CN109959605B - Test method for detecting bonding strength of sprayed concrete and surrounding rock on site - Google Patents
Test method for detecting bonding strength of sprayed concrete and surrounding rock on site Download PDFInfo
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- CN109959605B CN109959605B CN201910354256.5A CN201910354256A CN109959605B CN 109959605 B CN109959605 B CN 109959605B CN 201910354256 A CN201910354256 A CN 201910354256A CN 109959605 B CN109959605 B CN 109959605B
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Abstract
The invention relates to a test method for detecting the bonding strength of sprayed concrete and surrounding rock on site, which comprises the following steps: 1) manufacturing an assembled steel die for molding a sprayed concrete test piece and a reaction frame for connecting the test piece and a dowel bar; 2) selecting a field test area; 3) manufacturing a sprayed concrete and surrounding rock bonding test piece on site at a test point, and manufacturing at least three test pieces; 4) naturally curing the test piece for 28 days; 5) respectively carrying out tensile bonding strength tests on the three test pieces; 6) and (6) judging the test result. The test device and the test method for detecting the bonding strength of the sprayed concrete and the surrounding rock on site overcome the problems of no fixed support on site and difficult erection of the dowel bar, and the test can be smoothly and effectively carried out. The test method is particularly suitable for vertical rock walls which cannot be supported.
Description
Technical Field
The invention belongs to the field of engineering construction, and particularly relates to a device and a method for testing the bonding strength of sprayed concrete and surrounding rock in field detection of water conservancy and hydropower, highway, railway engineering and the like.
Background
The sprayed concrete is a common construction method for tunnel and cavern support, the detection of the bonding strength of the sprayed concrete is an important means for detecting the quality of the sprayed concrete, and the test methods for the bonding strength of the sprayed concrete are correspondingly specified in the technical Specifications for anchor and spray support in the hydraulic and hydroelectric engineering (SL377-2007), the technical Specifications for rock-soil anchor rods and sprayed concrete support engineering (GB50086-2015) and the construction Specifications for anchor and spray support in the hydroelectric engineering (DL/T5181 and 2017), wherein the bonding strength test methods in the specifications are approximately the same, and after conclusion, the main detection methods are three, namely 1, a test piece reserved drawing method, 2, a drill core drawing method and 3, a large plate spray indoor splitting method. The goals of the test are mainly two-fold: 1. the stress is basically consistent with the bonding stress of the concrete sprayed on site, and 2, the test viscosity meets the requirement. However, the three methods at present have defects in the test piece forming, the test piece stress, the base surface requirement, the test instrument and the test method with different degrees of formation.
1) In-situ core drilling and drawing method
In the on-site core drilling and drawing method, when a core is drilled, the swing of a drilling machine disturbs and damages a concrete test piece; the loading is difficult to ensure not to be eccentric when the pull rod is buried in a drilled hole or the pull head is stuck by epoxy resin; stress concentration is easily caused by insufficient thickness of a sprayed layer, and the axial tension bonding strength obtained by the on-site core drilling and drawing method is small due to the factors, so that the detection result of the method cannot truly reflect the bonding condition of sprayed concrete and surrounding rock. In addition, when the integrity of surrounding rock randomly drilled on site is poor, core sample fracture is easy to occur during core drilling, and the success rate of the site core drilling method is low.
2) Spray large plate splitting method
The splitting and pulling test has a shearing phenomenon, so that the splitting and pulling bonding strength obtained by the large-plate-spraying splitting and pulling method is higher. In addition, the rock blocks are selected to be sprayed to form the large plate on the construction site, the actual condition of the site cannot be completely reflected, and the large plate comes in and goes out of the bonding condition of the actual sprayed concrete and surrounding rocks.
3) Reserved test piece drawing method
The sprayed concrete mixed with the accelerator can quickly develop the strength of the sprayed concrete, and the 50mm wide annular groove is difficult to dig, so that the reserved test piece can be damaged when labor cost is high. And the steel pull rod is pre-embedded firstly and then concrete is sprayed, and the steel pull rod is fixed on the rock surface, so that the steel pull rod is difficult to ensure that the steel pull rod is not eccentric when being loaded. When the sprayed layer is thick, the reserved test piece is heavy, the bonding strength of the concrete which is just sprayed and the surrounding rock is low, the test piece can not be hung, and the test result of the bonding strength can not be obtained due to test failure.
In conclusion, the three existing detection methods have some problems more or less, the test value deviates from the true value, the bonding strength test value cannot truly reflect the actual bonding strength condition, and the problems that the engineering quality cannot pass the acceptance according to the actual condition of the site due to the test error and the data is forged for passing the acceptance are caused.
And, the main difficulties of the field adhesion test are:
1 are mostly arranged on a vertical rock wall, and the test piece is difficult to fix.
2 there is no fixed support on site, the dowel bar is difficult to erect, and even if it is installed reluctantly, it will be deflected by the high-speed sprayed concrete when it is sprayed.
3, a test surface with better flatness is difficult to find on site, the flatness is poor after the spraying is finished, and the reaction frame is difficult to align when being erected.
4 the jack and the reaction frame are heavy, and the equipment needs to be supported by a plurality of people during field operation, so the labor intensity is high.
Disclosure of Invention
In order to overcome the problems, the invention provides a novel device and a novel method for testing the bonding strength of the sprayed concrete and the surrounding rock on site.
Specifically, the invention provides the following technical scheme:
the test method for detecting the bonding strength of the sprayed concrete and the surrounding rock on site comprises the following steps:
1) manufacturing an assembled steel die for molding a sprayed concrete test piece and a reaction frame for connecting the test piece and a dowel bar;
2) selecting a field test area: selecting a rock surface with the area of 500mm multiplied by 500mm as a test area; the range of 300mm multiplied by 300mm at the center of the test area is taken as a test point; removing dust, rock ballast and loose rock blocks on the surface of surrounding rock in a test area, so that the flatness of a test point is not more than 10mm, and the flatness outside the test point is not more than 30 mm;
3) manufacturing a sprayed concrete and surrounding rock bonding test piece on site at a test point, and manufacturing at least three test pieces;
4) naturally curing the test piece for 28 days;
5) respectively carrying out tensile bonding strength tests on the three test pieces;
6) and (3) judging test results:
(1) taking the average value of the tensile bonding strength tests of the three test pieces as the test result of the tensile bonding strength;
(2) when the difference between the strength test value of one test piece and the average value is more than 20 percent of the average value, taking the strength average value of the rest two test pieces as a test result;
(3) taking the arithmetic mean value of the bonding strength test values of the three test pieces as a test result, when the difference between the bonding strength test values of the two test pieces and the mean value is more than 20 percent of the mean value, adding three test pieces, and combining the test results of the six test pieces for calculation; and when the difference between the bonding strength test values of the six test pieces and the average value is not more than 20 percent of the average value, the two test values are rejected, the average value of the strength of the rest test pieces is used as a test result, and when the difference between the bonding strength test values of the six test pieces and the average value is more than 20 percent of the average value, the test is invalid, the reason is analyzed, and the test part is reselected for redoing the test.
In some preferred embodiments, the assembled steel die comprises two semi-cylindrical templates and a sleeve, and the outer wall of the sleeve is connected with a cross-shaped symmetrical wing plate; the two semi-cylindrical templates are spliced into a cylindrical steel mold, the outer sides of the cross-shaped symmetrical wing plates are welded with connecting plates with screw holes, and the cross-shaped symmetrical wing plates are connected to the inner side walls of the cylindrical templates through the connecting plates; the semi-cylindrical template is provided with a mounting hole corresponding to the connecting plate.
In some preferred embodiments, the reaction frame comprises a bottom plate, a bearing plate, a plurality of screw rods for connecting the bottom plate and the bearing plate, and an upper nut and a lower nut sleeved on the screw rods and respectively positioned above and below the bearing plate.
In some preferred embodiments, the step 3) of preparing the test piece specifically includes the following steps:
(1) aligning and folding the two semi-cylindrical templates to form a cylindrical template, then placing the sleeve with the cross wing plate in the cylindrical steel mold, butting the threaded hole of the connecting plate with the mounting hole on the cylindrical steel mold, and locking the mounting hole and the threaded hole by using a countersunk head screw to complete the assembly of the assembled steel mold;
(2) sticking a circle of extruded sheet or pearl wool board with the thickness of 20mm and other isolating materials on the outer side of the cylindrical template;
(3) filling and leveling the pits on the surface of the surrounding rock of the test point;
(4) respectively drilling an expansion bolt at two ends of the central axis of the test point, fixing the assembled steel die at the test point position by using a steel wire, clamping the upper surface of the assembled steel die by using the steel wire, and tightly drawing the steel wire to ensure that the steel die cannot be loosened;
(5) screwing a choke plug screw in the inserting groove of the sleeve to prevent the sprayed concrete from entering the sleeve;
(6) and (3) spraying concrete in the assembled steel die, stopping spraying when the spraying thickness reaches the outer opening of the assembled steel die, and scraping the concrete in the test area by using a scraping rule, wherein the thickness is leveled with the outer opening of the assembled steel die.
In some preferred embodiments, the tensile bond strength test in step 5) specifically comprises the following steps:
(1) after the maintenance of the test piece is finished, excavating an isolation material adhered to the assembled steel die, cutting off a steel wire for fixing the assembled steel die, and screwing out a choke plug screw in the connecting slot;
(2) inserting one end of a dowel bar into the inserting slot of the sleeve for fixing;
(3) punching a hole on the sprayed concrete surface at a position right above the dowel bar according to the distance from the circle center of the base plate of the reaction frame to the hanging hole, inserting a steel bar, penetrating the base plate of the reaction frame through the other end of the dowel bar and hanging the hanging hole of the base plate on the steel bar; installing four screw rods on the bottom plate, sleeving lower nuts on the screw rods, enabling the pressure bearing plate to penetrate through the other end of the dowel bar, sleeving the pressure bearing plate on the four screw rods, and finally sleeving upper nuts on the screw rods; lightly pressing the reaction frame to make the bottom plate of the reaction frame tightly attached to the concrete surface in the assembled template, leaning against the bearing plate by a T-square, adjusting the upper and lower nuts of the screw rod to make the bearing plate perpendicular to the dowel bar, and then screwing the upper and lower nuts;
(4) installing a jack, enabling the other end of the dowel bar to penetrate through a center hole of the jack, slightly pushing the jack, enabling the bottom of the jack to be located in a groove on the bearing plate, supporting the jack by using a lute support, and enabling the dowel bar to be located in the center of the center hole of the jack;
(5) sleeving a hollow spherical hinge and a nut on the other end of the dowel bar, and screwing the nut to ensure that the reaction frame, the jack and the spherical hinge are fixed on the dowel bar in sequence;
(6) and slowly applying tension to the dowel bar at the speed of 10kN/min until the test piece in the steel die is damaged, and recording the damage load.
In some preferred embodiments, in order to ensure safety and prevent the object from falling to hurt people after the test piece is damaged, the steel bar and the dowel bar of the hanging hole are connected through the steel rope.
On the other hand, the invention also provides a device for testing the bonding strength between the sprayed concrete and the surrounding rock on site, which comprises an assembled steel die, a reaction frame, a dowel bar and a jack, wherein one end of the dowel bar is fixed in the assembled steel die, and the centers of the reaction frame and the jack penetrate through the other end of the dowel bar and are sequentially sleeved on the dowel bar.
In some preferred embodiments, the device further comprises a ball hinge and a nut which are sleeved on the dowel bar; the reaction frame and the jack are fixedly locked on the dowel bar through the spherical hinge and the nut.
In some preferred embodiments, the assembled steel die comprises two semi-cylindrical templates and a sleeve, and the outer wall of the sleeve is connected with a cross-shaped symmetrical wing plate; the two semi-cylindrical templates are spliced into a cylindrical steel mold, the outer sides of the cross-shaped symmetrical wing plates are welded with connecting plates with screw holes, and the cross-shaped symmetrical wing plates are connected to the inner side walls of the cylindrical templates through the connecting plates; the semi-cylindrical template is provided with a mounting hole corresponding to the connecting plate.
In some preferred embodiments, after the semi-cylindrical templates are spliced into the cylindrical steel mold, the sleeve with the cross wing plate is placed in the cylindrical steel mold, the threaded hole of the connecting plate is butted with the mounting hole in the cylindrical steel mold, and the mounting hole and the threaded hole are locked by using a countersunk head screw.
In a specific implementation mode, the spliced cylindrical steel die is fixed by locking the mounting hole and the screw hole through a countersunk screw.
In some preferred embodiments, the sleeve has an insertion slot therein, and one end of the dowel bar is inserted into the insertion slot and fixedly connected with the sleeve. In a specific embodiment, an internal thread is arranged in the inserting groove; one end of the dowel bar is of a screw tooth structure; the dowel bar is fixed in the inserting slot through the occlusion connection of the internal thread and the screw teeth.
In some preferred embodiments, the reaction frame comprises a bottom plate, a bearing plate, a plurality of screw rods for connecting the bottom plate and the bearing plate, and an upper nut and a lower nut sleeved on the screw rods and respectively positioned above and below the bearing plate.
In some preferred embodiments, the bottom plate and the bearing plate are of circular ring structures; the center of the circular ring of the bottom plate and the bearing plate passes through the dowel bar.
In some preferred embodiments, a groove is arranged at the center of the bearing plate, and the diameter of the groove is larger than the inner diameter of the circular ring of the bearing plate; the bottom of the jack is positioned in the groove of the bearing plate to fix the jack and the reaction frame.
Advantageous effects
The test device and the test method for detecting the bonding strength of the sprayed concrete and the surrounding rock on site overcome the problems of no fixed support on site and difficult erection of the dowel bar, and the test can be smoothly and effectively carried out. The test method is particularly suitable for vertical rock walls which cannot be supported. And moreover, the assembly steel die is suitable for on-site assembly and is convenient to operate. And moreover, the dowel bar can be perpendicular to the rock and concrete test piece through the steel die, and the success and the high efficiency of a field test bonding strength test are ensured. The reaction frame can enable the jack and the dowel bar which are arranged on the reaction frame to be stressed coaxially, so that the stress of a bonding strength test is ensured not to deviate; and the reaction frame can be split into a plurality of parts, thereby being convenient for carrying and installation. The reaction frame and the steel die structure arranged in the invention enable the dowel bar to be positioned at the center of the test piece and to be vertical to the bonding surface, and the dowel bar and the bonding test piece conduct forward force to ensure the stress forward direction of the bonding test piece, thereby ensuring the success rate and the accuracy of the bonding strength test.
Drawings
FIG. 1 is a schematic view of a cylindrical steel die of the present invention.
Fig. 2 is a schematic view of a sleeve with a cross wing of the present invention.
Fig. 3 is a schematic cross-sectional view of a sleeve B-B with a cruciform flap of the present invention.
Fig. 4 is a schematic structural view of the assembled steel die of the present invention.
FIG. 5 is a schematic view of the A-A section of the assembled steel die of the present invention.
Fig. 6 is a top view of the steel form fixed to the surrounding rock (experimental surface).
Fig. 7 is a schematic structural diagram of the reaction frame of the present invention.
Fig. 8 is a schematic view of a base of the present invention.
Fig. 9 is a side view of the base of the present invention.
Fig. 10 is a schematic view of the force bearing plate of the invention.
Fig. 11 is a side view of the force bearing plate of the present invention.
FIG. 12 is a schematic view of the steel form of the present invention being fixed to a surrounding rock.
Fig. 13 is a schematic diagram of the device for testing the bonding strength between the sprayed concrete and the surrounding rock in the field test after the steel mould and the surrounding rock are fixed and then the concrete is sprayed.
FIG. 14 is a schematic diagram of the device for testing the bonding strength of the sprayed concrete and the surrounding rock on site according to the invention, after the steel die is separated from the sprayed concrete and the bulkhead bolt is unscrewed.
FIG. 15 is a schematic view of the connection between a steel mold and a dowel bar of the device for testing the bonding strength between shotcrete and surrounding rock in situ.
FIG. 16 is a schematic view of the apparatus for testing the bonding strength between shotcrete and surrounding rock in situ according to the present invention.
Fig. 17A and 17B are schematic views of the ball-hinge upper seat.
Fig. 18A and 18B are schematic views of a ball-and-socket joint lower seat.
Reference numerals
The concrete-filled steel formwork comprises a spliced steel die 200, a semi-cylindrical formwork 210, a formwork one-side edge 211, a formwork other-side edge 212, a wire groove 213, a sleeve 220, a cross symmetrical wing plate 221, a plug groove 222, an isolation material 240, an expansion bolt 270, a steel wire 260, a choke plug screw 280, a reaction frame 100, a base 110, a plug part 111, a base hanging part 112, a hanging hole 113, a bearing plate 120, a groove 121, a through hole 122, a stiffening rib 123, a screw 130, concrete 300, a concrete specimen 320, a concrete and concrete specimen space 310, a surrounding rock 400, a dowel bar 500, a jack 600, a ball hinge 700, a ball hinge upper seat 710, a ball hinge lower seat 720, a nut 900
Detailed Description
The present invention will be further described with reference to the structures or terms used herein. In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is not excluded that the invention can also be implemented in other embodiments and that the structure of the invention can be varied without departing from the scope of use of the invention.
As shown in fig. 1 to 5, the splicing steel form 200 for testing the bonding strength of shotcrete and rock on site according to the present invention includes two semi-cylindrical forms 210, and the two semi-cylindrical forms 210 enclose to form a cylindrical steel form. The cylindrical steel die is used for receiving sprayed concrete and forming a test piece after curing.
The splicing steel die 200 further includes a sleeve 220, the sleeve 220 is used for receiving the dowel, so that a receiving slot 222 is formed in the sleeve 220, and an internal thread is formed in the receiving slot for connecting the dowel of the thread. In particular embodiments. The bottom of the sleeve 220 has an enlarged head 226 of 50-56mm diameter, specifically 52 mm. The diameter of the sleeve is 40mm, the diameter of the plug slot is 25mm, and the depth is 58 mm.
A cross-shaped symmetrical wing plate 221 is connected to the outer wall of the sleeve 220, and the cross-shaped symmetrical wing plate 221 is used for fixedly connecting the sleeve 220 with the cylindrical steel die. In a specific embodiment, two semi-cylindrical templates 210 are butted and assembled to form an outer wall of the steel mold 200, the mounting holes 211 of the outer wall 200 are aligned with the screw holes 224 of the connecting plates 223 at the ends of the cross wing plates 221, and the assembly is completed by screwing the countersunk screws 225.
In the invention, the outer wall of the steel mould is provided with the mounting hole 211 which can be fixed with the connecting plate 223 of the wing plate 221, once the assembly is completed, the stress direction of the pull rod is fixed, and the interference of the impact force of the sprayed concrete in the construction process is avoided.
In some embodiments, the spliced cylindrical template 200 has a diameter of Φ 200 mm. The height of the cylindrical die plate 200 is between 70-100 mm.
When in use, the two semi-cylindrical templates 210 are correspondingly spliced to form the cylindrical template 200. The cross-shaped symmetrical wing plate 221 is placed in the cylindrical template 200, the screw holes 224 of the connecting plates 223 of the wing plate 221 are aligned with the mounting holes 211 of the cylindrical template 200, the countersunk screws 226 are screwed on the screw holes to complete the assembly, when the cross-shaped symmetrical wing plate is used for fixing on a test surface, as shown in fig. 6, two expansion bolts 270 are installed on two sides of the steel die 200, the expansion bolts 270 are connected by steel wires 260, and the steel die 200 is pressed tightly, so that the steel die 200 can be fixed on the test surface.
As shown in fig. 7 to 11, the reaction frame 100 for testing the bonding strength of shotcrete and rock in situ according to the present invention includes a base plate 110 and a force-bearing plate 120, and the base plate 110 and the force-bearing plate 120 are connected by a screw 130 and a nut. Wherein, the screw rods 130 are multiple and are connected at the edges of the bottom plate 110 and the bearing plate 120. Specifically, the base plate 110 has a plurality of screw bases 111 for inserting and fixing screws, and the screw bases 111 are uniformly distributed around the base plate 110. In one embodiment, there are 4 screws and 4 screw bases corresponding to the screws. The screw 130 is inserted into the screw base 111 and fixed. A plurality of through holes 122 sleeved with screws are uniformly distributed on the periphery of the bearing plate 120, wherein the positions of the through holes 122 correspond to the positions of the screw bases 111 on the base plate, so as to ensure that the screws 130 are in a vertical state after being connected with the base plate 110 and the bearing plate 120. In a specific embodiment, the number of through holes is 4. The screw 130 is sleeved with the lower nut 140, then sleeved with the bearing plate 120 through the through hole 122, and finally sleeved with the screw 130 and the nut 150. Thus, by adjusting the position of the upper nut 140/150 and the lower nut 140/150 on each screw 130, the upper and the lower positions of the bearing plate 120 on the screws 130 can be adjusted, and the angle of the bearing plate 120 relative to the vertically erected screws 130 can be slightly adjusted, so that the jack and the dowel bar on the bearing plate 120 can be stressed coaxially.
In some embodiments, the bottom plate 110 is a circular ring structure, and the screw bases 111 are uniformly located on the circular ring. Wherein, the screw base 111 has a recess in the middle for receiving and fixing the bottom of the screw 130.
In one embodiment of the present invention, the number of the screws 130, the screw bases 111 and the through holes 122 is 4, and these components are connected in a one-to-one correspondence. In some embodiments, the screw 130 is of dimensions Φ 25 × 140 mm.
The bearing plate 120 is also of a circular ring structure. The outer diameters of the bottom plate 110 and the circular ring of the bearing plate 120 are the same, and the inner diameter of the circular ring of the bearing plate 120 is smaller than the inner diameter of the circular ring of the bottom plate 110. In some specific embodiments, the outer diameter of the circular rings of the bottom plate 110 and the bearing plate 120 is phi 320 mm; the inner diameter of the circular ring of the bearing plate 120 is phi 50mm, and the inner diameter of the circular ring of the bottom plate 110 is phi 260 mm. The through holes 122 are uniformly distributed at the edge of the annular bearing plate 120.
The center of the bearing plate 120 is provided with a groove 121, and the diameter of the groove 121 is larger than the inner diameter of the circular ring of the bearing plate 120. In one embodiment, the groove 121 has a diameter of Φ 100 mm.
In a specific embodiment, a plurality of stiffening ribs 123 are uniformly fixed on the upper surface of the bearing plate 120. The stiffener 123 is located between the groove 121 and the through hole 122.
Also provided on the base plate 110 is an ear plate 112 projecting from the edge of the base plate, and provided in the middle thereof with a hanging hole 113, the hanging hole 112 being used for hanging on a concrete sample during the initial process of mounting the reaction frame 100 during the bonding strength test.
When the device is used, a hole with the depth of 150mm and the diameter phi of 20 is drilled on the surface of a concrete sample, a steel bar is inserted, a hanging hole 113 of a base plate of a reaction frame is hung on the steel bar, four pressure-bearing screw rods 130 are installed on the base plate 110, a pressure-bearing plate 120 is sleeved on the base plate, the reaction frame 100 is lightly pressed by hand to be tightly attached to the surface of concrete, a T-square is used for leaning against the pressure-bearing plate 120, nuts 140 and 150 of the pressure-bearing screw rods are adjusted, and the nut is screwed after the pressure-bearing plate 120 is perpendicular to a dowel steel. And (3) mounting the jack, enabling the dowel bar to penetrate through the center hole of the jack, slightly pushing the jack, enabling the bottom of the jack to fall into the circular groove 121 on the bearing plate, supporting the jack by using a lute support, and enabling the dowel bar to be located in the circle center of the center hole of the jack.
The device for testing the bonding strength between the sprayed concrete and the surrounding rock on site, disclosed by the invention, comprises a dowel bar 500 and a jack 600 besides the assembled template 200 and the reaction frame 100, and the dowel bar 500 is used for transmitting force to the test piece 320, so that one end of the dowel bar 500 is inserted into the assembled steel die 200 and is integrated with the test piece 320 in the steel die 200, as shown in fig. 12-16. Specifically, one end of the dowel bar is inserted into the insertion slot 222 of the sleeve of the splicing steel die and fixed. In some embodiments, the socket 222 is internally threaded, and the dowel 500 has threads at one end, and the dowel 500 is inserted into the socket 222, so that the dowel 500 is fixed to the sleeve 220 by the engagement of the threads and the internal threads. The bottom plate 110 and the force-bearing plate 120 of the reaction frame 100 then pass through the dowel 500 through the center of the ring. The jack 600 is sleeved on the dowel 500 and is fixedly connected with the reaction frame 100. Specifically, after the other end of the dowel bar 500 passes through the center hole of the jack 600, the bottom of the jack 600 falls into the groove 121 of the bearing plate, the jack 600 is supported by a lute support, and the dowel bar 500 is adjusted to enable the dowel bar 500 to be located at the center of the center hole of the jack 600. If necessary, the upper and lower nuts 140, 150 on each screw 130 are adjusted, the upper and lower positions of the bearing plate 120 on the screw 130 can be adjusted, and the angle of the bearing plate 120 relative to the vertically erected screw 130 can be slightly adjusted, so that the jack 600 on the bearing plate 120 and the dowel 500 can be stressed coaxially. The dowel 500 is further sleeved with a ball hinge 700 and a nut 900, wherein the ball hinge 700 is placed at the other end of the jack 600, the outermost nut 900 is screwed, and the dowel 500 and all components connected to the dowel are locked. In some embodiments, the ball hinge 700 is two-part: the spherical hinge upper seat 710 and the spherical hinge lower seat 720 are respectively shown in fig. 17A, 17B, 18A and 18B, and the spherical hinge upper seat falls into the spherical hinge lower seat cambered surface and can freely rotate, so that the dowel bar is automatically aligned with the pulling force of the jack.
In the present invention, the bond strength test is performed by using a device for testing the bond strength between shotcrete and surrounding rock on site, and the specific operation method is described below with reference to fig. 1 to 18 as follows:
1. the device manufacturing in the test is prepared, and comprises the steps of manufacturing an assembled steel die 200 for injection concrete sample molding and manufacturing a reaction frame 100 for connecting a sample 320 and a dowel bar 500.
2. Selecting a field test area, and selecting a rock surface with the area of 500mm multiplied by 500mm as a test area; the test point 400 is set in the range of 300mm × 300mm at the center of the test area; and removing dust, rock ballast and loose rock blocks on the surface of the surrounding rock in the test area, so that the flatness of a test point is not more than 10mm, and the flatness outside the test point is not more than 30 mm.
3. The concrete shotcrete and surrounding rock bonding test piece 320 is manufactured on site at the test point 400, and the concrete operation is as follows:
(1) aligning and folding the two semi-cylindrical templates 210 to form a cylindrical template 200, then placing the sleeve 220 with the cross wing plate 221 in the cylindrical steel mold 200, butting the threaded hole 224 of the connecting plate 223 with the mounting hole 211 on the cylindrical steel mold, and locking the mounting hole 211 and the threaded hole 224 by using a countersunk head screw 226 to complete the assembly of the assembled steel mold 200;
(2) a circle of isolation material 240 such as an extruded sheet or a pearl wool sheet with the thickness of 20mm is stuck on the outer side of the cylindrical template 200;
(3) filling and leveling the pits on the surface of the surrounding rock of the test point; because the surface of the surrounding rock fluctuates after blasting operation, filling the pits can enable the sprayed concrete surface to be smooth, and the installation of the reaction frame is not influenced;
(4) respectively drilling an expansion bolt 270 at two ends of the central axis of the test point, fixing the assembled steel die 200 at the test point 400 by using a steel wire 260 as shown in fig. 7, clamping the upper surface of the assembled steel die 200 by using the steel wire 260, and tightly drawing the steel wire 260 to ensure that the steel die 200 cannot loosen;
(5) screwing a bulkhead screw 280 into the socket 222 of the sleeve 220 to prevent the shotcrete from entering the sleeve 220, as shown in fig. 12;
(6) and (3) spraying concrete in the assembled steel die 200, stopping spraying when the spraying thickness reaches the outer opening of the assembled steel die 200, and scraping the concrete 300 in the test area by using a scraper in time, wherein the thickness is flush with the outer opening of the steel die 200, as shown in fig. 13.
4. Repeating the step 3 twice, and then manufacturing two test pieces 320.
5. And naturally curing the test piece for 28 days.
6. The tensile bond strength test is performed on the three test pieces 320 respectively, and the specific operation method comprises the following steps:
(1) after the test piece 320 is cured, the isolating material 240 adhered to the assembled steel die 200 is dug to form a concrete and concrete test piece space 310, so that the test piece 320 is separated from the rest of the concrete 300 to form an independent test piece 320; the steel wire 260 of the fixed assembly steel die 200 is cut off and the bulkhead screw 280 in the socket 222 is screwed out, as shown in fig. 14;
(2) inserting one end of the dowel 500 into the socket 222 of the sleeve to be fixed, as shown in fig. 15;
(3) drilling a hole (not shown) in the surface of the sprayed concrete 300 at a position right above the dowel bar 500 according to the distance from the circle center of the reaction frame bottom plate 110 to the hanging hole 113, inserting a steel bar, penetrating the reaction frame bottom plate 110 through the other end of the dowel bar 500 and hanging the hanging hole 113 of the bottom plate on the steel bar; installing four screw rods 130 on the bottom plate 110, sleeving lower nuts 140 on the screw rods 130, penetrating the pressure bearing plate 120 through the other end of the dowel bar 500, sleeving the pressure bearing plate 120 on the four screw rods 130, and finally sleeving upper nuts 150 on the screw rods 130; lightly pressing the reaction frame 100 to make the bottom plate 110 of the reaction frame tightly adhere to the concrete 300 and the surface of the test piece 320, leaning against the bearing plate 120 by a T-square, adjusting the upper and lower nuts 140, 150 of the bearing screw 130 to make the bearing plate 120 and the dowel 500 vertical, and then screwing the upper and lower nuts 140, 150;
(4) installing the jack 600, enabling the other end of the dowel bar 500 to penetrate through a center hole of the jack 600, slightly pushing the jack 600 in, enabling the bottom of the jack 600 to be located in the groove 121 in the pressure bearing plate, supporting the jack 600 through a lute support, and adjusting to enable the dowel bar 500 to be located in the center of the center hole of the jack 600;
(5) sleeving a hollow spherical hinge 700 and a nut 900 on the dowel 500, and screwing down the nut 900 to fix the reaction frame 100, the jack 600 and the spherical hinge 700 on the dowel 500; FIG. 16;
(6) the steel bars of the hanging holes and the dowel bar 500 are connected through steel ropes (not shown in the figure), so that the object is prevented from falling to hurt people after the test piece 320 is damaged;
(7) a tensile force is slowly applied to the dowel bar 500 at a rate of 10kN/min until the test piece 320 in the steel mold 200 connected to the dowel bar 500 is broken, and the breaking load is recorded.
7. And (3) judging test results:
(1) the average value of the tensile bond strength tests of the three test pieces 320 is taken as the test result of the tensile bond strength;
(2) when the difference between the strength test value and the average value of one test piece 320 is more than 20 percent of the average value, taking the strength average value of the rest two test pieces as a test result;
(3) taking the arithmetic mean value of the bonding strength test values of the three test pieces as a test result, when the difference between the strength value of the bonding strength test values of the two test pieces and the mean value is more than 20 percent of the mean value, adding three test pieces, and combining the test results of the six test pieces for calculation; and when the difference between the strength value of the bonding strength test value of not more than three test pieces and the average value is more than 20 percent of the average value, the two test pieces are rejected, the average value of the strength of the rest test pieces is used as a test result, otherwise, when the difference between the bonding strength test value of the six test pieces and the average value is more than 20 percent of the average value, the test is invalid, the reason is analyzed, and the test part is selected again to be subjected to the test.
8. The test was completed.
Claims (4)
1. The test method for detecting the bonding strength of the sprayed concrete and the surrounding rock on site is characterized by comprising the following steps of:
1) manufacturing an assembled steel die for molding a sprayed concrete test piece and a reaction frame for connecting the test piece and a dowel bar; the assembled steel die comprises two semi-cylindrical templates and a sleeve, and the outer wall of the sleeve is connected with cross-shaped symmetrical wing plates; the two semi-cylindrical templates are spliced into a cylindrical steel mold, the outer sides of the cross-shaped symmetrical wing plates are welded with connecting plates with screw holes, and the cross-shaped symmetrical wing plates are connected to the inner side walls of the semi-cylindrical templates through the connecting plates; the semi-cylindrical template is provided with a mounting hole corresponding to the connecting plate; the sleeve is internally provided with a socket, and internal threads are arranged in the socket; the bottom of the sleeve is provided with an expanding head; the reaction frame comprises a bottom plate, a bearing plate, a plurality of screw rods for connecting the bottom plate and the bearing plate, and an upper nut and a lower nut which are sleeved on the screw rods and are respectively positioned above and below the bearing plate; the bottom plate and the bearing plate are of circular structures; a groove is arranged at the center of the bearing plate, and the diameter of the groove is larger than the inner diameter of the circular ring of the bearing plate;
2) selecting a field test area: selecting a rock surface with the area of 500mm multiplied by 500mm as a test area; the range of 300mm multiplied by 300mm at the center of the test area is taken as a test point; removing dust, rock ballast and loose rock blocks on the surface of surrounding rock in a test area, so that the flatness of a test point is not more than 10mm, and the flatness outside the test point is not more than 30 mm;
3) manufacturing a sprayed concrete and surrounding rock bonding test piece on site at a test point, and manufacturing at least three test pieces; the manufacturing method of the test piece specifically comprises the following steps:
(1) aligning and folding the two semi-cylindrical templates to form a cylindrical steel die, then placing the sleeve with the cross wing plate in the cylindrical steel die, butting the threaded hole of the connecting plate with the mounting hole on the cylindrical steel die, and locking the mounting hole and the threaded hole by using a countersunk head screw to complete the assembly of the assembled steel die;
sticking a circle of extruded sheet or pearl wool board with the thickness of 20mm on the outer side of the cylindrical steel mould;
(3) filling and leveling the pits on the surface of the surrounding rock of the test point;
(4) respectively drilling an expansion bolt at two ends of the central axis of the test point, fixing the assembled steel die at the test point position by using a steel wire, clamping the upper surface of the assembled steel die by using the steel wire, and tightly drawing the steel wire to ensure that the steel die cannot be loosened;
(5) screwing a choke plug screw in the inserting groove of the sleeve to prevent the sprayed concrete from entering the sleeve;
(6) spraying concrete in the assembled steel die, stopping spraying when the spraying thickness reaches the outer opening of the assembled steel die, and scraping the concrete in the test area by using a scraping rule in time, wherein the thickness is flush with the outer opening of the assembled steel die;
4) naturally curing the test piece for 28 days;
5) respectively carrying out tensile bonding strength tests on the three test pieces; the tensile bond strength test specifically comprises the following steps:
(1) after the maintenance of the test piece is finished, excavating an isolation material adhered to the assembled steel die, cutting off a steel wire for fixing the assembled steel die, and screwing out a choke plug screw in the connecting slot;
(2) inserting one end of a dowel bar into the inserting slot of the sleeve for fixing;
(3) punching a hole on the sprayed concrete surface at a position right above the dowel bar according to the distance from the circle center of the base plate of the reaction frame to the hanging hole, inserting a steel bar, penetrating the base plate of the reaction frame through the other end of the dowel bar and hanging the hanging hole of the base plate on the steel bar; installing four screw rods on the bottom plate, sleeving lower nuts on the screw rods, enabling the pressure bearing plate to penetrate through the other end of the dowel bar, sleeving the pressure bearing plate on the four screw rods, and finally sleeving upper nuts on the screw rods; lightly pressing the reaction frame to make the bottom plate of the reaction frame tightly attached to the concrete surface in the assembled template, leaning against the bearing plate by a T-square, adjusting the upper and lower nuts of the screw rod to make the bearing plate perpendicular to the dowel bar, and then screwing the upper and lower nuts;
(4) installing a jack, enabling the other end of the dowel bar to penetrate through a center hole of the jack, slightly pushing the jack, enabling the bottom of the jack to be located in a groove on the bearing plate, supporting the jack by using a lute support, and enabling the dowel bar to be located in the center of the center hole of the jack;
(5) sleeving a hollow spherical hinge, a spherical hinge pad and a nut on the other end of the dowel bar, and screwing the nut to ensure that the reaction frame, the jack and the spherical hinge are fixed on the dowel bar in sequence;
(6) slowly applying a pulling force to the dowel bar at the speed of 10kN/min until the test piece in the steel die is damaged, and recording the damage load;
6) and (3) judging test results:
(1) taking the average value of the tensile bonding strength tests of the three test pieces as the test result of the tensile bonding strength;
(2) when the difference between the strength test value of one test piece and the average value is more than 20 percent of the average value, taking the strength average value of the rest two test pieces as a test result;
(3) taking the arithmetic mean value of the bonding strength test values of the three test pieces as a test result, adding three test pieces when the difference between the bonding strength test values of the two test pieces and the mean value is more than 20 percent of the mean value, and combining the test results of the six test pieces for calculation; and when the difference between the bonding strength test values of the six test pieces and the average value is not more than 20 percent of the average value, rejecting the test values with the difference between the bonding strength test values of the six test pieces and the average value being more than 20 percent of the average value, taking the rest test piece strength average value as a test result, and when the difference between the bonding strength test values of the six test pieces and the average value is more than 20 percent of the average value, the test is invalid, analyzing the reason, and selecting the test part again to conduct the test.
2. The test method for testing the bonding strength of the shotcrete and the surrounding rock in situ according to claim 1, wherein the base plate of the reaction frame further comprises a lug plate protruding from the edge of the base plate, and a hanging hole is formed in the middle of the lug plate.
3. The test method for detecting the bonding strength of the shotcrete and the surrounding rock according to claim 2, wherein screw bases for receiving the screws are uniformly distributed on the bottom plate, and the screw bases are provided with recesses in the middle.
4. The test method for testing the bonding strength of shotcrete and surrounding rock in situ according to claim 2, wherein the steel bars and the dowel bars are connected by steel cables.
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| CN110514585B (en) * | 2019-09-10 | 2024-07-23 | 中国水利水电第五工程局有限公司 | Sprayed concrete and surrounding rock bonding strength measuring device |
| CN111766200B (en) * | 2020-06-29 | 2022-08-09 | 中国人民解放军陆军工程大学 | Test device and method for measuring dynamic bonding strength of sprayed concrete under blasting disturbance |
| CN113252552B (en) * | 2021-04-13 | 2022-11-08 | 中铁十二局集团有限公司 | Test method for detecting bonding strength between sprayed concrete and surrounding rock |
| CN114481852A (en) * | 2022-03-01 | 2022-05-13 | 中建二局第三建筑工程有限公司 | Method for dismantling steel bar for bridge pier column construction |
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