An in-situ testing device for shear strength between asphalt road surface and base layer using the oblique-cut cylinder method

Abstract

An in-situ detection device for the shear strength between the surface layer and the base layer of an asphalt road using the inclined cylinder method, comprising a metal sleeve that covers a shear strength sample in a circular pit in the surface layer; a hydraulic jack, a spherical bearing, and a reaction device are arranged on the metal sleeve in sequence; the hydraulic jack is connected to a hydraulic pump through a pressure pipe; the bottom of the reaction device is buried in the surface layer and the shear strength sample, the metal sleeve, the hydraulic jack, and the spherical bearing are covered thereunder; the longitudinal axes of the shear strength sample, the metal sleeve, and the hydraulic jack are coaxial. The present invention applies a load to the shear strength sample through a detection device and decomposes it into a vertical load and a horizontal load between layers until the shear strength sample is sheared and damaged between layers, reads the maximum load, and calculates the shear strength based on the shear area, which is highly practical and accurate in detection.

Description

Technical Field

[0001] The invention relates to an in-situ detection device for the shear strength between a surface layer and a base layer of an asphalt road using an oblique-cut cylinder method. Background Art

[0002] Slippage between the surface layer and the base layer is a common disease of semi-rigid asphalt roads. When paving, the surface layer of the asphalt road and the semi-rigid base layer (such as the cement stabilized layer) need to be sufficiently vibrated and rolled to make the surface of the semi-rigid base layer relatively flat and dense, which objectively causes the friction resistance on the interlayer interface between it and the surface layer to be reduced and lower than the strength of the mixture itself, and its strength composition is transformed into dependence on bonding force. If there is no effective material and process to deal with the interlayer bonding, and the condition of not less than the strength of the mixture itself is not met, the interlayer bonding surface will become a weak point of road structure damage.

[0003] With the development of society, the number of vehicles on the road is increasing, and heavy-loaded and overloaded vehicles are common. The shear stress between the road surface and the base layer is large. If the shear strength between the surface layer and the base layer is not enough to resist this shear effect, the surface layer will slip and fail. Therefore, in-situ testing of the shear strength between the surface layer and the base layer has become a very important task.

[0004] Relevant design standards point out that shear stress is generated by the combined effect of vertical and horizontal loads from wheels, and the detection method should consider both vertical and horizontal loads. At present, there is no standard method for in-situ detection of shear strength between asphalt concrete road surface and base layers. Some existing research results only consider horizontal loads because they cannot effectively apply vertical loads, resulting in test results that do not conform to the actual situation and are not very convincing. Therefore, design creativity is needed. Summary of the invention

[0005] The present invention proposes an in-situ detection device for the shear strength between the surface layer and the base layer of an asphalt road using the inclined cylinder method, which has strong practicality, accurate detection and reasonable design, and a detection method using the device. The detection device and method can solve the problem that there is no standard method for in-situ detection of the shear strength between the surface layer and the base layer of an asphalt road.

[0006] The technical solution adopted by the present invention is: an in-situ detection device for the shear strength between the surface layer and the base layer of an asphalt road by the inclined cylinder method, comprising a metal sleeve that covers the shear strength sample in the circular pit of the surface layer; a hydraulic jack, a spherical bearing, and a reaction device are arranged on the metal sleeve in sequence; the hydraulic jack is connected to the hydraulic pump through a pressure pipe; the bottom of the reaction device is buried in the surface layer and the shear strength sample, the metal sleeve, the hydraulic jack, and the spherical bearing cover are arranged thereunder; the longitudinal axes of the shear strength sample, the metal sleeve, and the hydraulic jack are coaxial. The present invention applies a load to the shear strength sample through the detection device and decomposes it into a vertical load and a horizontal load between layers until the shear strength sample is sheared and destroyed between layers, the maximum load is read, and the shear strength is calculated based on the shear area.

[0007] Furthermore, the surface layer has a thickness of 100mm-200mm.

[0008] Furthermore, the circular pit is a cylinder, the top surface of which has a diameter of 400 mm and is flush with the surface of the surface layer, and the bottom surface is connected to the top surface between the layers.

[0009] Furthermore, the shear strength specimen is an oblique cut cylinder, with the longitudinal axis and the bottom surface at an angle of 45°, and the longitudinal axis and the top surface at an angle of 90°; the bottom surface is an oblique cut surface and an ellipse and is flush with the top surface between the layers, the major axis of the bottom ellipse is in the same straight line as the diameter of the bottom surface of the circular pit, the distance between the end point of the major axis of the bottom ellipse and the side wall of the circular pit meets the operating requirements, the top surface is a perfect circle and the highest point is flush with the surface of the surface layer; the major axis of the bottom ellipse is 150mm, the minor axis of the ellipse is 106mm, and the diameter of the perfect circle of the top surface is 106mm.

[0010] Furthermore, the metal sleeve comprises a lower beveled annulus and an upper cylinder; the inner cavity of the lower beveled annulus can be inserted into the shear strength test specimen, the top surface is parallel to the top surface of the shear strength test specimen, the inner circle diameter of the top surface is 106.1mm-107mm, the bottom surface is parallel to the bottom surface of the shear strength test specimen and is 1mm-2mm higher than the bottom surface of the shear strength test specimen, and the wall thickness is 10mm-20mm; the outer circle edge line of the bottom surface of the upper cylinder coincides with the outer circle edge line of the top surface of the beveled annulus and the bottom surface is bonded to the top surface of the shear strength test specimen by epoxy adhesive, the height of the cylinder is at least 10mm, and the middle of the top surface contacts the bottom surface of the hydraulic jack.

[0011] Furthermore, the hydraulic pump is equipped with a digital pressure gauge with a peak value storage function.

[0012] Furthermore, the reaction force device includes a metal reaction force beam, a reaction force screw and a reaction force nut.

[0013] Furthermore, the metal reaction beam is a rectangular plate, the bottom and top surfaces of which are perpendicular to the longitudinal axis of the shear strength test specimen, and a connecting circular hole is symmetrically drilled at each end, which passes through the top and bottom and connects to the reaction screw rod. The middle of the bottom surface contacts the top surface of the hydraulic jack through a spherical support.

[0014] Furthermore, the reaction screw is symmetrically arranged on both sides of the shear strength specimen, with its longitudinal axis parallel to and in the same plane as the longitudinal axis of the shear strength specimen, its bottom buried in the matching anchor hole in the surface layer through chemical anchoring glue, its top passing through the connecting circular hole and being tightened with the matching reaction nut, and the distance between the side wall of the anchor hole and the side wall of the circular pit is at least 50 mm.

[0015] The beneficial effects of the present invention are as follows: (1) During the testing process, a load is applied to the shear strength specimen and decomposed into a vertical load and a horizontal load between layers until the shear strength specimen is sheared and damaged between layers. The shear strength is calculated based on the shear area, which solves the problem that some existing research results cannot effectively apply vertical loads, resulting in test results that do not conform to the actual situation and are not convincing. The present invention has strong practicality and accurate testing. (2) The testing device is reasonably designed, and the instruments and spare parts used are purchased, processed, assembled and carried easily, which greatly improves the promotion value. (3) The problem that there is no standard method for in-situ testing of the shear strength between the surface layer and the base layer of asphalt concrete roads is solved, and technical support is provided for construction acceptance, design reinforcement, quality supervision, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a front view schematic diagram of the use of the present invention.

[0017] Figure 2 It is a schematic diagram of the AA cross section of the present invention.

[0018] Figure 3 It is a schematic diagram of the BB cross section of the present invention.

[0019] Figure 4 It is a schematic diagram of the CC cross section of the present invention.

[0020] Figure 5 It is a schematic diagram of the DD cross section of the present invention.

[0021] Figure 6 It is a schematic top view of the structure of the present invention.

[0022] Figure 7 It is a schematic cross-sectional view of structure EE of the present invention.

[0023] Figure 8 It is a schematic cross-sectional view of the structure FF of the present invention.

[0024] Fig. 9 It is a schematic cross-sectional view of structure GG of the present invention.

[0025] Fig.10 It is a schematic diagram of drilling a shear strength specimen of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0027] Reference Figure 1-10 , an in-situ detection device for the shear strength between the surface layer and the base layer of an asphalt road by the inclined cylinder method, comprising a metal sleeve 9 that covers a shear strength test sample 15 in a circular pit 12 in the surface layer 11; a hydraulic jack 8, a spherical support 5, and a reaction device 6 are arranged on the metal sleeve 9 in sequence; the hydraulic jack 8 is connected to a hydraulic pump 2 through a pressure pipe 1; the bottom of the reaction device 6 is buried in the surface layer 11 and the shear strength test sample 15, the metal sleeve 9, the hydraulic jack 8, and the spherical support 5 are covered thereunder; the longitudinal axes of the shear strength test sample 15, the metal sleeve 9, and the hydraulic jack 8 are coaxial. The present invention applies a load to the shear strength test sample 15 through a detection device and decomposes it into a vertical load and a horizontal load in the interlayer 18 until the shear strength test sample 15 is sheared and damaged in the interlayer 18, reads the maximum load, and calculates the shear strength according to the shear area.

[0028] The surface layer 11 described in this embodiment has a thickness of 180 mm.

[0029] The circular pit 12 described in this embodiment is a cylinder, with a top diameter of 400 mm and flush with the surface of the surface layer 11, a bottom surface connected to the top surface of the interlayer 18, and a depth of 180 mm.

[0030] The shear strength test piece 15 described in this embodiment is a beveled cylinder, with an angle of 45° between the longitudinal axis and the bottom surface, and an angle of 90° between the longitudinal axis and the top surface; the bottom surface is a beveled surface and an ellipse and is flush with the top surface of the interlayer 18, the major axis of the bottom ellipse is in the same straight line with the bottom diameter of the circular pit 12, one end of the major axis of the bottom ellipse is 30mm away from the side wall of the circular pit 12, the top surface is a perfect circle and the highest point is flush with the surface of the surface layer 11; the major axis of the bottom ellipse is 150mm, the minor axis of the ellipse is 106mm, and the diameter of the perfect circle of the top surface is 106mm.

[0031] The metal sleeve 9 described in this embodiment includes a lower beveled circular ring body and an upper cylinder; the inner cavity 10 of the lower beveled circular ring body can be inserted into the shear strength test specimen 15, the top surface is parallel to the top surface of the shear strength test specimen 15, the inner ring diameter of the top surface is 106.5mm, the bottom surface is parallel to the bottom surface of the shear strength test specimen 15 and is 1.5mm higher than the bottom surface of the shear strength test specimen 15, and the wall thickness is 16mm; the outer ring edge line of the bottom surface of the upper cylinder coincides with the outer ring edge line of the top surface of the beveled circular ring body, and the bottom surface is bonded to the top surface of the shear strength test specimen 15 by an epoxy adhesive 17, the height of the cylinder is 16mm, and the middle of the top surface contacts the bottom surface of the hydraulic jack 8.

[0032] The hydraulic pump 2 described in this embodiment is equipped with a digital pressure gauge 3 with a peak value storage function.

[0033] The reaction device 6 described in this embodiment includes a metal reaction beam 4 , a reaction screw 7 and a reaction nut 16 .

[0034] The metal reaction beam 4 described in this embodiment is a rectangular plate, length × width × thickness = 560mm × 60mm × 20mm, the bottom and top surfaces are perpendicular to the longitudinal axis of the shear strength test specimen 15, and a connecting circular hole 19 is symmetrically drilled at both ends, which passes through the top and bottom and is connected to the reaction screw 7. The hole diameter is 22mm, and the distance between the hole and the hole is 500mm. The middle of the bottom surface contacts the top surface of the hydraulic jack 8 through the spherical support 5.

[0035] The reaction screw 7 described in this embodiment has a length of 400 mm and a specification of 18 mm. It is symmetrically arranged on both sides of the shear strength test specimen 15, and its longitudinal axis is parallel to and in the same plane as the longitudinal axis of the shear strength test specimen 15. Its bottom is buried in the matching anchor hole 19 in the surface layer 11 through a chemical anchoring glue 21. The anchor hole 19 has a diameter of 24 mm and a depth of 130 mm. Its top passes through the connecting circular hole 20 and is tightened with the matching reaction nut 16. The distance between the side wall of the anchor hole 19 and the side wall of the circular pit 12 is greater than 50 mm.

[0036] The detection steps of this embodiment are as follows: (1) Use a road surface cutting machine to cut the road surface, adjust the cutting angle so that the angle between the cutting surface and the surface layer 11 is 135°, and the depth along the cutting surface is 120 mm; (2) Fix the adjustable angle coring machine 22 on the surface of the surface layer 11, install a small diamond thin-walled hollow drill bit 23 with an inner diameter of 106 mm and a length of 420 mm, adjust the angle and distance of the adjustable angle coring machine 22 so that the angle between the small diamond thin-walled hollow drill bit 23 and the cutting surface is 90°; (3) Start the adjustable angle coring machine 22, and the small diamond thin-walled hollow drill bit 23 drills in, and its minimum drilling depth is the bottom surface of the interlayer 18, forming a shear strength test sample 15; (4) Stop the adjustable angle coring machine 22, replace it with a small diamond thin-walled hollow drill bit 23 with an outer diameter of 400 mm m, a large diamond thin-walled hollow drill bit 24 with a length of 420 mm, adjust the angle and distance of the adjustable angle coring machine 22 so that the large diamond thin-walled hollow drill bit 24 is perpendicular to the surface of the surface layer 11, and the longitudinal axis of the large diamond thin-walled hollow drill bit 24 is in the same plane as the major axis of the ellipse on the bottom surface of the shear strength specimen 15; (5) Start the adjustable angle coring machine 22, and the large diamond thin-walled hollow drill bit 24 drills in, and its minimum drilling depth is the maximum drilling depth of the small diamond thin-walled hollow drill bit 23, forming the side wall of the circular pit 12, and the end point of the major axis of the bottom surface ellipse is 30 mm away from the side wall of the circular pit 12; (6) Remove the adjustable angle coring machine 22, and chisel away the surface layer 11 and the base layer 14 road between the two drill holes; (7) Use a self-compacting non-shrinkage The grouting material 13 is poured into the removed part. The top surface of the self-compacting non-shrinkage grouting material 13 is in the same plane as the top surface of the interlayer 18, forming a circular pit 12; (8) Use an electric hammer to drill holes in the surface layer 11. The drilling angle is parallel to the longitudinal axis of the shear strength specimen 15. The drilling point is 250mm away from the longitudinal axis of the shear strength specimen 15. Anchor holes 19 are drilled symmetrically on both sides of the shear strength specimen 15. The hole diameter is 24mm and the depth is 130mm. The longitudinal axis of the anchor hole 19 is in the same plane as the longitudinal axis of the shear strength specimen 15. Anchor glue 21 is poured into the anchor hole 19 and the reaction screw 7 is rotated and inserted; (9) Epoxy adhesive 17 is applied to the top surface of the shear strength specimen 15. The metal sleeve 9 is inserted into the shear strength specimen 15. The upper cylindrical portion of the metal sleeve 9 is slightly pressed by hand. , so that the shear strength specimen 15 is bonded to the metal sleeve 9, and after the self-compacting non-shrinkage grouting material 13, anchoring glue 21, and epoxy adhesive 17 solidify, the hydraulic jack 8 and the spherical bearing 5 are placed on the metal sleeve 9 in sequence, and the reaction screw 7 is inserted into the connecting hole 20, so that the middle of the bottom surface of the metal reaction beam 4 contacts the top surface of the hydraulic jack 8 through the spherical bearing 5, and the reaction nut 16 is tightened; (10) The hydraulic jack 8 is connected to the hydraulic pump 2 through the pressure pipe 1, and the hydraulic pump 2 is started to load, and a load is applied to the shear strength specimen 15 and decomposed into a vertical load and a horizontal load in the interlayer 18 until the shear strength specimen 15 is sheared and damaged in the interlayer 18, and the maximum load is read, and the shear strength is calculated based on the shear area.

Claims

1. An in-situ testing device for the shear strength between the surface layer and the base layer of an asphalt road by using an oblique cylinder method, characterized in that: It includes a metal sleeve for shear strength test specimen in the circular pit of the surface layer; the shear strength test specimen is a beveled cylinder, the angle between the longitudinal axis and the bottom surface is 45°, and the angle between the longitudinal axis and the top surface is 90°; the bottom surface is a beveled surface and an ellipse and is flush with the top surface of the interlayer, the major axis of the bottom ellipse is in the same straight line with the diameter of the bottom surface of the circular pit, the distance between the end point of the major axis of the bottom ellipse and the side wall of the circular pit meets the operation requirements, the top surface is a perfect circle and the highest point is flush with the surface of the surface layer; the major axis of the bottom ellipse is 150mm, the minor axis of the ellipse is 106mm, and the diameter of the perfect circle of the top surface is 106mm; the metal sleeve includes a lower beveled circular ring body and an upper cylinder; the inner cavity of the lower beveled circular ring body can be sheathed with the shear strength test specimen, the top surface is parallel to the top surface of the shear strength test specimen, and the inner circle diameter of the top surface is 106.1mm- 107mm, the bottom surface is parallel to the bottom surface of the shear strength specimen and is 1mm-2mm higher than the bottom surface of the shear strength specimen, and the wall thickness is 10mm-20mm; the circular edge line of the upper cylindrical bottom surface coincides with the outer ring edge line of the top surface of the chamfered circular ring body, and the bottom surface is bonded to the top surface of the shear strength specimen by epoxy adhesive, the height of the cylinder is at least 10mm, and the middle of the top surface is in contact with the bottom surface of the hydraulic jack; the hydraulic jack, spherical bearing, and reaction device are arranged on the metal sleeve in sequence; the hydraulic jack is connected to the hydraulic pump through a pressure pipe; the bottom of the reaction device is buried in the surface layer and the shear strength specimen, metal sleeve, hydraulic jack, and spherical bearing cover are arranged thereunder; the longitudinal axes of the shear strength specimen, metal sleeve, and hydraulic jack are coaxial.

2. According to claim 1, an in-situ detection device for the shear strength between the asphalt pavement surface layer and the base layer using the oblique cylinder method, characterized in that: The surface layer has a thickness of 100mm-200mm.

3. The in-situ detection device for the shear strength between the asphalt pavement surface layer and the base layer using the oblique cylinder method according to claim 1 is characterized by: The circular pit is a cylinder with a top surface diameter of 400 mm and flush with the surface of the surface layer, and a bottom surface connected to the top surface between the layers.

4. The in-situ detection device for the shear strength between the asphalt pavement surface layer and the base layer using the oblique cylinder method according to claim 1 is characterized by: The oil pressure pump is equipped with a digital pressure gauge with a peak value storage function.

5. The in-situ detection device for the shear strength between the asphalt pavement surface layer and the base layer using the oblique cylinder method according to claim 1 is characterized by: The reaction force device comprises a metal reaction force beam, a reaction force screw rod and a reaction force nut.

6. The in-situ detection device for the shear strength between the asphalt pavement surface layer and the base layer using the oblique cylinder method according to claim 5 is characterized by: The metal reaction beam is a rectangular plate, the bottom and top surfaces of which are perpendicular to the longitudinal axis of the shear strength test specimen, and a connecting circular hole is symmetrically drilled at each end, which passes through the top and bottom and connects to the reaction screw rod. The middle of the bottom surface contacts the top surface of the hydraulic jack through a spherical support.

7. The in-situ detection device for the shear strength between the asphalt pavement surface layer and the base layer using the oblique cylinder method according to claim 5 is characterized by: The reaction screw is symmetrically arranged on both sides of the shear strength specimen, with its longitudinal axis parallel to and in the same plane as the longitudinal axis of the shear strength specimen. The bottom is buried in the matching anchor hole in the surface layer through chemical anchoring glue, and the top passes through the connecting circular hole and is tightened with the matching reaction nut. The distance between the side wall of the anchor hole and the side wall of the circular pit is at least 50 mm.

8. A detection method using the in-situ detection device for shear strength between asphalt pavement surface layer and base layer using the oblique cylinder method as claimed in claim 1, characterized in that: The test includes the following steps: (1) using a pavement cutting machine to cut the pavement, adjusting the cutting angle so that the angle between the cutting surface and the surface layer is 135°, and the depth along the cutting surface is at least 120 mm; (2) fixing an adjustable angle coring machine on the surface of the surface layer 11, installing a small diamond thin-wall hollow drill bit with an inner diameter of 106 mm and a length of at least 420 mm, adjusting the angle and distance of the adjustable angle coring machine so that the angle between the diamond thin-wall hollow drill bit and the cutting surface is 90°; (3) starting the adjustable angle coring machine, and drilling with the small diamond thin-wall hollow drill bit, the minimum drilling depth of which is the bottom surface between the layers, to form a shear strength test. (4) Stop the adjustable angle coring machine, replace it with a large diamond thin-wall hollow drill bit with an outer diameter of 400 mm and a length of at least 420 mm, and adjust the angle and distance of the adjustable angle coring machine so that the large diamond thin-wall hollow drill bit is perpendicular to the surface of the surface layer, and the longitudinal axis of the large diamond thin-wall hollow drill bit is in the same plane as the major axis of the ellipse on the bottom surface of the shear strength specimen; (5) Start the adjustable angle coring machine, and drill with the large diamond thin-wall hollow drill bit. The minimum drilling depth is the maximum drilling depth of the small diamond thin-wall hollow drill bit, forming the side wall of the circular pit, and the distance between one end of the major axis of the bottom ellipse and the side wall of the circular pit is 30 mm; (6) Remove the adjustable angle coring machine and chisel out the surface layer and base road between the two drilled holes; (7) Use self-compacting non-shrinkage grouting material to fill the chiseled part, and the top surface of the self-compacting non-shrinkage grouting material should be in the same plane as the top surface between the layers; (8) Use an electric hammer to drill holes in the surface layer, and the drilling angle should be parallel to the longitudinal axis of the shear strength specimen. Drill anchor holes symmetrically on both sides of the shear strength specimen, pour anchor glue into the holes, and rotate the reaction screw to insert; (9) Apply epoxy adhesive to the top surface of the shear strength specimen, insert the metal sleeve into the shear strength specimen, and slightly press the upper cylinder of the metal sleeve with your hand to make the shear strength specimen and the metal sleeve close to each other. The sleeve is bonded, and after the self-compacting non-shrinkage grouting material, anchor glue, and epoxy adhesive solidify, a hydraulic jack and a spherical bearing are placed on the metal sleeve in sequence, and the reaction screw is inserted into the connecting circular hole so that the middle of the bottom surface of the metal reaction beam contacts the top surface of the hydraulic jack through the spherical bearing, and the reaction nut is tightened; (10) The hydraulic jack is connected to the hydraulic pump through a pressure pipe, and the hydraulic pump is started to load. A load is applied to the shear strength specimen and decomposed into a vertical load and a horizontal load between layers until the shear strength specimen is sheared and destroyed between layers. The maximum load is read, and the shear strength is calculated based on the shear area.

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