CN114441262A - Device and method for preparing undisturbed soil sample for hollow cylinder torsional-shear triaxial test - Google Patents
Device and method for preparing undisturbed soil sample for hollow cylinder torsional-shear triaxial test Download PDFInfo
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- CN114441262A CN114441262A CN202210053380.XA CN202210053380A CN114441262A CN 114441262 A CN114441262 A CN 114441262A CN 202210053380 A CN202210053380 A CN 202210053380A CN 114441262 A CN114441262 A CN 114441262A
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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
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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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
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
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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
- G01N3/22—Investigating strength properties of solid materials by application of mechanical stress by applying steady torsional forces
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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
Abstract
The invention relates to a device and a method for preparing an undisturbed soil sample in a hollow cylinder torsional shear triaxial test, wherein the device comprises a rotatable dowel bar, a drill bit, a cylindrical soil sample fixer and a bracket support with a base, the cylindrical soil sample fixer is arranged on a bracket support of the bracket support, the rotatable dowel bar and the drill bit are arranged on a cross beam of the bracket support, the cylindrical sample fixer is formed by assembling a half-open film, circular steel sheets at two ends and a fixed steel sheet support, the force transmission device is formed by assembling the dowel bar and the circular drill bit, a rotatable fixed sleeve is arranged on a central axis of the cross beam, and the axes of the rotatable dowel bar, the drill bit and the circular sample fixer are coincided with the axis of the bracket support with the base. The device can make the height of original state soil sample fixer unanimous with the height of sample, can improve the roughness of cylindrical original state soil sample, effectively solves the problem that hollow cylinder sample preparation precision is low, the drilling is difficult, system appearance inefficiency, original state soil sample disturbance are big.
Description
Technical Field
The invention belongs to a soil sample preparation device for geotechnical tests, and particularly relates to a preparation device and a preparation method for an undisturbed soil sample for a simple dynamic and static hollow cylinder torsional shear triaxial test.
Background
In the scientific research and engineering construction process of geotechnical engineering, geotechnical tests are often used as a main research method in geotechnical engineering. In engineering practice, after the soil body structure is subjected to external force, unfavorable geological phenomena such as strength attenuation, deformation increase and the like occur, and the method has important value for judging whether the soil body structure is stable, the ultimate strength and the maximum deformation in foundation engineering and roadbed engineering in engineering. Therefore, the geotechnical test method also becomes a key link for scientific research and engineering construction.
Generally speaking, geotechnical tests usually carry out research on two objects, namely an undisturbed soil sample and a remolded soil sample, and a large number of scientific research and engineering construction cases show that the test result of the undisturbed soil sample is closer to the actual stress condition of a soil body in engineering construction. With the further deep understanding of the actual stress state of the soil body by scientific researchers, the discovery of the actual stress state of the soil body is a very complicated process, and a dynamic and static hollow cylindrical torsional shear triaxial test technology is developed for further deep research on the mechanical characteristics of the soil body under the complex stress condition. However, the research object of the dynamic and static hollow cylinder torsional shear triaxial test is a hollow triaxial soil sample, and compared with the traditional solid triaxial sample, the preparation process is more complex and the requirement is higher. Usually, most of traditional undisturbed solid triaxial test samples are undisturbed soil blocks taken back on site, an experimenter firstly adopts a soil divider to divide the undisturbed soil blocks, secondly, the divided soil samples are manufactured through a soil cutting disc of the undisturbed soil samples according to the design size of the triaxial test samples in the test scheme, and finally, redundant parts at two ends are cut off, so that the undisturbed solid soil samples can be obtained. In recent years, although many scholars adopt auxiliary equipment to prepare hollow undisturbed soil samples on the basis of the traditional preparation method, the difference of the auxiliary equipment is obvious, the success rate of the preparation of the hollow triaxial soil samples is seriously influenced, the application of the hollow cylindrical torsional shear triaxial test in the concrete geotechnical test is not facilitated, and the popularization in the geotechnical test for researching the complex stress state of soil is difficult. At the present stage, the dynamic and static hollow cylindrical torsional shear triaxial test technology is used as a main technical means for researching a complex stress path of a soil body, the requirements on the preparation process of a hollow cylindrical soil sample are higher, the precision requirements of dynamic and static hollow torsional shear on the soil sample in the test are difficult to meet by adopting a traditional sample preparation method, the research result is influenced, and the test efficiency is very low.
In summary, although researchers have prepared dynamic and static hollow cylindrical torsional shear triaxial soil samples by using some auxiliary sample preparation tools on the basis of the traditional solid triaxial samples, the methods have the following defects: 1. generally, the requirement on professional literacy of experimenters is high, the sample preparation process is very complex, the success rate of sample preparation is low, and the experimenters are difficult to widely use. 2. The operation steps in the sample preparation process are complicated and complicated, the disturbance to the soil sample is large, the fixed support structure is not used as a support, the soil sample is easily deformed under the action of uneven drilling torque, the two ends of the soil sample are flattened, the preparation error of the hollow triaxial soil sample is large, and the requirement of a soil test on the sample precision is difficult to meet. 3. Traditional undisturbed soil sample preparation instrument is closed solid cylinder structure mostly, and it is comparatively difficult to the drawing of patterns process after the preparation of hollow cylinder torsional shear triaxial soil sample is accomplished, hardly guarantees the preparation quality of hollow cylinder torsional shear triaxial soil sample.
Disclosure of Invention
Aiming at the problems in the prior art, the first technical problem to be solved by the invention is as follows: the device for preparing the undisturbed soil sample in the hollow cylinder torsional shear triaxial test is simple in structure and convenient to operate.
The second technical problem to be solved is: the preparation method of the undisturbed soil sample of the hollow cylinder torsional shear triaxial test is simple in sample preparation step operation and high in sample preparation precision and efficiency.
In order to solve the first technical problem, the invention adopts the following technical scheme: a preparation device for an undisturbed soil sample in a hollow cylindrical torsion-shear triaxial test comprises a dowel bar, an undisturbed soil sample fixer and a base; the left side and the right side of the base are respectively and fixedly connected with bracket supports, the top of each bracket support is provided with a detachable beam, the inner side of each bracket support is provided with a plurality of bracket supports, the bracket supports are arranged from top to bottom, and the height of the bracket supports on the two bracket supports in the vertical direction corresponds to each other one by one;
the outer side wall of the undisturbed soil sample fixer is provided with a plurality of steel sheet supports extending outwards, the undisturbed soil sample fixer is arranged between the two bracket supports, and the steel sheet supports are arranged on the bracket supports at corresponding heights and are matched and fixed; the center positions of the top and the bottom of the undisturbed soil sample fixer are provided with threaded holes; the bottom of the dowel bar sequentially penetrates through the center of the cross beam and threaded holes in the top of the undisturbed soil sample fixer to enter the undisturbed soil sample fixer, the dowel bar is rotatably connected with the cross beam, and a drill bit is detachably connected with the dowel bar; the dowel bar, the cross beam, the undisturbed soil sample fixer and the base are overlapped in axis.
As an improvement, the top of each bracket support is provided with a tenon along the front-back direction, the cross beam is provided with a groove along the front-back direction, and the tenon is in sliding fit with the corresponding groove.
As a refinement, the width of each bracket is 1/3 of the base.
As the improvement, every two bracket supports about bracket support inboard is equipped with, two steel sheet supports about having respectively on the left lateral wall of original state soil sample fixer and the right lateral wall, fix on setting up two bracket supports that two steel sheet supports of original state soil sample fixer lateral wall co-altitude correspond respectively.
As an improvement, a sleeve is sleeved on the outer side of the dowel bar and is in rotatable connection with the cross beam, and the sleeve is fixedly connected with the center of the cross beam.
As the improvement, the undisturbed soil sample fixer is of a cylindrical structure, and the undisturbed soil sample fixer is formed by two cylinder halves which divide the cylinder into two parts along the middle axial surface, and the two cylinder halves are connected into a whole through a hinge and a buckle.
As an improvement, a groove which is along the length direction and has a semicircular cross section is arranged on one vertical edge of two vertical edges of each cylinder half part, a semicircular tenon which is along the length direction and has a semicircular cross section is arranged on the other vertical edge, and the semicircular tenon on one cylinder half part is in sealing fit with the groove on the other cylinder half part.
As an improvement, the top and bottom ends of the undisturbed soil sample fixer are respectively provided with a circular steel sheet, the center of the circular steel sheet is provided with a threaded hole, the outer diameter of the circular steel sheet is consistent with that of the undisturbed soil sample fixer, and the inner diameter of the circular steel sheet is consistent with that of the drill bit.
In order to solve the second technical problem, the invention adopts the following technical scheme: the preparation method of the undisturbed soil sample for the hollow cylinder torsional shear triaxial test adopts the preparation device of the undisturbed soil sample for the hollow cylinder torsional shear triaxial test, and comprises the following steps:
the first step is as follows: taking soil, and axially processing the blank soil blocks retrieved on site on an undisturbed soil bracket to prepare a cylindrical undisturbed soil sample;
the second step is that: leveling, namely selecting an original state soil sample fixer with the same sample size, splicing two cylinder halves of the original state soil sample fixer together through a hinge, taking out the cylindrical original state soil sample obtained in the first step, putting the cylindrical original state soil sample into one cylinder half of the original state soil sample fixer, and fixing the two cylinder halves through a buckle 17 to finish sample loading;
slowly cutting the bottom of the cylindrical undisturbed soil sample by using a soil cutting knife to level, connecting the circular steel sheet with the corresponding threaded hole through a screw I after the bottom is leveled, and then vertically placing the undisturbed soil sample fixer between the two bracket supports;
then, leveling the top of the sample by using a soil cutting knife in the same way, then connecting the circular steel sheet at the top end with the corresponding threaded hole through a first screw, finishing leveling of the original soil sample, and performing the next step;
the third step: drilling: fixing the undisturbed soil sample fixer in the second step between the bracket supports through the steel sheet support and the corresponding bracket support 10;
testing whether the dowel bar can rotate clockwise or anticlockwise, then installing the dowel bar at the top end of the bracket support, and connecting and installing the bracket support on the cross beam through the groove and the corresponding tenon;
selecting a drill bit with the size consistent with the sample size required by the test scheme, connecting the drill bit to the bottom of the dowel bar, checking whether the axial lines of the drill bit, the undisturbed soil sample fixer and the cross beam are overlapped, and drilling after checking is finished;
the drill bit is in contact alignment with the upper end of the cylindrical undisturbed soil sample through the dowel bar, the dowel bar is manually rotated clockwise to slowly apply a rotating force to the drill bit, so that the drill bit enters the solid cylindrical undisturbed soil sample under the action of the force, the speed is slowed down again until the drilling is finished after the drill bit reaches a safe tunneling depth, and the dowel bar is slowly taken out;
the fourth step: sampling: and after the drilling in the third step is finished, detaching the cylindrical soil sample fixer, firstly detaching the circular steel sheets and the buckles at the top end and the bottom end of the cylindrical sample fixer, and taking out the hollow cylindrical triaxial sample.
Compared with the prior art, the invention has at least the following advantages:
1. the hollow cylinder torsional shear triaxial soil fixer and the force transmission device are firmly connected with the bracket with the base, so that the problem that three axes of a drill bit, a force transmission rod, the bracket and the fixer are difficult to align and coincide is effectively solved, the axis alignment of a drill hole is ensured, the height of the drill hole is consistent with that of the axis of the whole sample, and the preparation precision of the hollow cylinder soil sample is greatly improved according to the requirement of the No. 2 in the No. 19.3.1 of the latest national standard geotechnical test method Standard (GB/T50123 and 2019) on the undisturbed soil sample; the drill bit rotational speed of the preparation device can be effectively controlled, the hollow cylinder torsional shear triaxial soil sample can be directly taken out by opening the sample fixer after the soil sample is manufactured, compared with the existing sample preparation method, the problems that the undisturbed soil sample is difficult to sample and has large disturbance are solved, and the sample preparation device can greatly improve the preparation standard of the hollow cylinder torsional shear triaxial sample.
2. Compared with the existing complex operation preparation method, the preparation method provided by the invention has the advantages that the operation of geotechnical experimenters and scientific researches on the preparation process of the undisturbed soil sample of the hollow cylinder torsional shear triaxial test is simpler, the sample preparation process can be realized only by selecting the corresponding circular soil sample fixer according to the sample size of the test scheme and according to the preparation method provided by the invention, the undisturbed soil sample of the hollow cylinder torsional shear triaxial test meeting the test standard can be effectively and quickly obtained, the sample preparation efficiency of the experimenters and scientific researchers is greatly improved, and the preparation method can be effectively popularized in the indoor geotechnical test.
Drawings
FIG. 1 is a schematic sectional view of an undisturbed soil sample preparation device in a hollow cylindrical torsion-shear triaxial test.
Fig. 2 is a top plan view of an undisturbed soil sample preparation device for a hollow cylinder torsional-shear triaxial test.
Fig. 3 is a three-dimensional axial view of the undisturbed soil sample holder.
In the figure, a drill bit-1, a drill bit connecting part-2, a sleeve-3, a dowel bar-4, a cross beam-5, a tenon-6, a screw I-7, an undisturbed soil sample fixer-8, a bracket support-9, a bracket support-10, a circular steel sheet-11, a base-12, a steel sheet support-13, a screw II-14, a semicircular tenon-15, a hinge-16, a buckle-17, a cylinder half-18, a screw III-19 and an axis-20.
Detailed Description
The present invention is described in further detail below.
In the present invention, 'front', 'rear', 'left', 'right', 'up', 'down' all refer to the orientation in fig. 1, wherein 'front' refers to being out with respect to the paper in fig. 1 and 'rear' refers to being in fig. 1. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," "sleeved/connected," "connected," and the like are to be construed broadly, e.g., "connected," which may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Example 1: referring to fig. 1-3, a preparation device of undisturbed soil sample for hollow cylinder torsional shear triaxial test comprises a dowel bar 4, an undisturbed soil sample fixer 8 and a base 12.
The left side and the right side of the base 12 are respectively fixedly connected with a bracket support 9, the top of each bracket support 9 is provided with a detachable beam 5, in the specific implementation, the cross section of each beam 5 is rectangular, the inner side of each bracket support 9 is provided with a plurality of bracket supports 10, the bracket supports 10 are arranged from top to bottom, and the height of the bracket supports 10 on the two bracket supports 9 in the vertical direction corresponds to each other one by one; namely, one bracket support 9 is provided with a bracket support 10 at one height in the vertical direction, and the other bracket support 9 is also provided with a bracket support 10 at the same height in the vertical direction.
The outer side wall of the undisturbed soil sample fixer 8 is provided with a plurality of steel sheet supports 13 extending outwards, the undisturbed soil sample fixer 8 is arranged between the two bracket supports 9, and the steel sheet supports 13 are arranged on the bracket supports 10 at corresponding heights and are matched and fixed; the size of the undisturbed soil sample fixer 8 can be changed according to the soil sample size of the test scheme.
Threaded holes are formed in the center positions of the top and the bottom of the undisturbed soil sample fixer 8; the bottom of dowel bar 4 passes in proper order in crossbeam 5 center and the screw hole at 8 tops of undisturbed soil sample fixer get into undisturbed soil sample fixer 8 to dowel bar 4 and crossbeam 5 rotatable coupling, dowel bar 4 is installed on 5 axis of crossbeam and can clockwise or anticlockwise rotation, when adopting dowel bar 4 to apply the drilling moment of torsion, can be the size of artificial control drilling moment of torsion, reduce and disturb undisturbed soil sample at the drilling in-process. The dowel bar 4 is detachably connected with a drill bit 1; during concrete implementation, the top of drill bit 1 is connected with drill bit connecting portion 2, and drill bit connecting portion 2 can be integrated into one piece's structure with drill bit 1, has the screw thread on the drill bit connecting portion 2, and the bottom of dowel steel 4 is equipped with stealthy internal thread, screw-thread cooperation on stealthy internal thread and the drill bit connecting portion 2 is connected drill bit 1 and dowel steel 4, 1 lower extreme of drill bit has sharp curved cutting edge, and to a great extent has reduced the frictional force to the original state soil sample among the drilling process, has greatly improved drilling efficiency and has reduced the disturbance to the original state soil sample. Because drill bit 1 passes through threaded connection with dowel steel 4, consequently can be convenient change drill bit 1 as required to improve the suitability of hollow cylinder torsional shear triaxial test original state soil sample preparation facilities.
The dowel bar 4, the cross beam 5, the undisturbed soil sample fixer 8 and the base 12 are overlapped in axial line. Namely, the axes of the dowel bar 4, the cross beam 5, the undisturbed soil sample fixer 8 and the base 12 are coincided and coincided with the axis 20 of the whole preparation device, so that the preparation precision of the undisturbed soil sample is improved.
As a modification, the top of each bracket 9 is provided with a tenon 6 along the front-back direction, the cross beam 5 is provided with a groove along the front-back direction, and the tenon 6 is in sliding fit with the corresponding groove.
As a modification, the width of each bracket 9 is 1/3 of the base 12. Bracket 9 with base 12 adopts the welding, increases the stability of preparation equipment, just the width of bracket 9 does 2/3 of base 12 width.
As the improvement, every two bracket supports 10 about the bracket support 9 inboard is equipped with, two steel sheet supports 13 about having respectively on the left lateral wall of original state soil sample fixer 8 and the right lateral wall, two steel sheet supports 13 of the same height of original state soil sample fixer 8 lateral wall are fixed on setting up two bracket supports 10 that correspond respectively. During specific implementation, all have the screw hole on every steel sheet support 13, also have the screw hole on every bracket support 10, set up undisturbed soil sample fixer 8 between two bracket supports 9, steel sheet support 13 sets up bracket support 10 at corresponding height for screw hole on the steel sheet support 13 is coaxial with the screw hole on the bracket support 10 that corresponds, then two 14 screw holes on passing steel sheet support 13 simultaneously and the screw hole on the bracket support 10 that corresponds, thereby fix undisturbed soil sample fixer 8 between two bracket supports 9. In specific implementation, each steel sheet support 13 and each bracket support 10 are provided with two threads, so that each steel sheet support 13 and the corresponding bracket support 10 are fixed more stably. And the change sample size of convenient according to different dynamic and static hollow torsional shear triaxial test schemes, the flexibility is stronger.
As an improvement, a sleeve 3 is sleeved outside the dowel bar 4 and is in rotatable connection, and the sleeve 3 is fixedly connected with the center of the cross beam 5. The sleeve 3 is used for fixing the dowel bar 4, so that the drilling torque can be applied conveniently.
As an improvement, the undisturbed soil sample holder 8 is of a cylindrical structure, the undisturbed soil sample holder 8 is composed of two cylindrical half parts 18 dividing the cylinder into two parts along the central axis surface, and the two cylindrical half parts 18 are connected into a whole through hinges 16 and buckles 17.
Specifically, buckle 17 includes first sheet and second sheet, first sheet and second sheet respectively fixed mounting just are close to the edge on vertical limit in the outside of two cylinder halves 18, have a plurality of archs on the first sheet, the second sheet includes fixed part and connecting portion, the second sheet passes through the fixed part to be fixed in the outside of cylinder halves 18, fixed part and connecting portion rotatable coupling, a plurality of through-holes have on the connecting portion, the through-hole on the second sheet of fixing in the outside of one cylinder halves 18 is fixed with the protruding one-to-one cooperation on the first sheet of fixing in the outside of another cylinder halves 18.
In specific implementation, the two cylinder halves 18 are connected through the hinge 16 and the buckle 17, the edges of two vertical edges of the two cylinder halves 18 are respectively provided with a plurality of through holes, and the hinge 16, the first sheet member and the second sheet member can be fixed on the cylinder halves 18 through the third screw 19 and the corresponding threaded holes. The two cylinder halves 18 are made of steel materials, the steel sheet supports 13 are fixed on the outer side of each cylinder half 18 in a welding mode, the number of the steel sheet supports 13 is 4, the outer side of each cylinder half 18 is welded with two, and the two steel sheet supports 13 are distributed up and down. The connecting part of the steel sheet support 13 and the cylinder half part 18 is in a circular arc shape, and the inner diameter of the circular arc-shaped end part of the steel sheet support 13 is equal to the outer diameter of the cylinder half part 18.
As a modification, on two vertical sides of each cylinder half 18, one vertical side has a groove with a semicircular cross section along the length direction of the vertical side, the other vertical side has a semicircular tenon 15 with a semicircular cross section along the length direction of the vertical side, and the semicircular tenon 15 on one cylinder half 18 is in sealing fit with the groove on the other cylinder half 18. Namely, one side of the assembly gap of the undisturbed soil sample fixer 8 is provided with a semicircular bulge along the height direction of the fixer, and the other side is provided with a semicircular tenon 15 connected with a corresponding semicircular groove, so that the undisturbed soil sample fixer 8 forms a closed space.
As an improvement, the top and bottom ends of the undisturbed soil sample fixer 8 are respectively provided with a circular steel sheet 11, the center of the circular steel sheet 11 is provided with a threaded hole, the outer diameter of the circular steel sheet 11 is consistent with the outer diameter of the undisturbed soil sample fixer 8, and the inner diameter of the circular steel sheet 11 is consistent with the outer diameter of the drill bit 1. The undisturbed soil sample fixer 8 and the circular steel sheet 11 are connected with corresponding threaded holes through a first screw 7.
The internal diameter of original state soil sample fixer 8 is unanimous with the external diameter of cylindrical original state soil sample, and the highly unanimous of the height of original state soil sample fixer 8 and cylindrical original state soil sample, and the inner wall of original state soil sample fixer 8 just contacts with the outside of cylindrical original state soil sample, forms virtual horizontal restraint, can avoid making cylindrical original state soil sample to the drilling moment of torsion and take place the slope when drilling like this, improves the system appearance precision.
The dowel bar 4 can rotate clockwise or anticlockwise, the speed of the drill hole 1 and the torque of the drill hole can be controlled, and the disturbance of the drilling step on solid cylindrical undisturbed soil is reduced; the undisturbed soil sample fixer 8 is composed of two steel sheets with semicircular sections, after drilling is completed, the circular steel sheet 11 is detached, and the prepared dynamic hollow cylindrical triaxial sample can be taken out by opening the buckle 17; the height of the undisturbed soil sample fixer 8 is consistent with the height of a conventional movable hollow cylindrical triaxial sample, the flatness of the cylindrical undisturbed soil sample can be improved in the leveling process of the hollow cylindrical triaxial sample, the conventional preparation method of the undisturbed soil sample for the hollow torsional shear test is broken to a great extent through verification of the actual hollow cylindrical triaxial sample, and the problems of low preparation precision of the hollow cylindrical sample, difficulty in drilling, low sample preparation efficiency and large disturbance of the undisturbed soil sample are effectively solved.
Example 2: the preparation method of the undisturbed soil sample for the hollow cylinder torsional shear triaxial test adopts the preparation device of the undisturbed soil sample for the hollow cylinder torsional shear triaxial test, and the preparation method comprises the following steps:
the first step is as follows: taking soil, and axially processing the blank soil blocks taken back on site on an undisturbed soil support according to the undisturbed soil sample preparation standard in item 4.5 of GB/T50123-2019 of the latest national standard of geotechnical test methods, paying attention to the layering direction of the soil sample, so as to prepare a cylindrical undisturbed soil sample; disturbance to an undisturbed soil sample is probably reduced in the soil sampling engineering, and the process and the method for preparing the cylindrical undisturbed soil sample belong to the prior art.
The second step is that: leveling, namely selecting an undisturbed soil sample fixer 8 with the same sample size, splicing two cylinder halves 18 of the undisturbed soil sample fixer 8 together through a hinge 16, taking out the cylindrical undisturbed soil sample obtained in the first step, putting the cylindrical undisturbed soil sample into one cylinder half 18 of the undisturbed soil sample fixer 8, and fixing the two cylinder halves 18 through a buckle 17 to finish sample loading;
slowly cutting the bottom of the cylindrical undisturbed soil sample by using a soil cutting knife to level, connecting the circular steel sheet 11 with the corresponding threaded hole through the first screw 7 after the bottom is leveled, and vertically placing the undisturbed soil sample fixer 8 between the two bracket supports 9;
then, leveling the top of the sample by using a soil cutting knife in the same way, then connecting the circular steel sheet 11 at the top end with the corresponding threaded hole through the first screw 7, finishing leveling of the undisturbed soil sample, and performing the next step;
the third step: drilling: firstly, fixing the original soil sample fixer 8 between the bracket supports 9 through the steel sheet support 13 and the corresponding bracket support 10 in the second step;
secondly, testing whether the dowel bar 4 can rotate clockwise or anticlockwise, then installing the dowel bar 4 at the top end of the bracket support 9, and connecting and installing the bracket support 9 on the cross beam 5 through the groove and the corresponding tenon 6;
and thirdly, selecting a drill bit corresponding to the inner diameter of the hollow sample required in the test scheme, and installing = circular steel sheets 11 at the top and bottom ends of the undisturbed soil sample fixer 8 after the second step is completed.
Selecting a drill bit with the size consistent with the sample size required by the test scheme, connecting the drill bit 1 to the bottom of the dowel bar 4, connecting and fixing the drill bit through a threaded hole and the upper end of the drill bit, checking whether the axial lines of the drill bit 1, the undisturbed soil sample fixer 8 and the cross beam 5 are coincident or not, and drilling after checking is finished;
finally, the drill bit 1 is in contact alignment with the upper end of the cylindrical undisturbed soil sample through the dowel bar 4, the dowel bar 4 is manually rotated clockwise to slowly apply a rotating force to the drill bit 1, the drill bit 1 enters the solid cylindrical undisturbed soil sample under the action of the force, the speed is slowed down again until the drilling is finished after the drill bit 1 reaches a safe tunneling depth, and the dowel bar 4 is slowly taken out; and the disturbance to the cylindrical undisturbed soil sample is reduced. The safe depth is the design height of the sample minus the protective layer thickness of 2 cm.
The fourth step: sampling: and after the drilling in the third step is finished, the cylindrical soil sample fixer 8 is disassembled, the circular steel sheets 11 and the buckles 17 at the top end and the bottom end of the cylindrical sample fixer 8 are firstly disassembled, and the hollow cylindrical triaxial sample is taken out.
The preparation method is easy to operate, simultaneously, the original-state soil sample fixing devices, the circular steel sheets and the drill bits of different sizes can be replaced according to the design requirements of the test scheme, the flexibility is high, the sample preparation size range is wide, geotechnical test experimenters in the technical field can easily understand and operate, the preparation precision of the original-state soil sample is high, meanwhile, the disturbance to the soil particle structure of the cylindrical original-state soil sample is small, the success rate and the preparation speed of the preparation of the dynamic and static hollow cylindrical triaxial sample can be effectively guaranteed through the preparation device, and the operation difficulty of the hollow torsional shear triaxial test is greatly reduced.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.
Claims (9)
1. The utility model provides a hollow cylinder is turned round and is cut triaxial test original state soil sample preparation facilities which characterized in that: comprises a dowel bar (4), an undisturbed soil sample fixer (8) and a base (12);
the left side and the right side of the base (12) are respectively fixedly connected with a bracket support (9), the top of each bracket support (9) is provided with a detachable beam (5), the inner side of each bracket support (9) is provided with a plurality of bracket supports (10), the bracket supports (10) are arranged from top to bottom, and the height of the bracket supports (10) on the two bracket supports (9) in the vertical direction corresponds to one another;
the outer side wall of the undisturbed soil sample fixer (8) is provided with a plurality of steel sheet supports (13) extending outwards, the undisturbed soil sample fixer (8) is arranged between the two bracket supports (9), and the steel sheet supports (13) are arranged on the bracket supports (10) at corresponding heights and are matched and fixed;
the center positions of the top and the bottom of the undisturbed soil sample fixer (8) are provided with threaded holes;
the bottom of the dowel bar (4) sequentially penetrates through the center of the cross beam (5) and a threaded hole in the top of the undisturbed soil sample fixer (8) to enter the undisturbed soil sample fixer (8), the dowel bar (4) is rotatably connected with the cross beam (5), and the drill bit (1) is detachably connected with the dowel bar (4);
the axes of the dowel bar (4), the cross beam (5), the undisturbed soil sample fixer (8) and the base (12) are coincided.
2. The device for preparing the undisturbed soil sample for the hollow cylinder torsional-shear triaxial test of claim 1, is characterized in that: every the top of bracket support (9) has tenon (6) along fore-and-aft direction, have the recess along fore-and-aft direction on crossbeam (5), tenon (6) and the recess sliding fit that corresponds.
3. The device for preparing the undisturbed soil sample for the hollow cylinder torsional-shear triaxial test of claim 1, is characterized in that: the width of each bracket support (9) is 1/3 of the base (12).
4. The device for preparing the undisturbed soil sample for the hollow cylinder torsional-shear triaxial test of claim 1, is characterized in that: every two bracket supports (10) about bracket support (9) inboard is equipped with, two steel sheet supports (13) about having respectively on the left lateral wall of original state soil sample fixer (8) and the right lateral wall, and two steel sheet supports (13) of original state soil sample fixer (8) lateral wall co-altitude correspond respectively set up two bracket supports (10) go up to fix.
5. The device for preparing the undisturbed soil sample for the hollow cylinder torsional-shear triaxial test of claim 1, is characterized in that: the outer side of the dowel bar (4) is sleeved with a sleeve (3) which is rotatably connected, and the sleeve (3) is fixedly connected with the center of the cross beam (5).
6. The device for preparing the undisturbed soil sample for the hollow cylinder torsional-shear triaxial test of claim 1, is characterized in that: the undisturbed soil sample fixer (8) is of a cylindrical structure, the undisturbed soil sample fixer (8) is formed by two cylinder halves (18) dividing a cylinder into two parts along a middle axial surface, and the two cylinder halves (18) are connected into a whole through a hinge (16) and a buckle (17).
7. The device for preparing the undisturbed soil sample for the hollow cylinder torsional-shear triaxial test of claim 6, is characterized in that: and two vertical edges of each cylinder half part (18), one vertical edge is provided with a groove which is along the length direction of the cylinder half part and has a semicircular cross section, the other vertical edge is provided with a semicircular tenon (15) which is along the length direction of the cylinder half part and has a semicircular cross section, and the semicircular tenon (15) on one cylinder half part (18) is in sealing fit with the groove on the other cylinder half part (18).
8. The device for preparing the undisturbed soil sample for the hollow cylinder torsional-shear triaxial test of claim 7, is characterized in that: the top and bottom both ends of original state soil sample fixer (8) have set up ring steel sheet (11) respectively, the center of ring steel sheet (11) has set up the screw hole, ring steel sheet (11) external diameter with original state soil sample fixer (8) external diameter is unanimous, ring steel sheet (11) internal diameter with the external diameter of drill bit (1) is unanimous.
9. The preparation method of the undisturbed soil sample in the heart cylinder torsion-shear triaxial test is characterized by comprising the following steps of: the preparation device of the undisturbed soil sample for the hollow cylinder torsional-shear triaxial test of claim 8 is adopted, and the preparation method comprises the following steps:
the first step is as follows: taking soil, and axially processing the blank soil blocks retrieved on site on an undisturbed soil bracket to prepare a cylindrical undisturbed soil sample;
the second step is that: leveling, namely selecting an original state soil sample fixer (8) with the same sample size, splicing two cylinder halves (18) of the original state soil sample fixer (8) together through a hinge (16), taking out the cylindrical original state soil sample obtained in the first step, putting the cylindrical original state soil sample into one cylinder half (18) of the original state soil sample fixer (8), and fixing the two cylinder halves (18) through a buckle 17 to finish sample loading;
slowly cutting the bottom of the cylindrical undisturbed soil sample by using a soil cutting knife to level, connecting the circular steel sheet (11) with the corresponding threaded hole through a screw I (7) after the bottom is leveled, and vertically placing the undisturbed soil sample fixer (8) between the two bracket supports (9);
then, leveling the top of the sample by using a soil cutting knife in the same way, connecting the circular steel sheet (11) at the top end with the corresponding threaded hole through a screw I (7), finishing leveling of the original soil sample, and performing the next step;
the third step: drilling: fixing the undisturbed soil sample fixer (8) in the second step between the bracket supports (9) through the steel sheet supports (13) and the corresponding bracket supports (10);
testing whether the dowel bar (4) can rotate clockwise or anticlockwise, then installing the dowel bar (4) at the top end of the bracket support (9), and connecting and installing the bracket support (9) on the cross beam (5) through the groove and the corresponding tenon (6);
selecting a drill bit with the size consistent with the sample size required by the test scheme, connecting the drill bit (1) to the bottom of the dowel bar (4), checking whether the axial lines of the drill bit (1), the undisturbed soil sample fixer (8) and the cross beam (5) are overlapped, and drilling after checking is finished;
the drill bit (1) is in contact alignment with the upper end of the cylindrical undisturbed soil sample through the dowel steel (4), the dowel steel (4) is manually rotated clockwise to slowly apply a rotating force to the drill bit (1), so that the drill bit (1) enters the solid cylindrical undisturbed soil sample under the action of the force, the speed is slowed down again until the drilling is finished after the drill bit (1) reaches the safe tunneling depth, and the dowel steel (4) is slowly taken out;
the fourth step: sampling: and after the drilling in the third step is finished, the cylindrical soil sample fixer (8) is disassembled, the circular steel sheets (11) and the buckles (17) at the top end and the bottom end of the cylindrical sample fixer (8) are firstly disassembled, and the hollow cylindrical triaxial sample is taken out.
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