CN113866019B - Direct shear test device suitable for fracture soil with variable size - Google Patents
Direct shear test device suitable for fracture soil with variable size Download PDFInfo
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- CN113866019B CN113866019B CN202111158748.0A CN202111158748A CN113866019B CN 113866019 B CN113866019 B CN 113866019B CN 202111158748 A CN202111158748 A CN 202111158748A CN 113866019 B CN113866019 B CN 113866019B
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- 239000002689 soil Substances 0.000 title claims abstract description 111
- 238000012360 testing method Methods 0.000 title claims abstract description 37
- 238000010008 shearing Methods 0.000 claims abstract description 103
- 238000007596 consolidation process Methods 0.000 claims abstract description 18
- 238000005070 sampling Methods 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims description 23
- 230000005540 biological transmission Effects 0.000 claims description 16
- 238000006073 displacement reaction Methods 0.000 claims description 9
- 230000008569 process Effects 0.000 claims description 8
- 238000012545 processing Methods 0.000 claims description 7
- 238000005527 soil sampling Methods 0.000 claims description 6
- 230000008878 coupling Effects 0.000 claims description 5
- 238000010168 coupling process Methods 0.000 claims description 5
- 238000005859 coupling reaction Methods 0.000 claims description 5
- 238000007660 shear property test Methods 0.000 claims description 3
- 238000003825 pressing Methods 0.000 claims description 2
- 238000003709 image segmentation Methods 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000011159 matrix material Substances 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 238000005457 optimization Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/04—Devices for withdrawing samples in the solid state, e.g. by cutting
- G01N1/08—Devices for withdrawing samples in the solid state, e.g. by cutting involving an extracting tool, e.g. core bit
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0025—Shearing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0605—Mechanical indicating, recording or sensing means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
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- Pathology (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The invention discloses a direct shear test device suitable for fracture soil with variable size, which comprises: the frame comprises a bottom plate and a bracket fixedly connected to the top surface of the bottom plate; the shearing box unit comprises an upper shearing box, a lower shearing box and a plurality of annular sleeves with different sizes; the number of the loading units is two, any loading unit is fixedly connected to the top end of the bracket and used for applying consolidation pressure, and the other loading unit is fixedly connected to the top surface of the bottom plate and used for applying shear stress; the measuring unit comprises a first pressure stress sensor, a second pressure stress sensor and an electronic dial indicator, wherein the first pressure stress sensor and the second pressure stress sensor are respectively and electrically connected with the electronic dial indicator. Meanwhile, a matched sampling device is designed, so that on-site sampling is convenient.
Description
Technical Field
The invention relates to the technical field of strength test of slit soil with a variable sample size, in particular to a direct shear test device suitable for slit soil with a variable sample size.
Background
The fissured soil belongs to special soil and is widely distributed in the south area. Under the action of the dry-wet circulation, wet expansion and shrinkage phenomena can occur in the fractured soil, a large number of macroscopic and microscopic cracks are formed, the cracks can obviously increase the permeability of the soil body, reduce the strength of the soil body and increase the risk of landslide. Therefore, evaluating the strength rule of the fractured soil is an important condition for analyzing the stability of the fractured soil slope.
In the test, the test specimen must be a typical characteristic unit representing the characteristics of the soil body, must be ensured to be uniform, and is representative. This is therefore particularly important for sample size selection. For fracture soils, the selection of sample size is particularly important because the fracture is relatively developed and the selected sample representation necessarily includes fractures. The size of the sample is selected to be smaller, including fewer cracks, and the direct shear test strength is higher; and the test cost is increased if the size of the selected sample is too large, which is inconvenient. Therefore, the method has important significance for selecting reasonable sample sizes for different fracture soil bodies.
At present, the direct shear strength test size of the fractured soil is still a fixed size, and the influence of the size of the sample is not considered, so that the direct shear strength of different sample sizes in the fractured soil cannot be accurately tested, and the research on the strength rule of the fractured soil is seriously hindered.
Disclosure of Invention
The invention aims to provide a direct shear test device suitable for fracture soil with variable size, so as to solve the problems in the prior art, test the direct shear strength of different sample sizes in the fracture soil, select reasonable sample sizes and research the strength rule of the fracture soil.
In order to achieve the above object, the present invention provides the following solutions: the invention provides a direct shear test device suitable for fracture soil with variable size, which comprises: the frame comprises a bottom plate and a bracket fixedly connected to the top surface of the bottom plate; the shearing box unit comprises an upper shearing box, a lower shearing box and a plurality of ring sleeves with different sizes, wherein the ring sleeves are respectively arranged in the upper shearing box and the lower shearing box, the upper shearing box and the lower shearing box are arranged in the bracket, the upper shearing box and the lower shearing box are in contact from top to bottom, and the lower shearing box is in sliding connection with the bottom plate; the number of the loading units is two, any one loading unit is fixedly connected to the top end of the bracket and used for applying consolidation pressure, and the other loading unit is fixedly connected to the top surface of the bottom plate and used for applying shear stress; the measuring unit comprises a first pressure stress sensor, a second pressure stress sensor and an electronic dial indicator, wherein the first pressure stress sensor and the second pressure stress sensor are respectively and electrically connected with the electronic dial indicator, the first pressure stress sensor is arranged between the loading unit and the upper shearing box and positioned on the support, the bottom end of the first pressure stress sensor is fixedly connected with a force transmission cap, the force transmission cap is in sliding connection with the support, the second pressure stress sensor and the electronic dial indicator are both arranged on the bottom plate and positioned on one side of the bottom plate away from the loading unit, the measuring end of the second pressure stress sensor faces the side wall of the upper shearing box, and the measuring end of the electronic dial indicator faces the side wall of the lower shearing box.
Preferably, a plurality of balance screws are fixedly arranged on the bottom plate, and a first level is fixed on the top surface of the bottom plate.
Preferably, a sliding rail is fixedly connected to the top surface of the bottom plate, the sliding rail is located in the support, and the lower shearing box is in sliding connection with the sliding rail.
Preferably, the output end of the loading unit located on the bracket and the first pressure stress sensor are located on the same straight line.
Preferably, the force transmission cap is positioned at the top of the upper shearing box, and the dimension of the force transmission cap is matched with the dimension of the ring sleeve.
Preferably, the loading unit is mainly composed of an electrically controlled propeller.
A soil sampling device comprising: the soil sampler is used for obtaining a soil sample with a reasonable size and placing the soil sample into the annular sleeve; the telescopic assembly comprises a hand-operated jack, and the soil sampler is arranged at the output end of the hand-operated jack; and the fixing assembly is used for fixing the position of the hand-operated jack.
Preferably, the fixed subassembly includes the counter-force crossbeam, the both ends of counter-force crossbeam rigid coupling has the earth anchor respectively, the top surface of counter-force crossbeam is fixed with the second spirit level, the bottom surface of counter-force crossbeam is fixed with hand formula jack, hand formula jack's output rigid coupling has the extension top, the geotome install in the bottom of extension top.
A direct shear test method suitable for fracture soil with variable size is realized by the following steps:
step one: sampling on site, determining a sampling place and extracting a soil sample;
step two: mounting a soil sample, namely slowly pressing the soil sample into the annular sleeve;
step three: applying consolidation pressure until the consolidation pressure is loaded to a preset consolidation pressure, slowly applying the pressure and obtaining data;
step four: applying shear stress, and controlling the loading speed in the application process to realize fast shearing or slow shearing;
step five: and acquiring and processing data to obtain an internal friction angle and cohesive force.
Preferably, in the fifth step, shear stress data and shear displacement data are collected, a relationship curve of shear stress and shear displacement is drawn, a peak point or a stable value on the relationship curve is selected as shear strength, a relationship curve of shear strength and vertical pressure is drawn, and a straight line is drawn according to each point on the graph, so that an internal friction angle and cohesive force can be obtained.
The invention discloses the following technical effects: according to the invention, the annular sleeves with different sizes are placed in the upper shearing box and the lower shearing box, so that the shearing area is changed, a soil sample with reasonable size is placed in the upper shearing box and the lower shearing box, the shearing box is pushed by the loading unit, the consolidation pressure and the shearing stress are applied according to different geological conditions, and the soil sample is horizontally sheared after being consolidated, so that the direct shearing test of the fracture soil with variable size is rapidly and accurately carried out in a construction site. The device is simple and portable, can be brought to a construction site for test, overcomes the difficulty that the traditional direct shear instrument can only shear a single-diameter soil sample, uses the annular sleeves with different inner diameters to realize variable-size shearing, applies consolidation pressure and shearing stress to be provided by the loading unit, does not need to be provided with weights like the traditional direct shear instrument, can be smoothly loaded, and greatly improves the accuracy of the test.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a front view of a direct shear test device for variable size fractured soil according to the present invention;
FIG. 2 is a top view of a direct shear test device suitable for use with variable size fractured soil of the present invention;
FIG. 3 is a top view of a different sized collar of the present invention;
FIG. 4 is a front view of a different sized collar of the present invention;
FIG. 5 is a front view of the soil sampling apparatus of the present invention;
FIG. 6 is a top view of different sized geotomes of the present invention;
FIG. 7 is a front view of different sized soil sampler of the present invention;
wherein, 1 is the bottom plate, 2 is the support, 3 is balanced screw, 5 is automatically controlled propeller, 6 is first pressure stress sensor, 7 is the biography power cap, 8 is the shearing box, 9 is the shearing box down, 10 is the slide rail, 12 is first spirit level, 13 is second pressure stress sensor, 14 is the electron percentage table, 15 is the ring cover, 16 is the earth anchor, 17 is counter-force crossbeam, 18 is the second spirit level, 19 is hand jack, 20 is the extension top, 21 is the geotome.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Example 1
Referring to fig. 1-7, the present embodiment relates to a technique for testing fractured soil, and more particularly to a technique for testing the strength of fractured soil with a varying sample size and a method thereof. Specifically, the embodiment relates to a test of direct shear strength of a fractured soil body, wherein samples with different sample sizes are prepared on site to contain fracture changes, and the change relation of fracture soil sample strength parameters along with the sample sizes is tested, so that accurate fracture soil strength indexes are obtained and are used for guiding engineering practice, and the device specifically comprises the following structures:
the frame comprises a bottom plate 1 and a bracket 2 fixedly connected to the top surface of the bottom plate 1; the bottom plate 1 is the basis of all other parts, and support 2 plays the effect of providing the reaction, and support 2 is four link up and fix the stand on bottom plate 1 and the upper portion a horizontally iron plate is constituteed, and the stand upper end is screw structure for fixed roof.
The shearing box unit comprises an upper shearing box 8, a lower shearing box 9 and a plurality of ring sleeves 15 with different sizes, the ring sleeves 15 with three different sizes are preferable in the embodiment, the ring sleeves 15 are respectively arranged in the upper shearing box 8 and the lower shearing box 9, the upper shearing box 8 and the lower shearing box 9 are arranged in the bracket 2, the upper shearing box 8 and the lower shearing box 9 are contacted with each other from top to bottom, and the lower shearing box 9 is in sliding connection with the bottom plate 1; the upper shearing box 8 is a cuboid, a small cuboid is dug in the middle of the cuboid, the middle small cuboid is communicated, the length and the width of the middle small cuboid are equal, the height is slightly small, the shape above the small cuboid is a square, the ring 15 with different sizes can be put into the middle of the small cuboid to control the size of the center cylinder when shearing, soil samples with different sizes are put into the middle of the small cuboid to be sheared, the lower shearing box 9 is a cuboid, the cuboid is not communicated, the bottom layer is reserved at the bottom of the lower shearing box 9, the dug small cuboid is consistent with the dug small cuboid in the upper shearing box 8, and the ring 15 with different sizes can be put into the middle cylinder to control the size of the center cylinder when shearing so as to put soil samples with different sizes into the middle of the small cuboid to be sheared.
The number of the loading units is two, any loading unit is fixedly connected to the top end of the bracket 2 and used for applying consolidation pressure, and the other loading unit is fixedly connected to the top surface of the bottom plate 1 and used for applying shear stress;
the measuring unit comprises a first pressure stress sensor 6, a second pressure stress sensor 13 and an electronic dial indicator 14, wherein the first pressure stress sensor 6 and the second pressure stress sensor 13 are respectively and electrically connected with the electronic dial indicator 14, the first pressure stress sensor 6 in the middle of the support 2 and the second pressure stress sensor 13 on the right side of the bottom plate 1 are the same, the electronic dial indicator 14 is connected to a computer through a cable so as to record data, the electronic dial indicator 14 is adsorbed on the base 1 through a movable magnetic base and is connected to the computer so as to record data through the cable, the first pressure stress sensor 6 is arranged between a loading unit and the upper shearing box 8 on the support 2, the bottom end of the first pressure stress sensor 6 is fixedly connected with a force transmission cap 7 covering the upper end of a soil sample, the force transmission cap 7 is in sliding connection with the support 2, the second pressure stress sensor 13 and the electronic dial indicator 14 are both arranged on the bottom plate 1, the second pressure sensor 13 is an adjustable front-back pressure stress sensor, the electronic dial indicator 14 is used for measuring displacement, the electronic dial indicator 14 is positioned on the right side of the bottom plate 1, the second pressure sensor 13 is arranged towards the measuring side wall of the electronic shearing box 8, and the side wall of the shearing box is arranged towards the lower side wall 9.
According to the embodiment, the annular sleeves 15 with different sizes are placed in the shearing box, so that the shearing area is changed, a soil sample with reasonable size is placed in the shearing box, the shearing box is pushed by the loading units above and at the left side of the shearing box, confining pressure and shearing stress are applied according to different geological conditions, the soil sample is sheared horizontally after being solidified, and the quick and accurate direct shearing test of the size-variable fractured soil in a construction site is realized.
According to the further optimization scheme, a plurality of balance screws 3, preferably three balance screws, are fixedly arranged on the bottom plate 1, the three balance screws 3 used for adjusting the level on the bottom plate 1 are in an isosceles triangle shape and penetrate through the bottom plate 1, a first level 12 is fixed on the top surface of the bottom plate 1 and used for monitoring whether the bottom plate 1 is level, and the first level 12 is fixed on the bottom plate 1 and keeps level with the bottom plate 1.
According to a further optimization scheme, a sliding rail 10 is fixedly connected to the top surface of the bottom plate 1, the sliding rail 10 is located in the support 2, the lower shear box 9 is in sliding connection with the sliding rail 10, the sliding rail 10 is provided with two grooves parallel to the bottom plate 1, and steel balls for reducing friction force are arranged on the grooves.
Further optimizing scheme, the output end of the loading unit positioned on the support 2 and the first pressure stress sensor 6 are positioned on the same straight line, so that the first pressure stress sensor 6 is directly propped when the output end of the loading unit stretches out.
In a further optimized scheme, the force transmission cap 7 is positioned at the top of the upper shearing box 8, the dimension of the force transmission cap 7 is matched with the dimension of the annular sleeve 15, the force transmission cap 7 is in a truncated cone shape, and the upper part of the force transmission cap 7 is connected and fixed with the first pressure stress sensor 6.
In a further optimization scheme, a loading unit fixed at the upper end of the bracket 2 is identical to a loading unit at the left side of the bottom plate 1, and an electric control propeller 5 is specifically adopted.
A soil sampling device for taking a soil sample of a reasonable size and placing the soil sample into a collar 15, the concrete structure of which comprises:
a soil sampler 21, wherein the soil sampler 21 is used for obtaining a soil sample with a reasonable size and placing the soil sample into the annular sleeve 15;
the telescopic assembly comprises a hand-operated jack 19, and the soil sampler 21 is arranged at the output end of the hand-operated jack 19;
and a fixing assembly for fixing the position of the hand-operated jack 19.
Further optimizing scheme, fixed subassembly includes counter-force crossbeam 17, and the both ends of counter-force crossbeam 17 are fixedly connected with earth anchor 16 respectively, and the top surface of counter-force crossbeam 17 is fixed with second spirit level 18 for confirm the level of counter-force crossbeam 17, the bottom surface of counter-force crossbeam 17 is fixed with hand formula jack 19, and hand formula jack 19's output rigid coupling has extension top 20, and geotome 21 installs in extension top 20's bottom.
According to the embodiment, a matched soil sampling device is utilized to obtain a soil sample with a reasonable size, a ring sleeve 15 with a corresponding size is placed in a shearing box, the soil sample is placed in the ring sleeve 15, confining pressure and shearing stress are applied by two electric control thrusters 5, the soil sample is horizontally slid after being solidified, and then the soil sample is respectively connected with an electronic dial indicator 14, a first pressure stress sensor 6 and a second pressure stress sensor 13 through data wires, so that the displacement and pressure dynamics of a system are monitored in real time, and the size-changing direct shear test can be smoothly carried out.
When the direct shear experimental device suitable for the fracture soil with variable size is used, the operation steps are as follows:
step one: sampling in the field: determining a sampling place, digging a soil pit to the top surface of a preset position by using tools such as manuscript, inserting two ground anchors 16 into two sides of the soil pit, respectively connecting a counter-force beam 17 with the two ground anchors 16 by using bolts, installing a second level 18 above the counter-force beam 17, installing a hand-operated jack 19 below the counter-force beam 17, arranging an lengthened jack 20 below the jack, connecting the jack with a soil sampler 21, and shaking the hand-operated jack 19 to press the soil sampler 21 into soil and then pulling out and leveling the surface of a soil sample when in use;
step two: sample installation: firstly, three balance screws 3 of a bottom plate 1 are adjusted to ensure the bottom plate 1 to be horizontal, a top plate of a bracket 2 and an electric control propeller 5 arranged on the top plate are dismounted, a first pressure stress sensor 6 and a force transmission cap 7 are dismounted, two annular sleeves 15 are sequentially put into a lower shearing box 9 and an upper shearing box 8, then soil in a soil sampler 21 is slowly pressed into the annular sleeves 15, and finally the force transmission cap 7, the first pressure stress sensor 6, the electric control propeller 5 and the top plate on the shearing box are sequentially arranged;
step three: applying consolidation pressure: applying consolidation pressure by using the electric control propeller 5 on the bracket 2 until the consolidation pressure is loaded to a preset consolidation pressure, slowly applying the pressure, obtaining data from the first pressure stress sensor 6, and ensuring that the axis of the electric control propeller 5 is vertical when in use;
the relationship between the readings of the first pressure sensor 6 on the support 2 and the preset consolidation pressure is as follows:
F 1 ＝σA s -F
wherein: F1F 1 Is that A reading (N) of the first pressure stress sensor 6; sigma is the preset consolidation pressure (kPa), A S Shear area (cm) of soil sample 2 ) The method comprises the steps of carrying out a first treatment on the surface of the F is the force (N) generated by the weight of the first pressure sensor 6 and the force transmitting cap 7.
Step four: applying shear stress: the electric control propeller 5 on the bottom plate 1 is used for applying shearing stress, and the loading speed can be controlled to realize fast shearing or slow shearing;
step five: data acquisition and processing: the shear stress data is obtained through a second pressure stress sensor 13 on the right side of the bottom plate 1, the shear displacement data is obtained through an electronic dial indicator 14, the shear stress is taken as an ordinate, the shear displacement is taken as an abscissa, a relation curve of the shear stress and the shear displacement is drawn, and a peak point or a stable value on the relation curve is selected as the shear strength S;
and drawing a relation curve of the shear strength and the vertical pressure by taking the shear strength S as an ordinate and the vertical pressure P as an abscissa, and drawing a straight line according to each point on the graph to obtain an internal friction angle and cohesive force.
Example 2
The difference from the above embodiment 1 is that this embodiment provides a method for measuring a shear Area (AS) of a soil sample, so that a specific value of the shear area can be obtained quickly in the above embodiment, which is achieved by the following steps:
(1) And (3) collecting images of the structural surface of the fractured soil:
and photographing the surface of the sheared fracture soil structure surface at the bright place by using a digital camera. Before photographing, the surface of the structural surface of the fractured soil is required to be cleaned, meanwhile, a graduated scale is used as a reference object to be placed beside, and the graduated scale is contained in the picture. When photographing, the lens of the digital camera vertically focuses on the fracture soil structural surface, a close-range mode is selected for photographing, errors caused by angles are avoided, and a clear color picture of the fracture soil structural surface is obtained.
(2) Clipping and filling of pictures:
in the slit soil structural surface color picture taken, except the slit soil structural surface itself, a scale serving as a reference and redundant surrounding parts are in the picture, and these ranges are not calculated when the slit soil structural surface shearing area is counted, so that these ranges need to be cut. In this way, an image processing step is performed to fill the unnecessary portion with a darker color than the cutout portion.
This step can be implemented in image processing software such as Adobe Photoshop, MATLAB, etc. In practical research, programming is performed based on MATLAB software, but in order to make the operation process popular, description will be given by taking Adobe Photoshop (Adobe Photoshop CS chinese edition) software which is more widely used as an example.
The specific operation steps are as follows: cutting the picture by using a rectangular frame selecting tool in the toolbox to extract a fracture soil structural surface; the investigation region is then extracted precisely using the paint bucket tool in the tool box in combination with the polygonal lasso tool in the tool box and the non-investigation region is filled in with a dark color.
(3) Converting the color picture into a gray-scale picture:
this step utilizes image segmentation techniques in digital image processing. The technology is to divide the image to be processed into specific areas with unique properties according to the research requirement, and further propose the technology and process of the target of interest of the researcher. As a key step of image processing and image analysis, image segmentation techniques are mainly classified into the following categories according to the method employed: threshold-based, region-based, edge-based, theory-specific image segmentation techniques, and the like. The image segmentation technique that is currently more commonly used is a gray scale threshold based method. Because the gray level threshold value is based, the collected slit soil structural surface color photo must be subjected to gray level treatment, so that the original color picture is changed into a gray level picture. In this process, the gray information of the image is unchanged.
In the process of converting a surface color picture of a slit soil structure surface cut by a camera into a gray-scale picture, one gray-scale image is a matrix, each number in the matrix corresponds to each pixel in the image, the number size in the matrix represents the gray value of the pixel, and the value range is 0-255. Wherein 0 shows black in the grayscale image, and 255 represents white.
This step may be implemented in image processing software such as Adobe Photoshop, MATLAB, etc., for example, in Adobe Photoshop CS (chinese version) software, and the specific operation steps are: the conversion of color images to grayscale images can be accomplished using an image (I) → adjustment (a) → Black & White … tool in the menu bar.
(4) Selecting a gray level threshold:
in the shearing process of the fracture soil structural surface direct shear test, the contact part of the structural surface is broken by friction, fragments are generated, scratches appear, and compared with the surrounding shearing part, the color is generally lighter, and the statistics is based on the conventional shearing area measurement method. In this embodiment, the image segmentation technique is also used to extract the sheared (relatively light color) parts of the fracture soil structure surface image.
The determination of the gray level threshold value requires that the histogram is visually checked according to a plurality of observation rules to find the minimum value of the gray level of the sheared (relatively light color) part so as to determine the final threshold value. This step may be implemented in image processing software such as Adobe Photoshop, MATLAB, etc., for example, in Adobe Photoshop CS (chinese version) software, and the specific operation steps are: and clicking a cut (relatively light color) part in the gray-scale picture by using a magic bar tool in the toolbar, and displaying the gray value of the part in a histogram at the upper right part of the window. Because the brighter the region the greater the gray value, the more often the cut (relatively lighter color) region in the picture is not a fixed value, the process must be repeated multiple times until the gray minimum, i.e., gray threshold, for the cut (relatively lighter color) region is found.
(5) Converting the gray-scale picture into a black-and-white binary picture:
the conversion aims at extracting a structure surface shearing part area in an image, and the principle is that the gray scale threshold value selected in the step (4) is used for processing to convert a slit soil structure surface gray scale picture into a black-white binary picture, wherein a white area is a shearing part, and a black area is a non-shearing part.
This step may be implemented in image processing software such as Adobe Photoshop, MATLAB, etc., for example, in Adobe Photoshop CS (chinese version) software, and the specific operation steps are: the conversion from gray-scale picture to black-and-white binary picture can be realized by using the tool from image (I) to threshold (T) in menu bar, a dialog box appears after clicking, the gray threshold selected in step (4) is filled into the threshold color level, and the white part in the figure is the shearing part in the crack soil structural plane direct shear test.
(6) According to the percentage of the white part (shearing part) accounting for the whole picture, namely the shearing area percentage of the fracture soil structural surface direct shear test:
according to the step (4), the gray-scale picture of the structural surface of the slit soil is formed by arranging and combining a large number of pixel points in a matrix mode, and if the picture is observed by naked eyes through a magnifying glass, the small lattices which are orderly arranged can be seen, wherein each small lattice is one pixel point. The pixel point is the minimum display unit in the picture, the shearing area percentage can be obtained by calculating the pixel point percentage, and the mode is convenient for operation on a computer, improves the working efficiency and reduces human errors.
The step can be implemented in image processing software such as Adobe Photoshop and MATLAB, for example, in Adobe Photoshop CS (chinese edition) software, and the cut area percentage of the fracture soil structural surface direct shear test can be calculated in a histogram information window.
(7) Actual area of the fracture soil structure surface:
according to the scale adopted during photographing, the size scale of the fracture soil structural surface in the picture can be obtained, and then the actual area of the fracture soil structural surface can be calculated.
(8) And (3) solving the shearing area of the fracture soil structural surface shearing test:
the method comprises the steps of obtaining the shearing area in the direct shearing test of the fracture soil structure surface according to an image method, and obtaining the shearing area of the fracture soil structure surface shearing test based on the parameters, wherein the percentage of the shearing part to the total area and the actual total area of the fracture soil structure surface are measured in the steps (6) and (7).
Through the steps, the measurement of the shearing area in the fracture soil structural surface direct shear test is realized.
In the description of the present invention, it should be understood that the terms "longitudinal," "transverse," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate or are based on the orientation or positional relationship shown in the drawings, merely to facilitate description of the present invention, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (8)
1. Direct shear test device suitable for crack soil of variable size, characterized in that includes:
the frame comprises a bottom plate (1) and a bracket (2) fixedly connected to the top surface of the bottom plate (1);
the shearing box unit comprises an upper shearing box (8), a lower shearing box (9) and a plurality of annular sleeves (15) with different sizes, wherein the annular sleeves (15) are respectively arranged in the upper shearing box (8) and the lower shearing box (9), the upper shearing box (8) and the lower shearing box (9) are arranged in the bracket (2), the upper shearing box (8) and the lower shearing box (9) are in contact from top to bottom, and the lower shearing box (9) is in sliding connection with the bottom plate (1);
the number of the loading units is two, any loading unit is fixedly connected to the top end of the bracket (2) and used for applying consolidation pressure, and the other loading unit is fixedly connected to the top surface of the bottom plate (1) and used for applying shear stress;
the measuring unit comprises a first pressure stress sensor (6), a second pressure stress sensor (13) and an electronic dial indicator (14), wherein the first pressure stress sensor (6) and the second pressure stress sensor (13) are respectively and electrically connected with the electronic dial indicator (14), the first pressure stress sensor (6) is arranged between the loading unit on the support (2) and the upper shearing box (8), a force transmission cap (7) is fixedly connected to the bottom end of the first pressure stress sensor (6), the force transmission cap (7) is in sliding connection with the support (2), the second pressure stress sensor (13) and the electronic dial indicator (14) are both arranged on the bottom plate (1) and are positioned on one side of the bottom plate (1) away from the loading unit, the measuring end of the second pressure stress sensor (13) faces the side wall of the upper shearing box (8), and the measuring end of the electronic dial indicator (14) faces the side wall of the lower shearing box (9);
a plurality of balance screws (3) are fixedly arranged on the bottom plate (1), and a first level meter (12) is fixedly arranged on the top surface of the bottom plate (1);
the output end of the loading unit positioned on the bracket (2) and the first pressure stress sensor (6) are positioned on the same straight line.
2. The direct shear test device suitable for fracture soil of varying size according to claim 1, wherein: the top surface of the bottom plate (1) is fixedly connected with a sliding rail (10), the sliding rail (10) is positioned in the bracket (2), and the lower shearing box (9) is in sliding connection with the sliding rail (10).
3. The direct shear test device suitable for fracture soil of varying size according to claim 1, wherein: the force transmission cap (7) is positioned at the top of the upper shearing box (8), and the size of the force transmission cap (7) is matched with the size of the ring sleeve (15).
4. A direct shear test device suitable for use in a variable-size fractured soil according to any one of claims 2-3, wherein: the loading unit is mainly composed of an electric control propeller (5).
5. A soil sampling device based on the direct shear test device for variable-size slit soil according to claim 1, comprising:
the soil sampler (21) is used for obtaining a soil sample with a reasonable size and placing the soil sample into the annular sleeve (15);
the telescopic assembly comprises a hand-operated jack (19), and the soil sampler (21) is arranged at the output end of the hand-operated jack (19);
and the fixing assembly is used for fixing the position of the hand-operated jack (19).
6. The soil sampling apparatus of claim 5, wherein: the fixed subassembly includes counter-force crossbeam (17), the both ends rigid coupling of counter-force crossbeam (17) have earth anchor (16) respectively, the top surface of counter-force crossbeam (17) is fixed with second spirit level (18), the bottom surface of counter-force crossbeam (17) is fixed with hand formula jack (19), the output rigid coupling of hand formula jack (19) has extension top (20), geotome (21) install in the bottom of extension top (20).
7. The direct shear test method suitable for the size-variable fractured soil is based on the direct shear test device suitable for the size-variable fractured soil, and is characterized by comprising the following steps of:
step one: sampling on site, determining a sampling place and extracting a soil sample;
step two: mounting a soil sample, and slowly pressing the soil sample into the annular sleeve (15);
step three: applying consolidation pressure until the consolidation pressure is loaded to a preset consolidation pressure, slowly applying the pressure and obtaining data;
step four: applying shear stress, and controlling the loading speed in the application process to realize fast shearing or slow shearing;
step five: and acquiring and processing data to obtain an internal friction angle and cohesive force.
8. The direct shear test method for variable-size fractured soil according to claim 7, wherein: in the fifth step, the shear stress data and the shear displacement data are collected, a relationship curve of the shear stress and the shear displacement is drawn, a peak value or a stable value on the relationship curve is selected as the shear strength, the relationship curve of the shear strength and the vertical pressure is drawn, and a straight line is drawn according to each point on the graph, so that the internal friction angle and the cohesive force can be obtained.
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| CN201909741U (en) * | 2010-12-29 | 2011-07-27 | 中国科学院武汉岩土力学研究所 | Direct shear test system for saturated rock-soil samples |
| WO2019109633A1 (en) * | 2017-12-04 | 2019-06-13 | 深圳大学 | Method and symmetrical direct shear apparatus for in-situ testing of pile-soil interface shear strength |
| CN112268776A (en) * | 2020-11-17 | 2021-01-26 | 南京大学 | Preparation method of fractured soil compressive strength test sample |
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| CN201909741U (en) * | 2010-12-29 | 2011-07-27 | 中国科学院武汉岩土力学研究所 | Direct shear test system for saturated rock-soil samples |
| WO2019109633A1 (en) * | 2017-12-04 | 2019-06-13 | 深圳大学 | Method and symmetrical direct shear apparatus for in-situ testing of pile-soil interface shear strength |
| CN112268776A (en) * | 2020-11-17 | 2021-01-26 | 南京大学 | Preparation method of fractured soil compressive strength test sample |
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