JPS59195992A - Measurement of strength and deformation characteristics of soil around boring hole - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention describes a method for measuring the strength and deformation characteristics of soil around a polling hole by strain control, and more specifically, a method for measuring the strength and deformation characteristics of soil around a polling hole, more specifically, by installing an inflatable measuring tube in the ground and inflating it to apply pressure to the ground. In addition, it relates to a method for measuring the strength and deformation characteristics of soil around a poling hole in a test (in-hole horizontal loading test) that obtains information such as the strength of the ground from the pressure and degree of expansion at that time.

Conventionally, in this test, a stress control method has been used in which the load is increased stepwise at a constant rate at intervals of, for example, 2 minutes. Figures 1(a) and 1(b) show the concept of the equipment for conducting the test. The gas pressure from the pressure source (gas cylinder) (1) passes through the pressure reducer (4) and reaches the volumetric meter (
2), and degassed water (3
) is pumped. The degassed water (3) sent to the measuring tube inflates the inner rubber tube (7) and applies pressure to the ground.

The pressure at this point is read by the ground pressure (5), the degree of expansion is read by the volume meter (2), and information such as the strength of the ground is obtained by a lenser etc. built into the measuring tube. . The rubber tube (7) on the outside of the measuring tube is inflated with gas pressure through a pressure reducer (6). Any load can be applied to the pressure reducer aQ in the figure by operating the regulator (4). This regulator is operated to add 1 (9) to any cart at 2-minute intervals.3 This method has an established analysis method tailored to its characteristics, and is widely used. It has greatly contributed to basic engineering with practical examples.

Further, FIG. 1(B) is similar to FIG. 1(A) except that the outer rubber tube is not used and therefore the pressure reducer (6) and the pressure gas circuit connected thereto are not provided.

However, with the recent development of soil mechanics, even more ground information has become necessary. The method of the present invention was developed to meet these demands.3゜The method of the present invention expands the measuring tube while keeping the expansion ratio constant. The gist of the present invention is to install an inflatable measuring tube in the ground, apply pressure to the ground by inflating it, and then measure the stress in the ground based on the pressure and degree of expansion. In the test method for obtaining information such as the strength of ゛, (a) a cylinder pump is used to pump water at a constant rate into the measuring tube to provide water pressure to inflate it, or conversely to drain water from the measuring tube; process, (b
) A process of controlling the water supply and drainage speeds and simultaneously recording the pressure of the measuring pipe, the pore water pressure of the ground around the measuring pipe, and the lateral deformation of the measuring pipe using an automatic control device and an automatic recording device, (C ) It includes the process of converting the water pressure of the measuring pipe into an electrical signal by the earth force sensor built into the measuring pipe without being affected by the head loss of the water sent from the cylinder pump to the measuring pipe.

The present invention will be demonstrated below by means of examples shown in the drawings.

In Fig. 2, (10) is a cylindrical pump, which contains 1:2 aerated water. At the same time that this water becomes a pressure medium, the degree of expansion of the measuring tube can be determined by measuring the change in its amount.

The screws 1 to 3 of the pump (10) are driven by a motor (8), and by keeping the rotation of this motor, and therefore the moving speed of the piston, constant, water injection into the pipe 11 is controlled.
! The temperature can be kept constant. The stress generated underground is determined by correcting the pressure generated inside the measuring tube. To measure the pressure at Illll direction +1111,
It can be found by measuring the pressure inside the cylinder pump (10) and correcting the difference in water head due to the height difference between the cylinder pump and the measuring pipe, but in reality (this is always cylinder pump < 10). Since a fixed amount of degassed water is discharged from the two, the pressure difference between the two is not only the head difference;
Therefore, such a method is not appropriate3. Therefore, in order to determine the pressure acting on the inside of the measuring tube, an electric pressure quadrant user (11) was built into the measuring tube.

By doing this, errors related to pressure horn measurement can be prevented.

Note that (13) is the metal cylinder of the measuring tube, and (12) is its rubber tube, which is inflated by pressure water from the pump (10). (9> is a pressure indicator that automatically records the pressure.

The advantages of the strain control method according to the invention compared to conventional stepwise control methods lie primarily in its test time.

In principle, in the horizontal hole loading test, loading is continued until a certain degree of expansion is reached. In the case of the conventional method, an attempt is made to cover the test opening as much as possible regardless of the strength of the ground by increasing the load increment if the ground is strong or reducing it if it is weak. There is. This is because setting a constant test time is extremely important from an engineering perspective in determining the ground conditions under load. However, since the strength of the ground is unknown before the test is carried out, the above method is not very appropriate in practice. In the case of the strain control method, the expansion rate is known, so the time required to reach a desired expansion is known in advance.
Furthermore, by adjusting the expansion rate, the time required to reach a desired degree of expansion can be freely set. Therefore, the strength of the ground is 'JIj! A fixed time-C test can be carried out in relation to this.

In the case of a dry land board, it is engineeringly meaningful to make this test G5B relatively short time, and it is a non-drainage row. , the results can clarify the conditions under ``undrained conditions'' and provide important engineering information. Met.

In the case of the conventional method, in order to load the cart in stages at 2-minute intervals, the load is maintained at the same level for 2 minutes (the moment when the load is increased and the time when the cart is placed on the ground is Strictly speaking, the state in which the deformation occurs is !5!I!.In the case of the strain control η of the present invention, the deformation is forced to occur continuously at the same speed. Due to these differences, there are differences in the 1q results, and as shown in Figure 3, a peak intensity occurs where the strain is small.This peak intensity is based on the engineering is significant 4f information. (14) is the peak intensity part, and (15) is the residual intensity part.

In the case of conventional load control methods, since the load increase rl is predetermined, it is not possible to accurately determine the peak intensity, and after reaching the peak intensity, the A deformation called shear failure occurs, and in this state it is impossible to measure the strength called residual strength that occurs underground.

However, since the strain control method of the present invention uses the lifting platform and the test is always conducted at the same deformation rate throughout the test, it is possible to determine the residual strength (under the shear plane failure) after reaching the peak. The difference is shown in Figure 3.

As mentioned above, the in-hole horizontal loading test using the strain control method of the present invention is a test method with complicated characteristics.

[Brief explanation of the drawing]

Figure 1 (a) and (b) are illustrative diagrams showing the horizontal loading test in the hole using the conventional stepwise load control method, and Figure 2 is an illustrative diagram showing the horizontal loading test in the borehole using the strain control method of the present invention. , FIG. 3 is a comparison chart of ground information obtained by the conventional method and the method of the present invention. 8,...Motor 9,...Pressure indicator 10,...
・・・・・・Cylinder pump 11,・・・・・・・・・
・1 Mocha Transduly--12,・・・・・・・・・
・Rubber duplex 13,...Metallic cylinder 14,...Peak strength section 15,...
......In Figure 3 for the residual strength section■ ......Stepwise load TR measurement method (conventional method)
・・・・・・・・・・Strain control method (method of the present invention) 11 Fig. 1 Fig. 1 Fig. 2 Fig. 3 ε6 in%

Claims (1)

[Claims] (1) In test method 1, an inflatable measuring tube is installed in the ground, and the tube is inflated to apply pressure to the ground. At that time, information such as the strength of the ground is obtained from the pressure and degree of expansion. a
(b) using a cylinder pump to pump water at a constant rate to give water pressure to the measuring tube to inflate it, or conversely to drain water from the measuring tube; (b) using an automatic control device and an automatic recording device; In addition to controlling the water supply and drainage speeds mentioned above, the pressure of the measuring pipe and the pore water pressure of the ground around the measuring pipe d3
(C) The pressure sensor built into the measuring tube simultaneously records the measurement tube's lateral deformation. A method for measuring the strength and deformation characteristics of soil around a poling hole using a strain control method characterized by including the process of converting water pressure into an electrical signal.