JPS6254927B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for directly testing the shear force of the ground on-site.

Conventionally, direct on-site shear tests have been conducted to determine the shear strength of the ground, where it is difficult to sample the desired land. The procedure for this test is to cut out a portion of the specimen (see Figure 1) from the desired ground, cover it with a shear box, apply vertical pressure A through the pressure plate, and apply shear force B from the side of the box. In addition, shearing occurs between the ground and the bottom surface 2 of the specimen. (See Figure 2) This test method had the drawback that the specimen 1 or the shear box tilted due to shearing. (Second
In other words, since the shear force is applied above the shear plane 2, a moment acts on the specimen 1, which tilts the specimen. If the point of application of the shear force is placed at the bottom of the shear box, theoretically no moment will work, but the actual shear plane will not occur at the bottom of the shear box, but will occur at a point that is slightly shifted from the bottom of the shear box.
It is not possible to eliminate the instability caused by tilting the specimen 1. In addition, the pressure plate that applies vertical loads and the shear box are not fixedly integrated, so when shear force is applied to the specimen from the side of the shear box, the side being pushed rises and the pressure plate is tilted, or the edges From then on, it began to show signs of strong progressive destruction.

Direct shearing is a test in which shearing force is applied from the upper and lower pressure plates of the specimen, and the deformation that shifts the upper and lower surfaces 2 and 3 of the specimen 1 in parallel is specified, so the shear force B and vertical pressure A applied to the specimen are specified. must be added in such a way as to cause the desired deformation.

The present invention was developed in view of the above matters, and
It is an object of the present invention to provide a method and device that allows a force couple to act in the vertical direction on the upper surface of a specimen, and that is simpler than conventional methods and that can accurately determine the shear force of the desired ground. That is.

Next, embodiments of the present invention will be described based on the drawings.

A specimen 1 of a certain size is cut out at a desired position, a flat plate 4 is placed around the bottom surface 2 of the specimen 1 at a slight interval, and the peripheral wall 6 of the shear box 5 is attached to the specimen 1. A spacer 7 is interposed between the bottom of the peripheral wall 6 and the flat plate 4 or the ground 17, and if there is a gap between the peripheral wall 6 and the specimen 1, the gap is filled with coarse sand 8. This is to improve the fit between the peripheral wall 6 and the specimen 1. For this reason, a thin layer of coarse sand 8 or fine gravel is spread on the upper surface 3 of the specimen 1, and a pressure plate 9 is placed on top of it. Place. Next, an appropriate number of round rods 10 are held and placed on the holder 11 parallel to the surface on which shearing force is applied to the upper surface of the pressure plate 9, and the backing plate 12 is installed on top of the round rods 10, and the base rods are placed on top of the round rods 10. A pressurizer 14 for applying vertical pressure to the specimen 1, a weight meter 15, and a vertical displacement meter 16 for reading vertical changes are installed in the center of the upper surface of the base rod 13, and the upper surface of the specimen 1 is always One side of the base rod 13 is attached to both ends of the base rod 13 so that it forms a horizontal surface.
On the other side, a couple generating device such as an air cylinder or a hydraulic jack 18 is installed between the base rod 13 and the ground 17 on the upper surface, and a level is provided on the base rod 13 to know the horizontal state of the base rod 13. A vertical column 21 is provided with a container 19, etc., and is always held in a fixed position by deployable anchors 20, which are opened and closed in two by four hydraulic pressures, at the upper end of the pressurizer 14.
The one jack 18 is installed between the base rod 13 and the vertical column 21, and the one jack 18 is installed between the base rod 13 and the vertical wall 6 of the shear box 5.
Pressurizer 22 that applies shear force to one side, weight meter 2
3 and a horizontal displacement meter 24 for monitoring the shear displacement, the pressurizer 14 is activated first, and the specimen 1
Vertical pressure A is applied to the area, and when the consolidation operation is completed, the pressure plate 9 is fixed to the peripheral wall 6 of the shear box 5 by tightening nuts, etc., and the connection between the peripheral wall 6 and the ground 17 or the flat plate 4 is fixed. The spacer 7 interposed therebetween is removed, and then the pressurizer 22 provided on one side of the peripheral wall 6 is operated to apply shear force B to the specimen 1. At this time, a moment acts on the upper surface 3 of the specimen 1 in such a way that the pressed surface tends to lift upwards.The above-mentioned force generating device is activated to generate a couple that is opposite to the moment, and the specimen is moved upward. In this way, the shear force of the specimen 1 is measured by keeping the upper surface 3 of the specimen 1 always in a horizontal plane. As shown in Fig. 5, the anchor 20 is constructed by connecting semi-cylindrical cylinders 31 and 32 with tension springs 28 and 29 and a hinge 27, which can be opened and closed by a hydraulic cylinder 26, and 30 is a slider. 25 is a reaction rod with a threaded portion provided at the top, and 33 is an oil feed pipe.

Since the present invention has the above-described method and configuration, it is possible to inspect and measure the desired ground shear force extremely accurately despite having an extremely simple configuration, and is easy to operate and handle. etc,
This effect has an extremely wide range of applications.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a specimen of the present invention, Fig. 2 is a principle diagram of an on-site direct shear test, Fig. 3 is an explanatory front view showing an embodiment of the present invention, and Fig. 4 is also an explanatory view. A side view, and FIG. 5 is an enlarged longitudinal sectional view of the anchor used in the present invention. 1...Specimen, 3...Top surface, 5...Shear box,
9... Pressure plate, 13... Base rod, 14... Pressure device,
17...ground, 18...air cylinder or hydraulic jack, 20...anchor, 21...vertical, 22...pressurizer.

Claims (1)

[Claims] 1. Cut a specimen of a certain size at a desired ground site, cover the specimen with a shear box, and apply a vertical load to the specimen through a pressure plate. When the consolidation is completed, the pressure plate is fixed to the peripheral wall of the shear box, and then a shear force is applied to the specimen through the peripheral wall, and a couple force is applied to the specimen through the pressure plate to cancel the moment generated by the force. and give it to the specimen,
A method for direct on-site shear testing of the ground, characterized in that the upper surface of the specimen is always held horizontally. 2. At the site of the desired ground, a shear box with a pressure plate that can be placed on the top surface of the specimen to be cut to a certain size is installed so as to cover the specimen, and the shear box is placed at an appropriate distance from the specimen. Four deployable anchors were fixed to the ground on all four sides, and a vertical beam supported by these anchors was installed above the specimen, and the base beam was placed on a pressure plate parallel to the vertical beam. At one end of the base rod, an air cylinder or a hydraulic jack is installed between the base rod and the vertical floor, and at the other end between the base rod and the ground, an air cylinder or hydraulic jack is installed, and the base rod is A couple generator was constructed so that it could be held horizontally at all times on the pressure plate, and a pressurizer that applied a vertical load to the specimen was fixed to the base rod and installed between the base rod and the vertical support. , and a direct on-site shear testing device for the ground, characterized in that it is further equipped with a pressurizer that applies shear force to the specimen from one side of the specimen through a shear box.