Rock freezing and thawing experimental device and experimental method based on porosity and temperature difference change

Abstract

The invention provides a rock freezing and thawing experimental device and experimental method based on porosity and temperature difference change, and relates to the field of rock mass performance research, the rock freezing and thawing experimental device comprises an experimental box and a swing mechanism arranged below the experimental box, and the swing mechanism is used for driving the experimental box to rotate to simulate a slope angle; the experiment box comprises a first side wall and a second side wall which are concentrically arranged, the first side wall forms a containing cavity, a freezing and thawing cavity is formed between the first side wall and the second side wall, the freezing and thawing cavity is divided into a plurality of freezing and thawing chambers with independent temperature control by temperature isolation plates in the vertical direction, and the strain monitoring system is used for monitoring the strain of a sample in a height area corresponding to each freezing and thawing chamber; the water control system is used for controlling the height of the water surface in the freezing and thawing cavity, the freezing and thawing chambers with independent and controllable temperatures are arranged in the vertical direction to simulate the temperatures of the rock at different positions underground, and the rock is naturally dissolved through the water control system, so that the environment of the rock can be simulated more truly, and the simulated result is more accurate.

Description

Technical Field

[0001] The invention relates to the field of rock mass performance research, and in particular to a rock freeze-thaw experimental device and an experimental method based on porosity and temperature difference changes. Background Art

[0002] With the continuous investment in transportation construction in high-altitude areas, the stability of rock in cold regions is a very important research topic. Due to the high day and night temperatures in cold regions, the rock mass on the slope is in a freeze-thaw process all year round, and the rock mass will be at risk of cracking, sliding and collapse, which will cause great damage to the road rock. Therefore, in order to ensure the normal operation of road traffic and the safety of national property, the study of the stability of rock mass in cold regions has always been a hot topic in rock engineering.

[0003] However, the traditional freeze-thaw experiment simply places the specimen in a water environment and then repeatedly freezes and thaws it to conduct the experiment. In the actual freezing and thawing process of rocks in cold regions, the freezing temperatures of rocks at different depths are different. The deeper the rock, the higher the temperature. In addition, during the actual freezing and thawing process, the rock mass is not always in a water environment, but is only in a certain water content state. The experimental process cannot simulate the actual freezing and thawing conditions, resulting in large errors in the freeze-thaw experimental results. Summary of the invention

[0004] The present invention provides a rock freeze-thaw experimental device and an experimental method based on porosity and temperature difference changes, which aims to solve the problem that the existing freeze-thaw experiment cannot restore the real state of rock when it is frozen in the simulation experiment, and the results of the freeze-thaw experiment have large errors.

[0005] In order to achieve the above-mentioned purpose, an embodiment of the present invention provides a rock freeze-thaw experimental device based on porosity and temperature difference changes, comprising:

[0006] An experimental box and a swing mechanism disposed below the experimental box, wherein the swing mechanism is used to drive the experimental box to rotate to simulate a slope angle;

[0007] The experimental box comprises a first side wall and a second side wall arranged concentrically, the first side wall surrounds and forms a containing cavity for accommodating a sample, a freeze-thaw cavity is formed between the first side wall and the second side wall, the temperature isolation plate divides the freeze-thaw cavity into a plurality of freeze-thaw chambers in the vertical direction, and the temperature in each freeze-thaw chamber is independently controlled;

[0008] The strain monitoring system installed in the freeze-thaw chamber is used to monitor the strain of the sample in the corresponding height zone of each freeze-thaw chamber;

[0009] The water control system arranged in the freeze-thaw cavity is used to control the water level in the freeze-thaw cavity.

[0010] Preferably, each of the freeze-thaw chambers is provided with a temperature control unit and a temperature measuring unit.

[0011] Preferably, a plurality of longitudinally arranged support screws are provided in the inner ring of the freeze-thaw chamber, a pallet nut is screwed onto the support screw, and a plurality of the temperature isolation plates are overlapped on the pallet nut to adjust the height of each freeze-thaw chamber.

[0012] Preferably, the first side wall and the second side wall are made of transparent material.

[0013] Preferably, the swing mechanism comprises a base, a chassis and a lifting unit, the chassis is hinged to the base, and the lifting unit pushes the chassis to rotate around the hinge to change the angle between the chassis and the base.

[0014] Based on the same inventive concept, the present application also provides a rock freeze-thaw experimental method based on porosity and temperature difference changes, using the aforementioned experimental device, including:

[0015] S10. Obtain a rock core on a slope in a freeze-thaw zone as a sample, divide the sample into a plurality of height lines along the longitudinal direction, and obtain the temperature of each height line interval;

[0016] S20. Place the sample in the accommodating chamber, adjust each temperature baffle to correspond to the height line of the sample, and adjust the angle of the swing mechanism to simulate the slope;

[0017] S30. Inject water to a height of H into the freeze-thaw cavity to immerse the sample, and after the sample reaches a water saturated state, drain the water from the freeze-thaw cavity;

[0018] S40. Adjust the temperature of each freeze-thaw chamber, perform a freeze-thaw experiment on the sample for a cycle, inject water with a height of L into the freeze-thaw chamber during the thawing process to maintain a constant moisture content in the freeze-thaw chamber; obtain the deformation of the sample during the freezing and thawing process;

[0019] S50. Repeat steps S30-S40 to obtain deformation data of the sample after multiple freeze-thaw cycles.

[0020] Preferably, in step S10, a core is drilled downward perpendicularly to the surface of the slope.

[0021] Preferably, in step S40, the initial porosity and the increased porosity of the sample are obtained, and the water injection height L during the thawing process is obtained based on the initial porosity, the increased porosity and the water injection height H. The first water injection height L satisfies:

[0022]

[0023] Where A is the initial porosity of the sample, and B is the increased porosity of the sample.

[0024] Preferably, in step S10, a portion of the sample is cut as a basic sample, and the freeze-thaw temperature corresponding to the basic sample is obtained;

[0025] Obtain the weight m0 of the basic sample in a water-saturated state and the weight m1 after drying and calculate the initial porosity A of the basic sample;

[0026] A freeze-thaw experiment is performed on the basic sample at the freeze-thaw temperature corresponding to the basic sample to obtain the weight m2 of the basic sample in a water-saturated state and the weight m3 after drying, and the increased porosity B of the basic sample is calculated;

[0027] The initial porosity and increased porosity of the base sample are the same as the initial porosity and increased porosity of the sample.

[0028] The above scheme of the present invention has the following beneficial effects:

[0029] In this application, in order to more realistically restore the environment in which the rock is located, several freeze-thaw chambers with independently controllable temperatures are set up in the vertical direction to simulate the temperature of the rock at different locations underground, simulate the most realistic temperature conditions of the rock at different depths, and use a water control system to naturally dissolve the rock, so that the sample is closer to the water content under natural conditions. When performing freeze-thaw cycles, the environment of the rock can be simulated more realistically, and the simulated results are more accurate.

[0030] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is an overall schematic diagram of the present invention;

[0032] Figure 2 It is a schematic diagram of sample collection.

[0033] [Description of Reference Numerals]

[0034] 10-test box, 11-first side wall, 12-second side wall, 13-temperature isolation plate, 14-temperature control unit, 16-support screw, 17-water inlet pipe, 21-base, 22-chassis, 23-lifting unit, N-sample. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0036] like Figure 1As shown, an embodiment of the present invention provides a rock freeze-thaw experimental device based on porosity and temperature difference changes, including an experimental box 10 and a swing mechanism, wherein the experimental box 10 is arranged on the swing mechanism, and the swing mechanism drives the experimental box 10 to rotate to simulate different slope angles. Specifically, the experimental box 10 includes two concentrically arranged first side walls 11, a second side wall 12, and a top wall and a bottom wall arranged above and below the first side wall 11 and the second side wall 12, the diameter of the first side wall 11 is smaller than the diameter of the second side wall 12, the first side wall 11 and the second side wall 12 are arranged on the bottom wall, the area surrounded by the first side wall 11 is a receiving cavity, and the receiving cavity is used to accommodate the sample N, and a freeze-thaw cavity is formed around the first side wall 11 and the second side wall 12, and a plurality of temperature isolation plates 13 are arranged in the freeze-thaw cavity. It can be understood that the temperature isolation plate 13 is annular, and the plurality of temperature isolation plates 13 are arranged along the vertical direction of the experimental box 10, and the plurality of temperature isolation plates 13 divide the freeze-thaw cavity into a plurality of freeze-thaw chambers in the vertical direction, and the temperature in each freeze-thaw chamber is independently controlled. The temperature isolation plate 13 is made of heat insulating material to avoid heat exchange between adjacent freeze-thaw chambers.

[0037] A strain monitoring system is also provided in the freeze-thaw chamber, and the strain monitoring system includes a plurality of strain gauges, and the strain gauges are used to be attached to the sample N. The strain gauges are used to detect the strain of the sample N at the corresponding heights of different freeze-thaw chambers.

[0038] A water control system is also provided in the freeze-thaw cavity, and the water control system includes a water inlet pipe 17, a drainage pipe and a liquid level meter. The water inlet pipe 17 is provided above the accommodating cavity, and the drainage pipe is provided below the accommodating cavity. Preferably, an electromagnetic drainage valve is also provided on the drainage pipe. The liquid level meter is provided in the accommodating cavity to reflect the liquid level in the accommodating cavity. The water control system can add and discharge water into the freeze-thaw cavity to simulate different water volumes in the rock.

[0039] Furthermore, a temperature control unit 14 and a temperature measuring unit are respectively provided in each freeze-thaw chamber, wherein the temperature control unit 14 is used to adjust the temperature of each freeze-thaw chamber so that each freeze-thaw chamber can be at a different temperature, and the temperature measuring unit is used to feed back the temperature in the freeze-thaw chamber.

[0040] In this embodiment, the temperature of the freeze-thaw chamber is independent and controllable, which can better simulate the temperature gradient of the rock in the real environment, and help improve the accuracy of the experimental structure.

[0041] Furthermore, a plurality of longitudinally arranged support screws 16 are provided in a ring inside the freeze-thaw chamber, and each support screw 16 is threaded with at least one pallet nut, which can move along the axial direction of the support screw 16. The pallet nut is used to support the temperature isolation plate 13, thereby adjusting the distance between adjacent isolation plates to match the height line of the sample N.

[0042] The aforementioned swing mechanism also includes a base 21, a chassis 22 and a lifting unit 23, wherein the chassis 22 is used to fix the experimental box 1, one end of the chassis 22 is hinged to the base 21, and the other end of the chassis 22 is provided with a lifting unit 23. Driven by the lifting unit 23, the chassis 22 rotates relative to the base 21 at the junction of the chassis 22 and the base 21, thereby changing the angle between the chassis 22 and the base 21.

[0043] It can be clearly seen that the present application is also provided with a control system, which adjusts the temperature of each freeze-thaw chamber and obtains the strain of sample N.

[0044] Preferably, the first side wall 11 and the second side wall 12 are both made of transparent material to facilitate observation of the sample N.

[0045] Based on the same inventive concept, the present application also provides a rock freeze-thaw experimental method based on porosity and temperature difference changes, using the aforementioned experimental device and including the following steps:

[0046] S10. Obtain a rock core on the slope of the freeze-thaw zone as sample N, divide sample N into a plurality of height lines along the longitudinal direction, and obtain the temperature of each height line interval.

[0047] like Figure 2 , a hole is drilled on the surface perpendicular to the slope of the freeze-thaw zone to obtain the core below the surface as sample N. After taking out sample N, multiple height lines are divided in the longitudinal direction of sample N. The longitudinal direction of sample N refers to the direction of sample N vertical to the surface underground. Multiple adjacent height lines constitute a height line area, and the temperature of each height line interval in sample N is obtained.

[0048] When obtaining the temperature of the N height line interval of the sample, it can be obtained by measuring the temperature at the corresponding height of the drill hole. The temperature includes the freezing temperature and the thawing temperature, which is used for subsequent simulation of freezing and thawing.

[0049] S20. According to the height of the sample N, at least one strain gauge is affixed in each height line interval, the sample N with the strain gauge is placed in the accommodating cavity, and the temperature isolation plate 13 is adjusted so that the temperature isolation plate 13 is arranged one-to-one with the height line. Correspondingly, the height line interval corresponds to the freeze-thaw chamber, and each freeze-thaw chamber can provide different temperatures for the height line interval matching it.

[0050] After adjusting the position of the temperature isolation plate 13, the swing mechanism is adjusted to simulate the angle of the slope.

[0051] S30. Inject water to a height of H into the freeze-thaw cavity to immerse the sample N, and after the sample N reaches a water saturated state, drain the water from the freeze-thaw cavity;

[0052] S40. Adjust the temperature of each freeze-thaw chamber, perform a freeze-thaw experiment on sample N for one cycle, inject water of a height of L into the freeze-thaw chamber during the thawing process to maintain a constant moisture content in the freeze-thaw chamber; obtain the deformation of sample N during the freezing and thawing process;

[0053] Adjust the temperature of each freeze-thaw chamber. Specifically, first adjust the temperature of each freeze-thaw chamber to the freezing temperature corresponding to the sample N under the surface. After freezing, adjust the temperature of each freeze-thaw chamber to the thawing temperature corresponding to the sample N under the surface. During the thawing process, inject water with a height of L into the freeze-thaw cavity again through the water control system. The purpose of the secondary water injection is to maintain the water content in the freeze-thaw cavity constant. The strain gauge obtains the deformation data of the sample N in different height line intervals during the freezing and thawing process.

[0054] S50. Repeat the aforementioned steps S30-S40, perform multiple freeze-thaw cycles on the sample N, and obtain deformation data of each height line interval of the sample N after each freeze-thaw cycle.

[0055] In step S40, the first water injection height L satisfies:

[0056]

[0057] Where A is the initial porosity of sample N, and B is the increased porosity of sample N.

[0058] Since the porosity of sample N increases by the same amount after each freeze-thaw cycle, that is, the porosity increases by B each time, so during the Nth water injection, the water injection height

[0059] In order to obtain the initial porosity A and increased porosity B of sample N, in step S10, a portion of sample N is cut off as a sample base. Generally speaking, the sample base obtained is the upper end or end of sample N, which is convenient for obtaining the freezing and thawing temperatures corresponding to the sample base.

[0060] After obtaining the sample base, soak the sample base in water, make the sample base in a water-saturated state and then weigh it to obtain the current weight m0. Dry the water-saturated sample base and weigh it to obtain the current weight m1, and calculate the initial porosity A of the base sample N.

[0061]

[0062] After obtaining the initial porosity A, the sample base is subjected to a cycle of freeze-thaw based on the corresponding freezing and thawing temperatures of the obtained sample base. After the freeze-thaw cycle is completed, the sample base is soaked in water, and the sample base is weighed after being in a water-saturated state, and the current weight is obtained as m2. The water-saturated sample base is dried and weighed, and the current weight is obtained as m3, and the increased porosity B is calculated.

[0063]

[0064] In this application, freeze-thaw chambers with different temperatures are set up to simulate the actual freeze-thaw conditions of rocks at different depths, and the water saturation state inside the rocks in nature is simulated according to the water depth, and the deformation of sample N during the freeze-thaw process is monitored, which can more carefully explore the deformation conditions of rocks under freeze-thaw at different depths.

[0065] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Rock freeze-thaw experimental device based on porosity and temperature difference changes, characterized in that: include: An experimental box (10) and a swing mechanism arranged below the experimental box (10), wherein the swing mechanism is used to drive the experimental box (10) to rotate to simulate a slope angle; The test box (10) comprises a first side wall (11) and a second side wall (12) arranged concentrically, wherein the first side wall (11) surrounds a receiving cavity for receiving a sample (N), a freeze-thaw cavity is formed between the first side wall (11) and the second side wall (12), and a temperature isolation plate (13) vertically divides the freeze-thaw cavity into a plurality of freeze-thaw chambers, and the temperature in each freeze-thaw chamber is independently controlled; The strain monitoring system provided in the freeze-thaw chamber is used to monitor the strain of the sample (N) in the corresponding height zone of each freeze-thaw chamber; The water control system arranged in the freeze-thaw cavity is used to control the water level in the freeze-thaw cavity.

2. The rock freeze-thaw experimental device based on porosity and temperature difference change according to claim 1 is characterized in that: Each of the freeze-thaw chambers is provided with a temperature control unit (14) and a temperature measurement unit.

3. The rock freeze-thaw experimental device based on porosity and temperature difference change according to claim 1 is characterized in that: The inner ring of the freeze-thaw chamber is provided with a plurality of longitudinally arranged support screws (16), on which a tray nut is screwed, and a plurality of the temperature isolation plates (13) are overlapped on the tray nut to adjust the height of each freeze-thaw chamber.

4. The rock freeze-thaw experimental device based on porosity and temperature difference change according to claim 1 is characterized in that: The first side wall (11) and the second side wall (12) are made of transparent material.

5. The rock freeze-thaw experimental device based on porosity and temperature difference change according to claim 1 is characterized by: The swing mechanism comprises a base (21), a chassis (22) and a lifting unit (23); the chassis (22) is hinged to the base (21); and the lifting unit (23) pushes the chassis (22) to rotate around the hinge to change the angle between the chassis (22) and the base (21).

6. A rock freeze-thaw experimental method based on porosity and temperature difference changes, using a rock freeze-thaw experimental device based on porosity and temperature difference changes according to any one of claims 1 to 5, characterized in that: include: S10. Obtain a core on the slope of the freeze-thaw zone as a sample (N), divide the sample (N) into a plurality of height lines along the longitudinal direction, and obtain the temperature of each height line interval; S20. Place the sample (N) in the containing chamber, adjust the height lines of each temperature partition to correspond to the sample (N) one by one, and adjust the angle of the swing mechanism to simulate the slope; S30. Inject water of a height H into the freeze-thaw cavity to immerse the sample (N), and after the sample (N) reaches a water saturation state, drain the water from the freeze-thaw cavity; S40. Adjust the temperature of each freeze-thaw chamber, perform a freeze-thaw experiment on the sample (N) for one cycle, inject water with a height of L into the freeze-thaw chamber during the thawing process to maintain a constant water content in the freeze-thaw chamber; obtain the deformation of the sample (N) during the freezing and thawing process; S50. Repeat steps S30-S40 to obtain deformation data of the sample (N) after multiple freeze-thaw cycles.

7. The rock freeze-thaw experimental method based on porosity and temperature difference changes according to claim 6, characterized in that: In step S10, a core is drilled downward perpendicularly to the ground surface of the slope.

8. The rock freeze-thaw experimental method based on porosity and temperature difference changes according to claim 6, characterized in that: In step S40, the initial porosity and the increased porosity of the sample (N) are obtained, and the water injection height L during the thawing process is obtained based on the initial porosity, the increased porosity and the water injection height H. The first water injection height L satisfies: Where A is the initial porosity of sample (N), and B is the increased porosity of sample (N).

9. The rock freeze-thaw experimental method based on porosity and temperature difference changes according to claim 8, characterized in that: In step S10, a portion of the sample (N) is cut as a basic sample (N), and the freeze-thaw temperature corresponding to the basic sample (N) is obtained; Obtain the weight m0 of the basic sample (N) in a water-saturated state and the weight m1 after drying and calculate the initial porosity A of the basic sample (N); A freeze-thaw experiment is performed on the basic sample (N) at a freeze-thaw temperature corresponding to the basic sample (N) for one cycle, and the weight m2 of the basic sample (N) after being in a water-saturated state and the weight m3 after drying are obtained, and the increased porosity B of the basic sample (N) is calculated; The initial porosity and increased porosity of the base sample (N) are the same as the initial porosity and increased porosity of the sample (N).

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