RU2705851C1 - Method and device for determining friction forces and soil shear modulus in field conditions - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: invention relates to engineering and geological survey facilities and is intended for evaluation of soil properties by rotary cut in zones of proposed construction. Method for determining resistance of soil to rotary cut consists in immersion by swirling rock-breaking leading impeller, located on screw column, by means of power mechanism into soil to preset depth with further axial crushing and rotation according to a given program by a given angle with measurement of torque, axial force, rotation angle and vertical movement. Force factors are measured by sensors arranged on a single power base in a lower hollow link of a screw column carrying an impeller. Signal transmission to control computer via wireless communication is performed continuously during testing, as well as data transfer along vertical movement and turning angle of impeller and processed in real time using programs based on known solutions of soil mechanics and theory of elasticity.

EFFECT: high accuracy of measurements of power parameters, reduction thereof in a single control center and calculation of characteristics of soils in real time mode, high mechanical capabilities and volume of measured parameters taken during one drilling.

6 cl, 1 dwg

Description

The proposed method for determining the strength and deformation properties of soils and a device for its implementation relate to engineering and geological surveys and can be used to assess the resistance of soils to rotational shear in areas of the proposed construction.

Known methods and devices for assessing the properties of soils under static tool pressure [1], with shear deformations [2]. In this case, a complex load is not created and, therefore, there is no reliable information on the shear properties of the soil.

Known [3] is a method of testing soil for shear, which consists in screwing into the soil a joint column of external and internal rods with the possibility of their relative rotation. At a given depth, the inner rod is rotated from a calibrated spring, providing a cut of a portion of the soil with recording of the torque transmitted from the power drive.

The disadvantage of this method is the significant error in the measurement of torque due to the mutual friction of the pipe columns and the limited depth of immersion.

A close analogue of the proposed method essentially solved the problem is a method for assessing the mechanical properties of the soil described in [4]. With this method and device, the leading impeller mounted on the hollow column of the rods is immersed in the ground using the power mechanism to a predetermined depth, a rotary cut is performed with the signal from the torque sensor being fixed by the recording unit during the cut process. When crushing to the next depth, the process repeats. The limited test depth without preliminary drilling and the lack of accuracy in measuring force factors are the disadvantages of this method.

The closest prototype of the proposed method and device is a method for determining soil resistance to a rotational cut and a device for its implementation [5].

This method includes the following actions: introducing by screwing the leading rod mounted on the screw column the impeller into the test soil using the power mechanism to a predetermined depth, vertical crushing and cutting of the soil with measurement of torque and angle of rotation using the recorder built into the hollow lower compartment of the rod. After reversing the rotation of the column, drilling is carried out to the next predetermined level with the repetition of actions. At the end of the test cycle, the recorder is recessed and the obtained parameters are read.

The disadvantages of the described method are the lack of accuracy in measuring the pressure of the indentation, the inability to obtain the calculated soil characteristics in real time, the lack of data on the temperature and acceleration of soil vibrations in the test zone.

The prototype device consists of a rig mounted on the triggers as a power mechanism, interacting with a screw column of rods, equipped with a rock-cutting lead impeller at the bottom, connected to the column through a hollow end compartment, in which the torque sensor and the recorder are located, the readings from which are taken after extraction rods. The rotation angle and vertical force are measured by external sensors.

The disadvantages of this device are the low accuracy of providing power factors when crushing and turning the impeller, the limited immersion depth, the need to remove the bar for taking results, and the lack of a single center that processes all incoming measurement data.

The technical problem of the proposed method and device is to increase the accuracy of the measurements of power parameters, bring them into a single control center and calculate the characteristics of soils in real time, increase the mechanical capabilities and the volume of measured parameters taken during one drilling.

The solution of the technical problem posed in part of the method is achieved by the fact that using the drilling rig mounted on the triggers, the leading impeller located at the end of the screw column of the rods is caught and rotated in the soil with the application of axial force and torque measured by the sensor, at a given depth: measuring the angle of rotation of the impeller, measuring the force of crushing the impeller, soil temperature, acceleration of soil vibrations, while the computer connected to the control panel is programmed on the basis of eny soil mechanics and the theory of elasticity calculates the characteristics of the ground in real time. For example, shear modulus, Poisson's ratio, undrained soil strength, etc.

The following changes are made to the device part. To reliably and more accurately study the properties of soils, the screw column is immersed to a predetermined depth, and then, using the servo located on the top in the lower hollow compartment of the screw column, the impeller is vertically trapped in the soil below the bottom of the borehole, and the soil is cut with a second lower positioning servo by rotating the impeller with a predetermined rotation speed. The program for testing and processing the results is embedded in the control computer, which receives wireless signals from the recorder located in the lower hollow compartment of the screw string, as well as the axial force and torque sensor located on the same power base. A thermocouple, a three-axis accelerometer, an amplifier of signals from sensors and an analog-to-digital converter, which are part of the recorder, a power supply unit and a transmitting antenna, are installed in the same hollow link of the screw string. To increase the resource, the impeller is equipped with carbide teeth.

The proposed procedure for assessing the resistance of soil to rotational shear and the changes introduced into the device allow:

- with great accuracy, using two servos to vertically crush the impeller and rotate it due to their location in the lower hollow compartment of the screw string;

- due to the contactless communication of the recorder with the control computer, transmit measured parameters instantly and carry out lengthy tests without lifting the column;

- due to the program for processing all parameters introduced into the computer (axial force, torque, angle of rotation of the impeller, vertical movement of the screw string, temperature, angle of deviation of the screw string from the vertical, acceleration of oscillations), based on the well-known decisions of soil mechanics, to obtain soil characteristics in real time time;

- to increase the resource of the impeller due to the modernization of its design by introducing carbide teeth;

- take into account the actual temperature of the soil in the study area due to the installation of a thermocouple in the lower hollow compartment of the screw string;

- measure the angle of inclination of the screw columns, the speed of longitudinal and transverse waves due to the installation of a three-coordinate accelerometer in the lower hollow compartment of the column of screws.

The device diagram is shown in FIG. one.

Implementation of the proposed method using the developed device is as follows. The drilling rig [1] provides the introduction into the soil of a screw column with a lower hollow link [2], bearing a rock-cutting impeller equipped with teeth [3] below. An axial force and torque sensor [4], a servo drive [5], a thermocouple and a three-axis accelerometer [6], a recorder [7] connected through a transmitting antenna [8] to a receiving antenna [9] of the control are mounted in this hollow link on a single power base and a processing computer [10]. When the drilling rig reaches the specified depth (without reaching the height of the impeller to the place of investigation), the servo drive [5] is turned on, which, when measuring the depth by the displacement sensor [11], presses the impeller to a predetermined depth with measuring the pressure of the crushing force by the sensor [4]. After that, the servo-driver [5] provides left-handed rotation and cutting of the soil with a given rotation speed and measurement of sensing parameters of torque, rotation speed, soil temperature, angle of deviation of the screw column from the vertical, the speed of transverse and longitudinal waves in the area of the head compartment of the screw column.

After taking measurements at a given depth, the column is lowered to the next level with repeating the operation to measure the sounding parameters. Using their computer in real time, at the end of each stage of measurement, it gives the calculated characteristics of the soil.

The advantages of the proposed method and device for its implementation are the reliability and accuracy of the measured parameters, the long service life without lifting the column up, the speed of obtaining design characteristics in a wider range, which allows a comprehensive assessment of the properties of soils in the study area.

The proposed method and device are significantly different from the known ones, they quickly, widely and reliably solve the problem of assessing the properties of soils, meet the requirements of modern engineering and technology, can be used in engineering surveys and, according to the authors, can be protected by a RF patent.

Information sources

1. USSR copyright certificate No. 1019054, M, class. E 02 D1 / 00 dated 1983

2. USSR copyright certificate No. 1214839, M, class. E02 D1 / 00 from 1982

3. Copyright certificate of the USSR No. 276472, M class. G0 11 1/00 from 1970

4. Copyright certificate of the USSR No. 1726643, M class. E 02 D1 / 00 from 1992

5. RF patent RU 2295606, C1E02 D 1/00 from 2005

Claims (6)

1. The method of determining soil resistance to a rotational cut consists in immersion by screwing a rock-cutting leading impeller located on a screw column using a power mechanism into the soil to a predetermined depth with further axial crushing and turning according to a given program at a given angle with measurement of torque, axial force, angle of rotation and vertical movement, characterized in that the measurement of force factors is carried out by sensors located on a single power base in the lower hollow link of the auger a column supporting the impeller, and the signal is transmitted to the control computer wirelessly continuously during the tests, as well as the data on the vertical movement and the angle of rotation of the impeller and is processed in real time using programs based on well-known solutions of soil mechanics and theory elasticity. 2. The method according to claim 1, characterized in that the temperature and acceleration of soil vibrations are measured using thermocouples and a three-axis accelerometer built into the lower hollow link of the screw column. 3. A device for determining soil resistance to a rotational cut, consisting of a rotation mechanism in the form of a drilling rig set up on triggers, with a screw column ending in a leading rock cutting impeller mounted on the lower hollow link of the screw column, characterized in that they are mounted in the hollow link of the screw column axial force and torque sensor, impeller angle sensor, thermocouple, three-axis accelerometer, power supply and recorder with antenna connected to a single power base anny radio communication with the antenna control computer, which receives signals from the recorder. 4. The device according to p. 3, characterized in that the axial crushing and circular cut is performed using a servo drive installed in the lower hollow link of the screw column of the rods. 5. The device according to p. 3, characterized in that the installation is equipped with a control computer that calculates the characteristics of the investigated soil in real time. 6. The device according to p. 3, characterized in that the impeller has the shape of a four-blade chisel with teeth.

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