JP2837510B2 - Simple rock shear test equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a test device for determining the shear strength of rock.

(Prior Art) In civil engineering works such as dams and tunnels, it is extremely important to quantitatively grasp the strength of the bedrock at the location.

Among the above-mentioned strengths, methods for obtaining the shear strength include a sampling method and an in-situ test method.

That is, the sampling method is a method in which a sample is cut out from the bedrock at the location, brought back, and put on a test machine in a test room. However, it is said that this method makes it difficult to cut out a good-sized sample, and that the water content changes during the period of bringing back the sample, thereby lowering the test accuracy.

Therefore, it is desirable to conduct a test directly at this location (this is referred to as an “in-situ test”). A part of the rock is cut out in a square block shape, and the rock test is performed with a hydraulic jack or the like to perform a shear test. .

FIG. 6 is a view showing a conventional in-situ test. In the in-situ shear test, a tunnel 101 of about 2 × 2 m was dug, a test piece 103 was cut and formed on a tunnel floor 102, and a tunnel ceiling 104 was formed.
While holding down the test body 103 with the vertical jack 105 starting from
Specimen with horizontal jack 107 starting from tunnel wall 106
103 is pressed, and the applied load is measured by the load meter 108.

(Problems to be Solved by the Invention) The above test is generally performed on at least four rocks of the same rock classification. However, the above-mentioned conventional test involves a high cost per test, so that it is difficult to increase the number of samples, and it is difficult to calculate a reliable shear strength.

Further, in recent years, the number of cases where structures are supported on low-grade bedrock made of sedimentary rock, weathered granite, or the like having low shear strength has been increasing.

Therefore, the present invention has an object to simplify the test apparatus and increase the number of samples.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, there is provided a frame which straddles a test body, a vertical pressing means which is attached to the frame downward, and which is attached to the frame substantially horizontally. A simple rock shear tester is constituted by the shear direction pressing means.

(Action) The rock is cut into blocks in advance, shaped and made into test specimens, and anchor bolts are buried on both sides of this test specimen.
The frame of the test apparatus is fixed with these anchor bolts.

Next, while holding the test specimen downward with the vertical pressing means,
The test specimen is pressed by the shearing direction pressing means and sheared.

The applied load at this time is measured by a load meter attached to each means.

To transport the test apparatus, the frame itself, the vertical pressing means and the shear pressing means are disassembled and transported manually.

(Example) An example of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a front view of a simplified rock shearing test apparatus according to the present invention, FIG. 2 is a view taken along the arrow II in FIG. 1, and FIG. 3 is a III view in FIG.
It is an arrow view.

The simple rock shearing test device 1 (hereinafter abbreviated as "shearing device 1") has a gate shape by connecting the upper ends of the legs 2b, 2b standing up from the base plates 2a, 2a (see FIG. 2) with a top beam 2c. The frame 2 has a hydraulic cylinder 11 and a load detector 12
And vertical pressing means 10 composed of an upper pressing portion 13 and, on the other hand, tie beams 3, 3, horizontally from the lower portions of the legs 2b, 2b.
3, 3 (see FIG. 3) are extended, and shear direction pressing means 20 including a hydraulic cylinder 21, a load detecting section 22, and a lateral pressing section 23 are attached to the tie beams 3..

The load detectors 12 and 22 are for continuously measuring the applied pressing force of the hydraulic cylinders 11 and 21, and include, for example, a ferromagnetic material built therein, and the ferromagnetic material is mechanically distorted. The magnetization characteristics change in response to the change, and this change is converted into a current and output to the outside.

The upper pressing portion 13 and the lateral pressing portion 23 have rollers 13a and 23a at their ends, respectively, and convert the pressing force into a distributed load.

Note that the leg member 2b and the top beam 2c are removably coupled with bolts and nuts BN1, and the leg member 2b and the tie beam 3 are removably coupled with bolts and nuts BN2 so that the frame 2 can be carried by hand. Further, the other end of the tie beam 3 is removably connected with a bolt and a nut BN3.

 The operation of the shearing device having the above configuration will be described below.

FIGS. 4 (a) to 4 (c) are explanatory views of cutting out a test piece,
As shown in FIG. 4 (a), the rock 31 was excavated, and
Cut out a block 32 of cm × 20cm × (height) 10cm. Excavation should be done with careful hand flea digging.

Next, as shown in FIG. 4 (b), a concrete form 37 is put on the block 32, concrete is poured into the block 32, and the concrete 33 is attached to the block 32 by a predetermined thickness.
The illustrated test body 34 is formed. Note that one side surface is an inclined surface 34a inclined by 15 ° with respect to the perpendicular.

Further, anchor bolts 35 are embedded on both sides of the block 32 (FIG. 4 (c)).

Next, as shown in FIG. 5 which is an operation explanatory view, the shearing device 1 of the present invention is brought in, the frame 2 of the shearing device 1 is put over the test body 34, and the base plates 2a, 2a (see FIG. Secure with nuts on 35 ...

Next, pressurized oil is supplied from a hydraulic pump unit (not shown) to the hydraulic cylinder 11 in FIG. 5, and the test body 34 is loaded with a constant vertical load by the upper pressing portion 13. The inclined surface 34a of 34 is gradually pressed to cause shear failure.

The vertical load N and the shear load T during this time and at the time of breaking are measured by a pen writing recorder 36, and various numerical values are obtained by the following formulas.

Shear stress τ = T cos θ / A Normal stress α = (N + T sin θ) / A where A is the area of the shear surface θ is 15 ゜ After one test, the bolt, nut BN1, BN2 and
Loosen BN3, frame 2, tie beam 3, hydraulic cylinder 1
Separate 1, 21 and transport them manually. Then, these are moved to the next specimen and assembled. Hereinafter, a shear test may be sequentially performed.

The present invention is also characterized in that anchor bolts are embedded. Since the anchor bolt is easy to construct, it may be constructed in parallel with the excavation and hand chisel excavation shown in FIG. 4 (a), and the curing of the anchor bolt mortar is the same as that of the concrete curing shown in FIG. 4 (b). There is no time loss because it may be performed in parallel, and small test specimens are manufactured in sequence and the shearing device can follow up, so that the total test time is greatly reduced.

The anchor bolt 35 is not limited to this, and may be replaced with an anchor fitting such as an anchor frame or an anchor that is embedded in the bedrock 31.

(Effect of the Invention) As described above, according to the present invention, a rock shear test is carried out with a portable shearing device in which a frame is fixed with anchor bolts and can be disassembled and assembled. Instead, the test was possible even in the open-air condition, so that the test work became easy, the number of samples could be doubled, and the shear strength of the rock mass could be calculated at a high level.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a simple rock shearing test apparatus according to the present invention, FIG. 2 is a view taken on line II of FIG. 1, FIG. 3 is a view taken on arrow III of FIG. 4 (a) to 4 (c) are explanatory diagrams of cutting out a test body, FIG. 5 is an explanatory diagram of an operation, and FIG. 6 is a diagram illustrating a conventional in-situ test. 1 ... simple rock shearing test device (shearing device) 2 ... frame 10 ... vertical pressing means 20 ... shearing pressing means 31 ... rock, 32 ... block 34 ... test piece, 35 ... anchor fittings

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-150613 (JP, A) JP-A 64-30432 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 3/00-3/62 G01N 33/24 E02D 1/00

Claims (1)

(57) [Claims] 1. A simple rock shear test apparatus for shearing and breaking a test body formed by cutting a rock to be tested into blocks in advance and shaping the rock, wherein the simple rock shear test apparatus straddles the test body. A frame to be arranged, an anchor for fixing the frame to the bedrock, a vertical pressing means mounted downward to the frame, and a shear pressing means mounted substantially horizontally to the frame. A simple rock shear test apparatus characterized in that it can be disassembled so that it can be transported.