SU846637A1 - Device for measuring shear resistance of soils and loose materials - Google Patents

Description

(54) DEVICE FOR RESEARCHING THE RESISTANCE TO SHIFT OF GROUNDS AND FILLING MATERIALS The invention relates to the study of the physicomechanical properties of soils and bulk materials, namely to the study of shear resistance. A device is known for investigating plane shear of soils and bulk materials, including upper and lower clips, devices for creating and measuring normal and shear forces III. The closest to the proposed technical entity is a device comprising an upper matrix, a lower matrix installed on a sliding cart, a piston, devices for creating and measuring shear forces, devices for creating and measuring the force applied to the piston, a sensor for moving the lower matrix G2L. The device has insufficient accuracy in measuring the force perpendicular to the shear plane and is assumed to be equal to the force applied to the piston. It does not take into account that the force perpendicular to the shear plane is less than the force applied to the piston by the amount of friction forces. The purpose of the invention is to improve the accuracy of the study. This goal is achieved by the fact that the device for examining the resistance of the soil, containing the upper and lower matrices, the piston is installed at the top and the bottom is placed on the cart of the device associated with the matrices for creating and measuring normal and shear loads, equipped with an additional pressure indicator and a force meter associated with the upper die and the piston. Moreover, the load cell is made in the form of two rods with electrogenometric sensors pasted on them, and the upper matrix is made with flanges and screws that are installed in the threaded holes of the flange and supported in the load cell. At the same time, the friction forces of the test material and the piston against the walls of the upper matrix are transmitted to the load cell and can be measured. In this case, the force perpendicular to the shear plane is determined by the forgmule

where F is the force perpendicular

shear planes; f - force applied to the piston; FT - FORCES of the test subject

material and piston on the walls: ki upper matrix.

Thus, the previously unrecognized rubbing forces of the tested material and the piston against the walls of the upper matrix in the proposed device can be measured and taken into account when determining the forces perpendicular to the shear plane. This makes it possible to increase the accuracy of the shear resistance analysis.

FIG. 1 shows the device, a general view; in fig. 2 - bottom matrix with a dolly, a sensor for detecting the movement of the lower matrix, a device for creating and measuring shear stress.

The device works as follows. The device is mounted on the base plate 1 and contains the lower matrix 2 mounted on the carriage 3, the upper matrix 4 with the flange 5, which is mounted to the force-measuring device 6, for example, consisting of two pins with electrosensory sensors. To adjust the gap between the lower matrix 2 and the upper matrix 4 in the threaded holes of the flange 5 are installed screws 7, abutting the load cell 6. To prevent the upper matrix 4 from tilting, the sleeves 8 are sliding to the flange 5, sliding along the guide posts 9. Is The material 10 is compressed by piston 11. The force on piston 11 is created by screw 12 and measured by a compression dynamometer 13. The shearing force is generated, for example, by weights 14 suspended on cable 15 passing through roller 16.g Shear force is measured by sensor 17 which is attached This is the bottom matrix 2. The arrangement of the string 18 must be such that the line of action of the shear force lies in the shear plane. To register the movement of the lower matrix 2 to the base plate 1. A micrometer indicator of the hour dial type 19 is attached.

Shear resistance studies on the proposed instrument are conducted in the following sequence.

Check the installation of the support PLIC 1, which must be installed firmly and horizontally. The horizontality of plate 1 is checked with a level. A check is made before each study. The cart 3 is set so that the axes of the lower matrix 2 and the upper matrix 4 coincide. The screws 7 are unscrewed until the upper matrix 4 is lowered by 1 and 2, which are filled with the research material.

The piston 11 is installed, the diameter 13 and the rotation of the screw 12 create a force on the piston 11. A micrometer indicator of the clock type 19 is installed to register the movement of the matrix 2. The shear force sensor 17 is connected to the tension bar 18, the cable 15 is guided into the groove of the roller 16 and is attached Shear force 17. The gap between the upper die 4 and the lower die 2 is set by moving the upper die 4 with the flange 5 and the sleeves 8 in the guides 9 by simultaneously rotating the screws 7 until it stops with the load cell 6. By successively increasing the weight of the weights 14, the lower matrix 2 is shifted with the trolley 3 relative to the upper matrix 4. The displacement of the matrix 2 is recorded by indicator 19. A shift is considered to have occurred if, without increasing the weight of the weights 14, a continuous increase in the rate of shear deformation occurs.

During shear, the vertical force F applied to the piston 11 by the dynamometer 13, the frictional force Fj of the material under study 10 and the piston 11 against the walls of the upper matrix 4 are recorded, which are transmitted through the flange 5 and the screws 7 to the load cell 6 by the shear force sensor F-17. The force perpendicular to the shear plane is determined by the formula

  1 - b

where F is the force applied to the piston 11; F- - strength of friction investigated

mothers C1La 10 and piston 11 against the walls of the upper matrix 4j F — force perpendicular to the shear plane. The average stress normal to the shear plane is determined by

. 4- F-1 according to the formula 3 g where rf is the inner diameter of the lower and upper

matrices. Average shear stress

g 4-F-1

0 is determined by the formula 6- .-,

tg- About

where RD - the shear force recorded by the sensor 17.

After conducting a series of shear tests, a graph (t) is constructed, which characterizes the shear resistance of the material under study at various values of the voltage normal to the shear plane.

The use of the invention makes it possible to increase the accuracy of investigating the similarity of displacements of soils and bulk materials, which is of paramount importance for practice, since it determines the accuracy of innational calculations by definition

Claims (3)

Claim A device for studying the resistance to shear of soils and bulk materials, containing the upper and lower matrices, with a piston installed in the upper one and a lower one placed on a trolley, devices associated with the matrices ..15 for creating and measuring normal and shear loads, characterized in that, with studies to improve accuracy, it is provided with a separate pressure indicator and siloizmeritolem _l associated with the upper die and the piston. 2. The device according to claim 1, characterized in that the silo-damper is made in the form of two rods with electrotensometric sensors glued to them. 3. The device according to nnl and 2, characterized in that the upper matrix is made with a flange and screws that are installed in the threaded holes of the flange and are supported by a load meter.