Physical model of ramp with anti-dip weak plane locking segment and its instability failure experiment method

Abstract

The application provides a kind of containing anti-inclined weak face locking segment type slope physical model and its instability failure experiment method, and relates to the technical field of geomechanics model preparation.The model is a pentagon block, including upper part block I and lower part block II;the right half of block I and the lower half of block II simulate bedrock, the left half of block I and the upper half of block II simulate sliding body;the middle fissure of block I simulates rear edge tension fissure;the front edge creep segment is embedded in block II to simulate the lower end of rear edge tension fissure and the higher end of front edge creep segment, and the middle part of locking segment is between them;block I and block II are separated by acrylic plate, and the fissure between block I and block II simulates "weak face", which penetrates the whole block and passes through the locking segment.The model and method study the deformation and failure evolution process of the locking segment type slope containing anti-inclined weak face, analyze the influence mechanism of weak face structure in locking segment on the failure and instability of locking segment type slope, and reveal the unlocking mechanism of the locking segment type slope containing anti-inclined weak face.

Description

Technical Field

[0001] This invention relates to the field of geomechanical model preparation technology, and in particular to a physical model of a slope with a locked section containing a weak anti-dip surface and its instability and failure experimental method. Background Technology

[0002] Among numerous catastrophic landslides, locked-segment landslides are one of the most common types. The locked segment refers to the section of the slope where the sliding surface is not yet connected during deformation and failure, where stress concentration occurs, and which provides critical load-bearing capacity. Slopes where the overall stability is controlled by the locked segment are collectively referred to as locked-segment slopes. Before the instability of a locked-segment slope, the locked segment is subjected to slow, concentrated shear stress or stress corrosion, containing enormous strain energy. When brittle fracture occurs in the locked segment, the strain energy is converted into kinetic energy of the slope, leading to a rapid, instantaneous initiation of the landslide. Therefore, the brittle failure of this type of slope is typically characterized by high initiation speed, suddenness, and severe damage, often causing significant casualties and property losses. Thus, research on the instability and failure mechanism of locked-segment slopes has significant practical importance and is an urgent social need for slope instability prediction and disaster prevention.

[0003] Previous studies have classified locked-segment slopes based on the relationship between the sliding surface and the stratigraphic attitude, as well as the occurrence form of the locked segment. Based on the relationship between the sliding surface and the stratigraphic attitude, they are classified as: cross-strata oblique shear, bedding-parallel direct shear, retaining wall, homogeneous rock bridge, and supported arch. Based on the occurrence form of the locked segment, they are classified as: three-segment, retaining wall buckling, and thrust. Although numerous physical model experiments, numerical simulations, and theoretical studies have been conducted on different types of locked-segment slopes, greatly advancing the research on the instability and failure mechanisms of locked-segment slopes, insufficient consideration has been given to the internal structure of the locked segment. Previous studies often simplified the locked segment to a complete rock block that controls slope stability. Research shows that natural locked segments are essentially large-sized rock masses, typically containing weak surfaces such as bedding and joints. Their internal structure has a significant impact on the instability and fracturing evolution mechanism and failure mode of the locked segment. Therefore, conducting research on the instability mechanism of locked-segment slopes containing reverse-dip weak surfaces is of great significance for deeply revealing the instability and failure mechanism of locked segments and promoting slope instability prediction and disaster prevention. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a physical model of a slope with a locking section containing a weak anti-dip surface and an experimental method for its instability and failure, thereby realizing the experimental preparation of the physical model of the slope with a locking section containing a weak anti-dip surface and the instability and failure of the model.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] On one hand, the present invention provides a physical model of a slope with a locking section containing a weak anti-dip surface. The physical model is a pentagonal block, including an upper block I and a lower block II. The right half of block I and the lower half of block II simulate bedrock, and the left half of block I and the upper half of block II simulate landslides. The cracks in block I simulate the trailing edge tensile fractures, and the depth of the trailing edge tensile fractures is set as the critical depth. An acrylic plate is embedded in block II to simulate the leading edge creep section, and the middle part between the lower end of the trailing edge tensile fracture and the higher end of the leading edge creep section is the locking section. Block I and block II are separated by an acrylic plate, and the crack between block I and block II simulates a "weak surface". The weak surface runs through the entire block and passes through the locking section.

[0007] On the other hand, the present invention also provides an experimental method for the instability failure of a physical model of a slope containing a reverse-dipping weak surface and a locked section, comprising the following steps:

[0008] (I) Making the model box

[0009] 1. Make an open-top pentagonal prism acrylic mold;

[0010] 2. Adhere acrylic sheets of different sizes to the upper right, lower left, and middle parts of the mold respectively;

[0011] 3. Allow to stand at room temperature until the colloid has completely solidified before use;

[0012] (II) Preparation of slope specimens containing a locking section with a weak anti-dip surface

[0013] 1. Considering parameters such as elastic modulus, Poisson's ratio, and compressive strength, select raw materials such as ordinary Portland cement, quartz sand, gypsum powder, and water according to the weight ratio;

[0014] 2. After completing the raw material proportioning, pour the above raw materials into the mold box to make block I and block II have the same height. Vibrate them thoroughly under the action of the vibrating table to make them dense, and use a level to correct the upper surface.

[0015] 3. After molding the sample, cure and demold. When demolding, remove the upper and middle acrylic plates of the block, leaving the lower acrylic plate inside the block, which is called the "rear edge tensile crack", "locking section weak surface" and "leading edge creep section". After demolding, cure under the set conditions.

[0016] (III) Spraying with speckles

[0017] After the specimen is cured, it is taken out and the specimen surface is completely dry. Strain gauges are fixed in the locking section and at the front end of the tensile crack at the rear edge. To increase the contrast and facilitate speckle identification, a layer of white paint is sprayed on the specimen surface after the strain gauges are arranged. Then, a stiff brush is dipped in ink and the brush is moved to make the ink splash onto the specimen surface, presenting black, uniform, and dense spots.

[0018] (iv) Conduct instability and failure experiments on the physical model of a slope with a weak anti-dip surface and a locked section, and study the deformation and failure of the slope with a weak anti-dip surface and a locked section.

[0019] The specimen of the inclined slope with a weak anti-dip section was placed on the load loading device. The normal displacement of the left and right ends and the lower side of the specimen was restricted by a steel plate. The load was applied to the top of the specimen in a slow step-load manner to simulate the stress state of the inclined slope under gravity until the specimen failed. During the process, a camera was set up in front of the loading device with the focus on the middle of the inclined section to record the instability and failure process. Strain gauges were attached to the monitoring position of the specimen and connected to a strain monitoring instrument to detect the deformation of the specimen.

[0020] (V) Analysis of Experimental Results

[0021] Experimental data was extracted by capturing images from experimental videos using digital image correlation techniques. The data was then analyzed and corrected in conjunction with data obtained from a strain monitoring instrument. The correction process was divided by the appearance of cracks in the locking section: before the cracks appeared, the stress-strain monitoring data was used as a benchmark to calibrate the DIC measurement data; after the cracks appeared, the calibrated DIC data was used as a benchmark to recalibrate the stress-strain monitoring data, and the experimental results were analyzed based on the corrected data.

[0022] The beneficial effects of adopting the above technical solution are as follows: The physical model of a slope with a weak anti-dip surface and its instability failure experimental method provided by this invention can fully demonstrate the dynamic process of crack propagation, development, and final failure in the weak anti-dip surface locked section. During failure, it exhibits extremely strong brittleness accompanied by high-speed sliding of the slope body, which corresponds one-to-one with the actual deformation failure processes such as "creep" and "brittle shear" of the locked section with a weak anti-dip surface. It can be used to study the unlocking mechanism of the locked section slope with a weak anti-dip surface. Furthermore, the model preparation method is simple and easy to implement, economical in materials, and highly feasible. In summary, this physical model experimental method for a slope with a weak anti-dip surface and its associated locking section is a relatively reasonable and ideal experimental research method for studying the unlocking mechanism of locked section slopes.

[0023] Based on this model, the dynamic process of crack generation, development and eventual failure of the locking section with a weak anti-dip surface can be displayed in detail. Combined with stress-strain monitoring, digital image correlation (DIC) and other technologies, the deformation and failure evolution process of the locking section with a weak anti-dip surface can be studied, the influence mechanism of the weak surface structure in the locking section on the failure and instability of the locking section type slope can be analyzed, and the unlocking mechanism of the locking section type slope with a weak anti-dip surface can be revealed. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a physical model of a slope with a weak surface locking section provided in an embodiment of the present invention;

[0025] Figure 2This is a schematic diagram of the dimensions of a model box provided in an embodiment of the present invention, wherein (a) is a front view and (b) is a side view;

[0026] Figure 3 This is a schematic diagram of a physical model of a slope with a weak surface and a locking segment, provided in an embodiment of the present invention.

[0027] In the figure: 1. Block I; 2. Block II; 3. Trailing edge tensile crack; 4. Leading edge creep section; 5. Locking section; 6. Weak surface. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0029] In this embodiment, a physical model of a slope with a weak, anti-sloping, locked section is simplified based on an actual geological prototype, and has practical research significance and value. For example... Figure 1 As shown, the physical model is a pentagonal block, including an upper block I1 and a lower block II2. The right half of block I1 and the lower half of block II2 simulate bedrock, while the left half of block I1 and the upper half of block II2 simulate landslides. The fractures in block I1 simulate the rear-edge tensile fracture 3. It should be noted that this invention mainly focuses on the influence of weak surfaces within the locking section on the strength of the locking section, so the depth of the rear-edge tensile fracture 3 is set to a critical depth (approximately half the slope height). In this embodiment, the fracture 3 in block I has an inclination angle of approximately 85°, a length of approximately 15cm, and a thickness of approximately 4mm. An acrylic plate is embedded in block 2 to simulate the leading-edge creep section 4. In this embodiment, the acrylic plate has an inclination angle of approximately 15°, a length of approximately 31cm, and a thickness of approximately 4mm. The middle part between the lower end of the rear-edge tensile fracture 3 and the higher end of the leading-edge creep section 4 is the locking section 5. Figure 1 As shown in the label; the crack between block I1 and block II2 simulates a weak surface 6, which penetrates the entire block and passes through the locking section 5. In this embodiment, the weak surface has an inclination angle of approximately 5° and a length of approximately 35cm.

[0030] In this embodiment, a failure and instability test method for a physical model of a slope with a locked section containing a weak anti-sloping surface includes the following steps:

[0031] (a) Production Figure 2 The model box shown

[0032] 1. Make an open-top pentagonal prism acrylic mold;

[0033] 2. Adhere acrylic sheets of different sizes to the upper right, lower left, and middle parts of the mold respectively;

[0034] The dimensions of the acrylic sheet are as follows;

[0035] Precast acrylic panel 3: 15cm×16cm×4mm

[0036] Precast acrylic sheet 4: 31cm×16cm×4mm

[0037] Precast acrylic panel 6: 35cm × 16cm × 4mm

[0038] 3. Allow to stand at room temperature until the colloid has completely solidified before use;

[0039] (II) Preparation of slope specimens containing a locking section with a weak anti-dip surface

[0040] 1. Considering parameters such as elastic modulus, Poisson's ratio, and compressive strength, ordinary Portland cement, quartz sand, gypsum powder, and water are selected as raw materials and mixed according to the following weight ratio:

[0041] Table 1 Raw Material Proportions

[0042] Proportion 5 13 4 1

[0043] The cement is ordinary Portland cement, model P.O42.5; the quartz sand is 60 mesh; the gypsum powder is building material gypsum powder; and the water is ordinary purified water.

[0044] 2. After completing the raw material proportioning, pour the above raw materials into the mold box to make block I and block II have the same height. Vibrate them thoroughly under the action of the vibrating table to make them dense, and use a level to correct the upper surface.

[0045] 3. After molding, the sample is cured for 48 hours before demolding. During demolding, the upper and middle acrylic plates of the block are removed, while the lower acrylic plate remains in the block, which is called the "rear edge tensile crack", "locking section weak surface", and "front edge creep section". After demolding, the sample is cured for 28 days under the conditions of set temperature 17-23℃ and humidity above 95%.

[0046] (III) Spraying with speckles

[0047] After the specimen curing is completed, it is removed and, once the specimen surface is completely dry, strain gauges are fixed at the locking section and the front end of the tensile crack at the rear edge. To increase contrast and facilitate speckle identification, after the strain gauges are arranged, a layer of white paint is sprayed onto the specimen surface, and ink is applied using a stiff brush. The brush is then moved to splash the ink onto the specimen surface, creating uniform, dense black spots approximately 2 mm in diameter. Figure 3 As shown, let stand for 2 hours.

[0048] (iv) Conduct instability and failure experiments on the physical model of a slope with a weak anti-dip surface and a locked section, and study the deformation and failure of the slope with a weak anti-dip surface and a locked section.

[0049] The specimen of the inclined slope with a weak anti-slope section was placed on the load loading device. The normal displacement of the left and right ends and the lower side of the specimen was restricted by steel plates. The load was applied to the top of the specimen in a slow stepwise loading method to simulate the stress state of the inclined slope under gravity. The loading condition was 0.25MPa / 2h until the specimen failed. During the process, a camera was set up 35cm in front of the loading device with the focus on the middle of the inclined section to record the experimental process. Strain gauges were attached to the monitoring position of the specimen and connected to a strain monitoring instrument to detect the deformation of the specimen.

[0050] (V) Analysis of Experimental Results

[0051] Analyze the experimental results; extract experimental data by capturing images from the experimental video using digital image correlation techniques, and analyze and correct the experimental data by combining the data obtained from the strain monitoring instrument; and analyze the experimental results based on the corrected data.

[0052] Digital image correlation (DIC) is a high-precision measurement method that obtains deformation information of a region by calculating the relative changes in point positions based on images before and after deformation. Its basic principle is as follows: the selected region in the image before deformation is processed into grayscale and divided into multiple subsets of equal size. Then, these subsets are tracked in subsequent deformed images, and the deformation vector of the region is calculated using the vertical and horizontal displacement components of the subset centers. The displacement of the subset center has the greatest impact on the accuracy of this measurement method. Spraying speckle can improve the recognition level of the grayscale processed image, improve the subset capture accuracy, and thus improve the monitoring accuracy of this technique.

[0053] Before analyzing the test results, experimental data correction is required. Before cracks appear, the data obtained from DIC technology is verified and corrected using data from a stress-strain monitoring instrument. After cracks appear, the stress-strain monitoring instrument data may be biased or missing due to the crack penetrating the strain gauge. Therefore, the data obtained from DIC technology after correction is needed to fill in and correct the missing monitoring data.

[0054] In this embodiment, under a loading condition of 0.25 MPa / 2 h, the sample failed after 48 h. The experimental phenomena were highly consistent with the actual failure of the lock-type slope with a weak anti-dip surface. The lock-type section as a whole exhibited compressive-shear failure, with cracks developing from the creep section at the leading edge and the tensile crack at the trailing edge towards the lock-type section. Phenomena such as "crack misalignment" appeared at the weak anti-dip surface. The horizontal displacement of the cracks showed a stepped evolution during the accelerated creep stage, which corresponds to the instability failure characteristics of a natural lock-type slope with a weak anti-dip surface. This proves that the experimental method is an ideal experimental method for studying the failure of lock-type slopes with weak anti-dip surfaces. It can be used to analyze the influence mechanism of the weak surface structure within the lock-type section on the failure and instability of the lock-type slope and to reveal the unlocking mechanism of lock-type slopes with weak anti-dip surfaces.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A physical model of a slope with a locking section containing a weak anti-dip surface, characterized in that: The physical model is a pentagonal block, consisting of an upper block I and a lower block II. The right half of block I and the lower half of block II simulate bedrock, while the left half of block I and the upper half of block II simulate landslides. The cracks in block I simulate tensile fractures at the rear edge. An acrylic plate is embedded in block II to simulate the creep section at the front edge. The middle part between the lower end of the tensile fracture at the rear edge and the higher end of the creep section at the front edge is the locking section. Block I and block II are separated by an acrylic plate. The crack between block I and block II simulates a "weak surface," which runs through the entire block and passes through the locking section.

2. The physical model of a slope with a locking section containing a weak anti-dip surface according to claim 1, characterized in that: The trailing edge tensile fracture depth is set to the critical depth.

3. An experimental method for the instability failure of a physical model of a slope with a weak anti-dip surface and a locked section, based on the physical model of the slope with a weak anti-dip surface and a locked section as described in claim 1, characterized in that: Includes the following steps: (a) Making the model box (II) Preparation of slope specimens with locking sections of weak anti-dip surfaces (iii) Spraying speckle patterns onto the sample (iv) Conduct instability and failure experiments on the physical model of the slope with the anti-dip weak surface locked section, and study the deformation and failure of the slope with the anti-dip weak surface locked section; The specimen of the inclined slope with a weak anti-dip section was placed on the load loading device. The normal displacement of the left and right ends and the lower side of the specimen was restricted by a steel plate. The load was applied to the top of the specimen in a slow step-load manner to simulate the stress state of the inclined slope under gravity until the specimen failed. During the process, a camera was set up in front of the loading device with the focus on the middle of the inclined section to record the instability and failure process. Strain gauges were attached to the monitoring position of the specimen and connected to a strain monitoring instrument to detect the deformation of the specimen. (v) Analyze the experimental results.

4. The instability and failure test method of the physical model of a slope with a locked section containing a weak anti-dip surface as described in claim 3, characterized in that: The specific method for making the model box is as follows: 1) Make an open-top pentagonal prism acrylic mold; 2) Adhere acrylic sheets of different sizes to the upper right, lower left, and middle parts of the mold respectively; 3) Let it stand at room temperature until the colloid is completely solidified before use.

5. The instability and failure test method of the physical model of a slope with a locked section containing a weak anti-sloping surface according to claim 4, characterized in that: The specific method for preparing the slope specimen containing the anti-dip weak surface locking section is as follows: (1) Considering parameters such as elastic modulus, Poisson's ratio, and compressive strength, ordinary silicate cement, quartz sand, gypsum powder, and water are selected as raw materials and mixed according to the weight ratio; (2) After completing the raw material proportioning work, pour the above raw materials into the mold box to make block I and block II have the same height. Vibrate them fully under the action of the vibration table to make them dense, and use a level to correct the upper end face. (3) Curing and demolding of the sample after molding. When demolding, remove the upper and middle acrylic plates of the block, and leave the lower acrylic plate in the block, which are the "rear edge tensile crack", "locking section weak surface" and "front edge creep section". After demolding, cure under the set conditions.

6. The instability and failure test method for a physical model of a slope with a locked section containing a weak anti-sloping surface according to claim 5, characterized in that: The specific method for spraying speckle patterns onto the sample is as follows: After the specimen is cured, it is taken out and the specimen surface is completely dry. Strain gauges are fixed in the locking section and at the front end of the tensile crack at the rear edge. To increase the contrast and facilitate speckle identification, a layer of white paint is sprayed on the specimen surface after the strain gauges are arranged. Then, a stiff brush is dipped in ink and the brush is moved to make the ink splash onto the specimen surface, presenting black, uniform, and dense spots.

7. The instability and failure test method for a physical model of a slope with a locked section containing a weak anti-dip surface as described in claim 6, characterized in that: The specific method for analyzing the experimental results is as follows: Experimental data were extracted by capturing images from experimental videos using digital image correlation techniques, and the data obtained from the strain monitoring instrument were then analyzed and corrected.

8. The instability and failure test method of the physical model of a slope with a locked section containing a weak anti-dip surface according to claim 7, characterized in that: Before analyzing the experimental results, the method requires calibration of the experimental data. The calibration process is divided by the appearance of cracks in the locking section: before the cracks appear, the DIC measurement data is calibrated based on the stress and strain monitoring data; after the cracks appear, the stress and strain monitoring data is recalibrated based on the calibrated DIC data, and the experimental results are analyzed based on the calibrated data.

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