) represents the displacement of the test subject when it floats on the water surface against gravity;

[0186] The inference is:

[0187] V(row)=(A+Y) / ρ(water)g

[0188] S8.1.2. Substitute the volume V(displaced) of the liquid displaced by the test subject when it floats into the following formula to calculate the minimum mass M of hydrogen that needs to be filled into the test subject to overcome gravity and achieve floating;

[0189] M=ρ(gas)V(exhaust)

[0190] Among them, ρ(gas) represents the density of hydrogen, which is 0.089g / m 3 .

[0191] Further, in the above technical solution, the leveling method described in S8.3 is implemented based on the structure of the airbag group, which includes a plurality of airbags distributed in a rectangular array for filling with hydrogen;

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

[0193] The connection end of the solenoid valve is electrically connected to a remote control chip, and the number of a specific airbag is input through the remote control to increase or decrease the amount of hydrogen filled therein.

[0194] Furthermore, in the above technical solution, the following conditions are met when the two airbag groups 1-3-4 are inflated:

[0195] When the upper and lower positions of the test body on the water surface are finely adjusted, multiple solenoid valves are opened to allow multiple airbags to communicate with each other, and the hydrogen mass P in any airbag is increased, and the hydrogen in other airbags is supplemented accordingly, and the overall height of the test body on the water surface is adjusted up and down;

[0196] When the solenoid valve between one of the airbags and the adjacent airbag fails to open due to signal control or failure, resulting in a concave shape relative to the outside, the solenoid valve on the airbag is controlled to open, and the mass of hydrogen 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, the two airbag groups 1-3-4 each contain 32 airbags. When the compaction fracture mold 1 needs to be leveled, the mass of hydrogen in one airbag is increased by P, and the mass of hydrogen in each of the other airbags is reduced by P / 31;

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

[0198] At this point, the entire core wall gravel-mixed clay tensile-shear fracture test device has been assembled;

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

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

[0201] S9.1. Conduct tensile fracture test on core wall gravel-mixed clay:

[0202] 1. The tensile fracture test operation process of gravel-mixed clay sample 2 is as follows:

[0203] S9.1.1: Figure 8 (g) shows the fixed compression fracture mold test part:

[0204] By controlling the front control part 5-2 and the rear control part 6-2, the output ends of the front connection part 5-1 and the rear connection part 6-1 are extended respectively, gradually close to the front axial connection hole 1-1-8 and the rear lateral connection hole 1-2-0, and the hydrogen content filled in the two groups of airbag groups 1-3-4 is finely adjusted to make the axial connection hole 1-1-8 and the lateral connection hole 1-2-0 respectively consistent in height with the front connection part 5-1 and the rear connection part 6-1, and the front connection part 5-1 and the rear connection part 6-1 are extended again until they are fixedly connected with the compaction fracture mold test part;

[0205] S9.1.2 If Figure 8 As shown in (h), remove the cavity connecting plate 1-5 and conduct the test:

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

[0207] S9.1.3: Figure 8 (i) until the gravel-mixed clay sample 2 undergoes tensile fracture and the data is processed:

[0208] The stress and displacement are recorded until the gravel-mixed clay sample 2 undergoes tensile fracture. The stress and displacement data are then processed to obtain the stress F (tensile) and displacement L (tensile) of the gravel-mixed clay sample 2 in the tensile fracture test. The expressions are as follows:

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

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

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

[0212] According to the F (tensile) and L (tensile) values, the stress-strain curve of the tensile fracture of gravel-mixed clay sample 2 was obtained; the characteristic parameters of the high core wall dam gravel-mixed clay in the tensile fracture process were analyzed through the tensile fracture stress-strain curve, and the characteristic parameters included fracture toughness and fracture energy; thus, the tensile fracture characteristics of the high core wall dam gravel-mixed clay sample 2 were fully understood.

[0213] Furthermore, in the above technical solution, the pulling rate of the front connecting part 5-1 and the rear connecting part 6-1 is set to multiple gears, which is used to study the influence of different loading rates on the tensile fracture characteristics of the gravel-mixed clay soil sample 2; for example, the multiple gears are set to gear 1 (0.005mm / s), gear 2 (0.01mm / s), gear 3 (0.02mm / s), gear 4 (0.05mm / s), and gear 5 (0.1mm / s), respectively, which can simulate the stress conditions of the gravel-mixed clay at different heights of the core wall of the high core wall dam during the construction period and the operation period when the core wall is unevenly settled. Since the core wall dam is high, the uneven settlement of the gravel-mixed clay in the middle and low parts of the core wall is small, and the test can be carried out at gear 1 or 2; the uneven settlement of the gravel-mixed clay in the middle and high parts of the core wall is large, and the test can be carried out at gear 4 or 5.

[0214] It should be noted that when the front connecting portion 5-1 and the rear connecting portion 6-1 are respectively at level 1 (0.005 mm / s), since the front and rear are pulled simultaneously, the loading rate for the effect on the tensile fracture characteristics of gravel-mixed clay studied is 0.01 mm / s. The same is true for other levels.

[0215] S9.2. Carry out shear fracture test on core wall with gravel-mixed clay:

[0216] 2. The shear fracture test operation process for gravel-mixed clay sample 2 is as follows:

[0217] S9.2.1. Figure 8 (j) shows the fixed compaction fracture mold test part:

[0218] By controlling the left control part 3-2 and the right control part 4-2, the output ends of the left connection part 3-1 and the right control part 4-2 are extended respectively, gradually close to the axial connection hole 1-1-8 on the left and the lateral connection hole 1-2-0 on the right, and the hydrogen content filled in the two groups of airbag groups 1-3-4 is finely adjusted to make the axial connection hole 1-1-8 and the lateral connection hole 1-2-0 respectively consistent in height with the left connection part 3-1 and the right connection part 4-1, and the left connection part 3-1 and the right connection part 4-1 are extended again until they are fixedly connected with the compaction fracture mold test part;

[0219] S9.2.2 If Figure 8 As shown in (k), the cavity connecting plates 1-5 are removed to expose the prefabricated seams and conduct the test:

[0220] Remove the cavity connection plates 1-5 connecting the front floating cavity 1-3 and the rear floating cavity 1-4 and located on the left and right sides thereof. On the premise that the combination block 1-1-4 is disconnected from the carrier box, hook the hook holes provided on the positioning blocks 1-1-3 provided on both sides by hooking the clamps, and remove the first seam-making plate 1-1-1 and the second seam-making plate 1-1-2 respectively; open the left control unit 3-2 and the right control unit 4-2, and push the left connection unit 3-1 and the right connection unit 4-1 at a certain rate; record the data measured by the stress and displacement sensors inside the left connection unit 3-1 and the right connection unit 4-1;

[0221] S9.2.3: Figure 8 As shown in (l), until the gravel-mixed clay sample 2 undergoes shear fracture and the data is processed:

[0222] The stress and displacement are recorded until the gravel-mixed clay sample 2 undergoes shear fracture. The stress and displacement data are then processed to obtain the stress F (shear) and displacement L (shear) of the gravel-mixed clay sample 2 in the shear fracture test. The expressions are as follows:

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

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

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

[0226] According to the F (shear) and L (shear) values, the stress-strain curve of shear fracture of gravel-mixed clay sample 2 was obtained. The characteristic parameters of gravel-mixed clay in the high core dam during shear fracture were analyzed through the shear fracture stress-strain curve, and the characteristic parameters included fracture toughness and fracture energy. Thus, the shear fracture characteristics of gravel-mixed clay sample 2 in the high core dam were fully understood.

[0227] Furthermore, in the above technical solution, the speed of the left connecting part 3-1 and the right connecting part 4-1 is set to multiple gears, which is used to study the influence of different loading rates on the shear fracture characteristics of the gravel-mixed clay soil sample 2. For example, the multiple gears are set to gear 1 (0.005mm / s), gear 2 (0.01mm / s), gear 3 (0.02mm / s), gear 4 (0.05mm / s), and gear 5 (0.1mm / s), respectively, which can simulate the stress conditions of the gravel-mixed clay at different heights of the core wall of the high core wall dam during the construction period and the operation period. Since the core wall dam is high, the uneven settlement of the gravel-mixed clay in the middle and low parts of the core wall is small, and the test can be carried out at gear 1 or 2; the uneven settlement of the gravel-mixed clay in the middle and high parts of the core wall is large, and the test can be carried out at gear 4 or 5.

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

[0229] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within 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 belong to the protection scope of the present invention.

Claims

1. A tensile-shear fracture test method for gravel-mixed clay in high core dams without friction, characterized by: The steps include: S1. Collect soil samples and determine their optimal moisture content and maximum dry density at different gravel content; S2. Design and test 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 parts. Adjust each 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 parts. Adjust each 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 water content and divide them into multiple parts. Adjust each soil sample to different gravel content levels to study the effect of gravel content on fracture characteristics; S3, combined mold front half (1-1) and mold back half (1-2): In the same steps, bolts are used to screw into the assembly blocks (1-1-4) and the fixing bottom plate (1-1-7) on the first seam-making plate (1-1-1) and the second seam-making plate (1-1-2) in sequence, and the first seam-making plate (1-1-1) and the second seam-making plate (1-1-2) are relatively fixed on the carrying box, so that the two sets of the first seam-making plate (1-1-1), the second seam-making plate (1-1-2) and the carrying box together form a front half (1-1) and a rear half (1-2) of the mold with the same structure; S4. Assembling the compaction fracture mold (1): The front half (1-1) and the rear half (1-2) of the mold are placed symmetrically in the center, and three groups of protrusions (1-3-3) are fixedly connected to the corresponding first threaded holes (1-1-9) using bolts, and are respectively installed on the front floating cavity (1-3) and the rear floating cavity (1-4), and the front floating cavity (1-3) and the rear floating cavity (1-4) are fixedly connected using a cavity connecting plate (1-5) to form a compaction fracture mold test part, and a rectangular ring wall (1-6) is sleeved on the outer side thereof to assemble into a compaction fracture mold (1); S5. Preparation and compaction of gravel-mixed clay soil sample (2): The gravel-mixed clay soil sample prepared in S2 is added into the compaction fracture mold (1) assembled in S4, and compacted using a Z-shaped compaction plate (1-7) to obtain a gravel-mixed clay soil sample (2); S6, transferring the compacted fracture mold to the hollow test tank (7); S7, removing the Z-shaped compacting plate (1-7) and the rectangular ring wall (1-6), while still keeping the cavity connecting plate (1-5) in a state of being connected to the front half of the mold (1-1) and the rear half of the mold (1-2); S8, suspending the compacted fracture mold test part until its bottom is separated from the bottom wall of the hollow test tank (7) and is in a friction-free state, the process is as follows: S8.

1. Fill the two airbag groups (1-3-4) at the bottom of the front floating cavity (1-3) and the rear floating cavity (1-4) with hydrogen to lift the front floating cavity (1-3) and the rear floating cavity (1-4); S8.2, opening the water inlet hole (7-1) and closing the water outlet hole (7-2), filling the groove of the hollow test tank (7) with water, so that the compacted fracture mold test part continues to float up as the water surface rises under the action of buoyancy; S8.3, by changing the hydrogen content in the airbags at different positions on the two airbag groups (1-3-4), the compaction fracture mold test part is leveled; S9. After the test apparatus is assembled, the test is performed, including the tensile fracture test S9.1 and the shear fracture test S9.2; S9.

1. Conduct tensile fracture test on core wall gravel-mixed clay: The compaction fracture mold test part is fixed, the cavity connection plate (1-5) is removed, and the front puller (5) and the rear puller (6) are used to pull the front half (1-1) and the rear half (1-2) of the mold to the two sides respectively, and the measurement data of the stress and displacement sensors at the connection ends are recorded. When the gravel-mixed clay soil sample (2) undergoes tensile fracture, the stress-strain curve of the tensile fracture of the gravel-mixed clay soil sample (2) is obtained, and the tensile fracture characteristics of the gravel-mixed clay soil sample (2) of the high core wall dam are analyzed; S9.

2. Carry out shear fracture test on core wall with gravel-mixed clay: The compaction fracture mold test part is fixed, the cavity connection 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) respectively push the front half (1-1) and the rear half (1-2) of the mold toward the center of the test device, and the measurement data of the stress and displacement sensors at the connection ends are recorded. When the gravel-mixed clay sample (2) undergoes shear fracture, the test is stopped, and the stress-strain curve of the shear fracture of the gravel-mixed clay sample (2) is obtained, and the shear fracture characteristics of the gravel-mixed clay sample (2) of the high core wall dam are analyzed.

2. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect according to claim 1, characterized in that: In S1, the soil sample used was gravel-mixed clay from the material yard near the dam site of the high core dam. A heavy-duty compactor was selected to carry out compaction tests on the gravel-mixed clay to obtain the optimal moisture content and maximum dry density of the gravel-mixed clay soil sample at a gravel content of 30% to 50%.

3. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect according to claim 1, characterized in that: In S2, A) when designing the test conditions, the proposed range of soil sample moisture content is set to 8.72% to 10.34% while keeping other variables unchanged; B) When designing the test conditions, the proposed range of soil sample dry density is set to 2.03 g / cm2 while keeping other variables unchanged. 3 ~16g / cm 3 ; C) When designing the test conditions, the proposed range of the gravel content of soil samples is set to 30% to 50% while keeping other variables unchanged.

4. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect according to claim 1, characterized in that: When processing the gravel-mixed clay soil sample (2) in S5, the specific operation steps are as follows: S5.

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

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

3. Add the gravel-mixed clay prepared in S5.2 into the compaction fracture mold test part N times. After each addition of the gravel-mixed clay, use a Z-shaped compaction plate (1-7) to compact the gravel-mixed clay immediately.

5. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect according to claim 1, characterized in that: The hydrogen filling amount of the two airbag groups (1-3-4) in S8.1 is calculated by the following steps: S8.1.

1. Collect the mass A of the compacted 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 consisting of the compacted fracture mold test part and the gravel-mixed clay soil sample (2) as A+Y; S8.1.

1. Substitute A+Y into the following expression and solve for the buoyancy F(buoyancy) corresponding to A+Y; A+Y=F(float)=G(discharge)=ρ(water)gV(discharge) Wherein, ρ(water) represents the density of the liquid filled in the hollow test tank (7), and g is the acceleration due to gravity, which is 9.8 m / s 2 , V(displacement) represents the volume of liquid displaced by the test subject, and G(displacement) represents the displacement of the test subject when it floats on the water surface against gravity; The inference is: V(row)=(A+Y) / ρ(water)g S8.1.

2. Substitute the volume V(displaced) of the liquid displaced by the test subject when it floats into the following formula to calculate the minimum mass M of hydrogen that needs to be filled into the test subject to overcome gravity and achieve floating; M=ρ(gas)V(exhaust) Among them, ρ(gas) represents the density of hydrogen, which is 0.089g / m 3 .

6. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect according to claim 1, characterized in that: The leveling method in S8.3 is implemented based on the structure of the airbag group (1-3-4), which includes a plurality of airbags distributed in a rectangular array for filling with hydrogen; A diaphragm is arranged between the multiple airbags, and a channel is arranged on the diaphragm, and a solenoid valve is embedded in the channel. Each airbag is provided with an independent inflation and deflation hole, so that the multiple airbags can be inflated and deflated synchronously or the gas volume in the airbags in a local area can be adjusted; The connection end of the solenoid valve is electrically connected to a remote control chip, and the number of a specific airbag is input through the remote control to increase or decrease the amount of hydrogen filled therein.

7. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect according to claim 6, characterized in that: When the two airbag groups (1-3-4) are inflated, the following conditions exist: When the upper and lower positions of the test body on the water surface are finely adjusted, multiple solenoid valves are opened to allow multiple airbags to communicate with each other, and the hydrogen mass P in any airbag is increased, and the hydrogen in other airbags is supplemented accordingly, and the overall height of the test body on the water surface is adjusted up and down; When the solenoid valve between one of the airbags and the adjacent airbag fails to open due to signal control or failure, causing it to be concave relative to the outside, the solenoid valve on this airbag is controlled to open, and the mass of hydrogen in each of the other airbags is correspondingly reduced by P / (n-1), where n is the number of airbags in each airbag group (1-3-4); 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 area on the lower side of the compaction fracture mold (1) is increased, and the increased hydrogen mass P is filled into the corresponding airbag from the external gas transmission pipe.

8. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect according to claim 1, characterized in that: In S9.1, the tensile fracture test procedure for gravel-mixed clay sample (2) is as follows: S9.1.

1. Fixed Compaction Fracture Die Test Section: By controlling the front control part (5-2) and the rear control part (6-2), the output ends of the front connection part (5-1) and the rear connection part (6-1) are extended respectively, gradually approaching the front axial connection hole (1-1-8) and the rear lateral connection hole (1-2-0), and the hydrogen content filled in the two airbag groups (1-3-4) is finely adjusted, so that the axial connection hole (1-1-8) and the lateral connection hole (1-2-0) are respectively in the same height with the front connection part (5-1) and the rear connection part (6-1), and the front connection part (5-1) and the rear connection part (6-1) are extended again until they are fixedly connected with the compaction fracture mold test part; S9.1.

2. Remove the cavity connection plate (1-5) and conduct the test: The cavity connection plates (1-5) connecting the front floating cavity (1-3) and the rear floating cavity (1-4) and located on the left and right sides are removed, and the front control part (5-2) and the rear control part (6-2) are turned on, and the front connection part (5-1) and the rear connection part (6-1) are pulled at a certain rate; and the data measured by the stress and displacement sensors connected to the front connection part (5-1) and the rear connection part (6-1) are recorded; S9.1.

3. Until the gravel-mixed clay sample (2) undergoes tensile fracture and the data is processed: The stress and displacement are recorded until the gravel-mixed clay soil sample (2) undergoes tensile fracture. The stress and displacement data are then processed to obtain the stress F (tensile) and displacement L (tensile) experienced by the gravel-mixed clay soil sample (2) in the tensile fracture test. The expressions are as follows: F(pull)=(|F5|+|F6|) / 2 L(pull)=(|L5|+|L6|) / 2 Wherein, F5 and F6 represent stress data recorded by the front connecting portion (5-1) and the rear connecting portion (6-1), respectively; L5 and L6 represent displacement data recorded by the front connecting portion (5-1) and the rear connecting portion (6-1), respectively; According to the F (tensile) and L (tensile) values, the stress-strain curve of the tensile fracture of the gravel-mixed clay sample (2) is obtained; the characteristic parameters of the high core dam gravel-mixed clay in the tensile fracture process are analyzed through the tensile fracture stress-strain curve, and the characteristic parameters include fracture toughness and fracture energy; thus, the tensile fracture characteristics of the high core dam gravel-mixed clay sample (2) are fully understood.

9. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect according to claim 1, characterized in that: In S9.2, the shear fracture test procedure for gravel-mixed clay sample (2) is as follows: S9.2.

1. Fixed Compaction Fracture Die Test Section: By controlling the left control part (3-2) and the right control part (4-2), the output ends of the left connection part (3-1) and the right control part (4-2) are extended respectively, gradually close to the axial connection hole (1-1-8) on the left and the lateral connection hole (1-2-0) on the right, and the hydrogen content filled in the two groups of airbag groups (1-3-4) is finely adjusted, so that the axial connection hole (1-1-8) and the lateral connection hole (1-2-0) are respectively consistent in height with the left connection part (3-1) and the right connection part (4-1), and the left connection part (3-1) and the right connection part (4-1) are extended again until they are fixedly connected with the compaction fracture mold test part; S9.2.

2. Remove the cavity connecting plate (1-5), expose the prefabricated seam and conduct the test: The cavity connection plates (1-5) connecting the front floating cavity (1-3) and the rear floating cavity (1-4) and located on the left and right sides thereof are removed, and on the premise that the combination block (1-1-4) is disconnected from the carrier box, the first seam-making plate (1-1-1) and the second seam-making plate (1-1-2) are removed respectively by hooking the hook holes provided on the positioning blocks (1-1-3) provided on both sides with hook clamps; the left control part (3-2) and the right control part (4-2) are opened, and the left connection part (3-1) and the right connection part (4-1) are pushed forward at a certain speed; and the data measured by the stress and displacement sensors inside the left connection part (3-1) and the right connection part (4-1) are recorded; S9.2.

3. Until the gravel-mixed clay sample (2) undergoes shear fracture and the data is processed: The stress and displacement are recorded until the gravel-mixed clay soil sample (2) undergoes shear fracture. The stress and displacement data are then processed to obtain the stress F (shear) and displacement L (shear) experienced by the gravel-mixed clay soil sample (2) in 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 by the left connecting part (3-1) and the right connecting part (4-1), respectively; L3 and L4 represent the displacement data recorded by the left connecting part (3-1) and the right connecting part (4-1), respectively; According to the F (shear) and L (shear) values, the stress-strain curve of the shear fracture of the gravel-mixed clay sample (2) is obtained; the characteristic parameters of the gravel-mixed clay in the high core dam during the shear fracture process are analyzed through the shear fracture stress-strain curve, and the characteristic parameters include fracture toughness and fracture energy; thus, the shear fracture characteristics of the gravel-mixed clay sample (2) of the high core dam are fully understood.

10. The tensile-shear fracture test method for gravel-mixed clay in high core dam without friction effect 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 gears for studying the influence of different loading rates on the tensile fracture characteristics of the gravel-mixed clay sample (2); The advancing speeds of the left connecting part (3-1) and the right connecting part (4-1) are set to multiple gears, which are used to study the influence of different loading rates on the shear fracture characteristics of the gravel-mixed clay sample (2).

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