JP3684376B2 - In-situ shear tester - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shear tester for measuring the shear strength of slope surface soil, etc. Specifically, a shear box was attached to a specimen cut into an upright column shape on the original ground and the original soil particle structure was retained. The present invention relates to an on-site shear tester that measures shear strength in a state.
[0002]
[Prior art]
In order to prevent landslides and landslides due to torrential rain, earthquakes, etc., the shear strength of the slope surface soil was measured with a shear tester, and the stability of landslides was examined based on the measurement results. Judging the validity of strength constants used in the design of countermeasures.
[0003]
By the way, in the shear tester, in order to measure the shear strength with high accuracy, it is preferable to directly measure in a state in which the soil particle structure in the original position is maintained. Various in-situ shear test machines that measure shear strength by attaching a slab have been proposed. As an in-situ shear tester, one shear box is attached to the specimen, and the shear box is horizontally moved by the shear force loading means in a state where a predetermined normal force is applied to the entire head of the specimen by the vertical force loading means. The mainstream type is a one-sided shear type in which the specimen is sheared between the ground and the shear box. However, in order to apply a horizontal reaction force during shearing, the shear force loading means is supported by a hole wall or a press plate dug around the specimen, and a vertical reaction force by the normal force loading means is provided. The vertical force loading means is applied with a weight such as an iron lump or concrete, pressed down with a power shovel, or fixed to the ground with an earth anchor. For this reason, the auxiliary equipment for installing the on-site shear tester requires a large-scale and large space, and there are problems such as requiring a lot of time, labor, and cost for the installation work.
[0004]
Therefore, for example, as described in JP-A-8-247913, a shear box is guided and supported in a horizontal direction by a guide member on a base provided with an opening through which a specimen is passed, and shearing force loading means is provided on the base. A field shear tester of the single-sided shear type supported by a fixed wall and supported by a reaction force support provided with a normal force loading means on the base has been proposed. Also, soil and foundation, Vol. 31, no. 2, pages 27-31 and 23rd Geotechnical Research Presentation (June 1988), Research Papers Nos. 1755-1756, the shear box is a lower shear box, an intermediate shear box, and an upper shear box. It consists of a box, the lower shear box and the upper shear box are connected by a U-shaped frame so that the upper shear box can move up and down, the intermediate shear box is connected to the shearing force loading means, and the shearing force loading means is the U-shaped frame And a vertical force loading means is provided on a steel frame installed across the shear box, and the intermediate shear box is sheared between the lower shear box and the upper shear box by horizontally moving the intermediate shear box. A field shear tester of the two-sided shear type has been proposed.
[0005]
[Problems to be solved by the invention]
However, the conventional one-side shear type in-situ shear testing machine applies both the horizontal reaction force and the vertical reaction force by the base, so that the dimensions and weight of the base become large and the installation work space becomes large. It is difficult to sufficiently reduce time, labor, and cost. In addition, since the base and the shear box are attached to the specimen together, the specimen must be attached so as not to break, and the mounting work requires a lot of time and labor.
[0006]
On the other hand, for the conventional two-plane shear type in-situ shear tester, the steel frame is installed across the three-tiered cardboard box, and a vertical reaction force is applied by placing an iron ingot. The size and weight of the frame increase, and it is difficult to sufficiently reduce the installation time and labor. In addition, since the intermediate shear box is not guided and supported, it is difficult to obtain a horizontal shear plane, and when the specimen expands during shearing, the upper shear box moves up, and errors in vertical stress are likely to occur. Since the shear box and the upper shear box are in contact with each other, it is difficult to say that the measurement accuracy is good because the shearing force tends to cause an error in the shearing stress.
[0007]
The present invention has been made to solve the above-mentioned conventional problems, and its problem is to provide an on-site shear test machine that can reduce factors that adversely affect measurement accuracy and can easily and quickly perform installation work. There is.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention attaches a lower shear box and an upper shear box to a specimen cut out and formed into an upright column on the original ground, and applies a predetermined force to the entire head of the specimen by vertical force loading means. With the normal force applied, move the lower shear box horizontally using the shear force loading means, shear the specimen between the lower shear box, the ground and the upper shear box, and directly measure the shear strength of the specimen. An in-situ shear tester, where the lower shear box is guided and supported in a horizontal direction by a shear loading frame installed horizontally around the specimen, and a gap is provided so that the upper shear box does not contact the lower shear box. It is fixedly installed on the shear force loading frame, the shear force loading means is installed by connecting the lower shear box and the shear force loading frame, and the vertical force loading means is installed on the vertical force loading frame fixed to the shear force loading frame. Special that It is set to.
[0009]
It is preferable that the shear load carrying frame is fixed and held on the original ground by a grooved pile having a screw anchor or a pressing plate. It is preferable that the upper shear box is fixedly installed on the shearing force loading frame by vertical adjustment and fixing means including bolts and nuts. The shear force loading frame has a pair of front and rear guide support frame portions that horizontally support and support the lower shear box and a horizontal reaction force support frame portion that supports the shear force loading means arranged in parallel to each other, and these are paired on the left and right sides. It is preferable that the vertical shape is fixedly connected with a bolt and the overall shape is rectangular.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. In the figure, reference numeral 1 denotes a specimen, which is cut and formed into an upright column shape on the original ground. 2 is a field shear tester, 3 is a lower shear box, 4 is an upper shear box, and 5 is a shear force loading frame. The shear force loading frame 5 includes a pair of front and rear guide support frame portions 6 that horizontally guide and support the lower shear box 3, a horizontal reaction force support frame portion 7 that supports shear force loading means 17 to be described later, and a pair of left and right connecting them. 2 and the entire shape is assembled in a rectangular shape as shown in FIG. As shown in FIG. 6A, the assembly of the shear force loading frame 5 is carried out after the lower shear box 3 is mounted on the specimen 1 and then protrudes forward and backward of the lower shear box 3 as shown in FIG. 6B. The front and rear guide support frame portions 6 are installed so that the guide sleeves 10 are engaged with the respective pair of guide rods 9 provided in this manner, and are provided on each guide support frame portion 6 as shown in FIG. The L-shaped mounting plate 15 of the upper shear box is attached by the vertical adjustment / fixing means 14 including the bolt 11, the upper nut 12, and the lower nut 13, and the lower nut 13 is loosened as shown in FIG. The upper shear box 4 is lowered so as to come into contact with the lower shear box 3, the lower shear box 3 and the upper shear box 4 are fastened and fixed by the locking bolts 16, the upper nut 12 is lowered and the lower nut 13 is raised, and the mounting plate 15 is fixed. Thereafter, the horizontal reaction force support frame portion 7 is installed so that the front end of the shear force loading means 17 penetrates the rear guide support frame portion 6 and engages with the lower shear box 3, and a pair of left and right vertical frame portions 8 are installed. Are fixed to the frame portions 6 and 7 with bolts 18 and assembled into a rectangular shape. The height of the upper shear box 4 is lower than that of the lower shear box 3 and is set to about 40 percent of the lower shear box 3, for example. The upper shear box 4 is fixed to the vertical part of the L-shaped mounting plate 15 by bolts 19 and nuts 20 and can be adjusted to match the lower shear box 3.
[0011]
The shear force loading means 17 includes a shear force measuring force gauge 23 provided between a screw jacket 21 that generates a shear force and a pressing portion 22 that is engaged with the lower shear box 3 and transmits the shear force. By operating the screw jack 21 at 24, the shear force applied to the lower shear box 3 is measured by a shear force measuring force meter 23. Reference numeral 25 denotes a horizontal displacement contactor indicating the horizontal displacement of the lower shear box 3, and is attached to the vertical frame portion 8 of the shear force loading frame so that the horizontal displacement meter 26 contacts the horizontal displacement contactor 25 as shown in FIG. It has been.
[0012]
Reference numeral 27 denotes a vertical force loading frame, which is integrally formed in a U-shape downward with a groove mold material. After assembling the shearing force loading frame 5, it straddles the upper shear box 4 as shown in FIG. It is fixed to the vertical frame portion 8 of the frame with bolts 28. Reference numeral 29 denotes a vertical force loading means, and a vertical force measuring force meter 32 is provided between a hydraulic operating portion 30 of the hydraulic jack and a pressure plate 31 that contacts the entire head of the specimen 1 and transmits the vertical force. The vertical force applied to the specimen 1 is measured by a vertical force measuring force meter 32 by operating a hydraulic pressure generating portion (not shown) of the hydraulic jack. The vertical force loading means 29 is attached to the vertical force loading frame 27 so that the pressure plate 31 coincides with the entire head of the specimen 1 immediately above the upper shear box 4. The pressure plate 31 is provided with a plurality of drain holes (not shown) penetrating vertically so as to discharge moisture from the specimen 1 during pressurization. Reference numeral 33 denotes a vertical displacement contactor indicating the vertical displacement of the specimen 1, and is attached to the vertical force loading frame 27 so that the vertical force displacement meter 34 contacts the vertical displacement contactor 33 as shown in FIGS. 1 and 3. ing.
[0013]
Reference numeral 35 denotes a screw anchor for fixing the shear force loading frame 5 to the ground, and a cylindrical shape provided at both ends of the vertical frame portion 8 of the shear force loading frame after the vertical force loading frame 27 is attached to the shear force loading frame 5. Screwed in the upper part of the screw anchor 35 after being inserted into the fixing part 35, rotated with a wrench and screwed into the ground, screwed in a predetermined amount as shown in FIG. The anchor nut 38 is screwed into (not shown) and is placed in contact with the upper surface of the stopper 37 and tightened. The screw anchor 35 is firmly held on the ground and can sufficiently apply a vertical reaction force. In addition, as shown in FIG. 8, you may be the grooved pile 39 which has the press plate 40 in a head. This grooved pile 39 is used when penetration of the squeeze anchor 35 is difficult, and is driven into the ground so as to press and hold the vertical frame portion 8 of the shear force loading frame with the pressing plate 40.
[0014]
The embodiment of the present invention is configured as described above, and its operation will be described together with a test method. The specimen 1 is cut out, and Toyoura standard sand is laid so that the place where the in-situ shear test machine 2 is installed is horizontal, and the upper shear box 4 is installed in the process shown in FIG. After fixing the upper shear box 4 with the locking bolt 16, the portion protruding from the upper shear box 4 is removed with a spatula, shavings are put in the gap, and the brush is finished. Next, as described above, the installation of the shear force loading means 17, the assembly of the shear force loading frame 5, the attachment of the vertical force loading frame 27, and the fixing of the shear force loading frame 5 by the screw anchor 35 are performed in order. The hydraulic pressure generating unit and the hydraulic operating unit 30 are connected, and the horizontal displacement meter 26 and the vertical displacement meter 34 are attached as described above. Thus, the preparation process is completed, and the consolidation process is performed.
[0015]
In the consolidation process, the lower shear box 3 and the upper shear box 4 are fastened and fixed with a locking bolt 16 as shown in FIGS. It is designed not to leak from between. A filter paper (not shown) is placed on the pressure surface of the specimen 1 and the hydraulic pressure generator (not shown) of the hydraulic jack is manually operated gently, and the vertical force measuring force meter 32 is supported upward while being manually supported. Then, the vertical force measuring force meter 32 is temporarily stopped at a position where the scale starts to move slightly, and the vertical force measuring force meter 32 is set to zero. Next, a predetermined restraint pressure is loaded, a consolidation time is set, the initial value of the vertical displacement meter 34 is read, and then the vertical displacement meter 34 is read and recorded in units of 1/100 mm. During the consolidation time, the hydraulic pressure generating portion (not shown) of the hydraulic jack is adjusted so that the restraint pressure is always in a constant pressure state.
[0016]
After the consolidation process is completed, a shearing process is performed. The lower shear box 3 and the upper shear box 4 are in a state of being fastened and fixed by a locking bolt 16 as shown in FIG. 4 at the end of the consolidation process. In the shearing process, the lower shear box 3 and the upper shear box 4 A gap is formed as shown in FIG. 5 so as not to cause a friction force upon contact. First, the upper nut 12 of the vertical adjustment / fixing means is loosened so that the distance between the top surface of the locking bolt 16 and the upper surface of the upper shear box 4 is the sum of the thickness of the locking bolt 16 and the gap dimension. Loosen the locking bolt 16 while measuring with a caliper. Next, the lower nut 13 of the vertical adjustment / fixing means is raised, the upper surface of the upper shear box 4 is brought into contact with the lower surface of the head of the locking bolt 16, and the upper nut 12 of the vertical adjustment / fixing means is fastened to tighten the upper shear. The box 4 is fixed. After the adjustment of the gap is completed, the locking bolt 16 is pulled out and the shearing force loading means 17 is activated to start shearing. By slowly turning the handle 24, the screw jack 21 is moved forward, temporarily stopped at the position where the graduations of the shear force measuring force gauge 23 and the horizontal displacement gauge 26 slightly move, and the shear force measuring force gauge 23 and the horizontal displacement gauge 26 are moved. Is set to zero. Then, after applying a predetermined restraining pressure to the specimen 1 by the vertical force loading means 29, the initial value of the vertical displacement meter 34 is read, shearing is started at a predetermined shear rate, and the shear force and the vertical displacement corresponding to the shear displacement are read. Are sequentially recorded, and when the shear discontinuation displacement is reached, the screw jack 21 is stopped. At that time, the specimen 1 is sheared on two surfaces between the lower shear box 3 and the ground and upper shear box 4, for example, as shown in FIG. The lower shear box 3 is guided by the guide support frame portion 6 and moved horizontally, and the upper shear box 4 is fixed to the guide support frame portion 6 and does not move up and down. Further, since the upper shear box 4 is fixedly installed with a clearance from the lower shear box 4, no friction force is generated between the lower shear box 3 and the upper shear box 4, and the shear force by the shear force loading means 17 is accurate. The horizontal displacement also appears accurately. In the consolidation process and the shearing process, a vertical force is applied to the specimen 1 by the normal force loading means 29. However, the vertical force loading frame 27 is fixed integrally to the shearing force loading frame 5, and the shear force loading frame 5 is Since the screw anchor 35 is fixed to the ground and the screw anchor 35 is fastened and fixed in the pulling direction by the anchor nut 38, a sufficient vertical reaction force is applied by the screw anchor 35, and the A normal force can be applied. The restraining pressure is adjusted by a hydraulic pressure generating portion (not shown) of the hydraulic jack so as to be constant during shearing.
[0017]
After finishing the shearing process, the in-situ shear tester 2 is disassembled. The procedure for dismantling is as follows. The handle 24 of the shearing force loading means 17 is turned to cause the screw jack 21 to retreat and return to its original state. The air cock of the hydraulic pressure generating portion (not shown) of the hydraulic jack of the vertical force loading means 29 is loosened, the vertical force measuring force gauge 32 is pulled back to the original position, and the air cock is tightened. The vertical displacement meter 34 and the horizontal displacement meter 26 are removed, and the screw anchor 35 is removed by rotating it in the reverse direction with the anchor nut 38 and the stopper 37 attached, and removed from the fixing portion 36. The connection between the hydraulic pressure generating section (not shown) of the hydraulic jack and the hydraulic operating section 30 is released. Next, the vertical force loading frame 27 is removed from the shearing force loading frame 5 and the shearing force loading frame 5 is disassembled. The bolt 18 between the vertical frame portion 8 and the guide support frame portion 6 and the horizontal reaction force support frame portion 7 is pulled out, and the vertical frame portion 8 is removed. Then, the horizontal reaction force support frame portion 7 is removed from the lower shear box 3 integrally with the shear force loading means 17. The upper nut 12 of the vertical adjustment / fixing means 14 is removed, the upper shear box 4 is removed, and the sample in the upper shear box 4 is brought back. By removing the guide support frame 6 from the lower shear box 3, only the lower shear box 3 remains, and the disassembly is completed. Take the sample in the lower shear box 3 with you. As described above, since the shear force loading frame 5, the vertical force loading frame 27, the upper shear box 4 and the lower shear box 3 are assembled by bolt connection, they can be easily and quickly disassembled. And by being dismantled, it can be transported and stored in a unit that is small in volume and lightweight.
[0018]
【The invention's effect】
According to the present invention, the lower shear box is horizontally moved so that the ground is sheared in two planes with the upper shear box. Therefore, the shear force loading means is provided on the shear force loading frame installed horizontally on the ground. By supporting it, a horizontal reaction force can be sufficiently applied, and it has become possible to obtain an in-situ shear tester that is much smaller and simplified than before and has excellent installation workability.
[0019]
Since the lower shear box is guided and supported so as to move horizontally on the shear force loading frame, and the upper shear box is fixedly installed on the shear force loading frame, the specimen can be sheared almost horizontally. Since a gap is provided between the lower shear box and the upper shear box, shearing can be performed without being affected by the frictional force between the two. Therefore, it has become possible to remove factors that adversely affect the measurement result far more than before.
[0020]
In the case where the shearing load frame is fixed by the squeeze anchor, the squeeze anchor is firmly fixed and held on the ground by being penetrated into the ground and then tightened in the pulling direction by the anchor nut. As a result, the vertical reaction force can be sufficiently applied, and the normal force can be accurately applied to the specimen by means smaller than the conventional one, thereby making it possible to obtain good measurement accuracy.
[0021]
When the shear load frame is constructed such that the guide support frame, horizontal reaction force support frame, and vertical frame are assembled by bolting, the installation and disassembly work is easy and quick as well as transportation and storage. It became possible to do.
[Brief description of the drawings]
FIG. 1 is a conceptual explanatory view of an embodiment of the present invention, and is a longitudinal sectional view in a state where an in-situ shear tester is installed.
FIG. 2 is a conceptual explanatory diagram of an embodiment of the present invention, and is a plan view corresponding to FIG.
3 is a conceptual explanatory diagram of an embodiment of the present invention, and a cross-sectional view taken along line XX of FIG.
4 is an enlarged view showing a relationship between a lower shear box and an upper shear box in FIG. 1. FIG.
FIG. 5 is a conceptual explanatory diagram of an embodiment of the present invention, and is an enlarged view showing a relationship between a lower shear box and an upper shear box just before the start of a shearing process.
FIG. 6 is a conceptual explanatory diagram of an embodiment of the present invention and shows a process until an upper shear box is installed in a process of installing and installing a field shear tester on a specimen. (A) is a state where the lower shear box is mounted on the specimen, (b) is a state where the guide support frame is installed, (c) is a state where the upper shear box is installed above the lower shear box, (d) is a state where The state where the upper shear box is fastened to the lower shear box with a locking bolt is shown.
FIG. 7 is a conceptual explanatory diagram of an embodiment of the present invention, and is a cross-sectional view showing an example of a relationship between a lower shear box, an upper shear box, and a specimen at the end of shearing.
FIG. 8 is a conceptual explanatory diagram of a modification of the main part in the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Specimen 2 On-site shear testing machine 3 Lower shear box 4 Upper shear box 5 Shear force loading frame 6 Guide support frame 7 Horizontal reaction force support frame 8 Vertical frame 9 Lower shear box guide rod 10 Guide sleeve 14 Vertical adjustment Combined fixing means 15 Mounting plate 16 Locking bolt 17 Shear force loading means 29 Vertical force loading means 31 Pressure plate 35 Screw anchor 36 Fixing part 37 Stopper 38 Anchor nut 39 Grooved pile 40 Pressing plate

Claims (5)

A lower shear box (3) and an upper shear box (4) are mounted on a specimen (1) cut out and formed into an upright column on the original ground, and the entire head of the specimen (1) is mounted by a vertical force loading means (29). The lower shear box (3) is moved horizontally by the shear force loading means (17) in a state where a predetermined vertical force is applied to the lower shear box (3), the original ground and the upper shear box ( 4) In-situ shear tester (2) that directly measures the shear strength of the specimen (1), and the lower shear box (3) is installed horizontally around the specimen (1) It is guided and supported in the horizontal direction by the shearing force loading frame (5), and is fixedly installed on the shearing force loading frame (5) with a gap so that the upper shearing box (4) does not contact the lower shearing box (3). The shearing force loading means (17) connects the lower shearing box (3) and the shearing force loading frame (5). Is installed by forming a vertical force loading means (29) shear force field shear tester, characterized in that installed in the loading frame is fixed to (5) a vertical force loading frame (27). 2. The in-situ shear testing machine according to claim 1, wherein the shear force loading frame (5) is fixed and held on the original ground by a screw anchor (35). 2. The field shear test machine according to claim 1, wherein the shear force loading frame (5) is fixedly held on the raw ground by a grooved pile (39) having a pressing plate (40) at the head. The upper shear box (4) is fixedly installed on the shear force loading frame (5) by means of vertical adjustment and fixing means (14) comprising bolts (11) and nuts (12, 13). In-situ shear tester according to 3. The shear force loading frame (5) includes a pair of front and rear guide support frame portions (6) for horizontally guiding and supporting the lower shear box (3) and a horizontal reaction force support frame portion (7) for supporting the shear force loading means (17). Are arranged in parallel with each other, and these (6, 7) are fixedly connected with bolts (18) by means of a pair of left and right vertical frames (8), and the overall shape is rectangular. An in-situ shear tester according to any one of the preceding claims.

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