SU1449864A1 - Method and apparatus for investigating compaction of grounds - Google Patents

Abstract

The invention relates to the study of physical and mechanical properties. soils and can be used in laboratory determinations of their density. The purpose of the invention is to increase the research efficiency by simulating and taking into account the compression of the underlying layer and its effect on the compaction of the top layer of the dirt embankment. To do this, when vibrating compaction of a soil sample with a certain number of shock pulses (n), it is moved in the direction of reaching the front of the forward wave of a shock pulse (L

Description

The invention relates to construction, to the study of the physicomechanical properties of soils and to determine the density of the soil t laboratory conditions.

The purpose of the invention is to increase the efficiency of research by simulating and taking into account the compression of the underlying layer and its effect on the compaction of the upper layer of the earth embankment.

On. The drawing is a diagram of the device, p; l implementation of the proposed method.

The device contains a vibration stamp 1 (for example, an electromagnetic one), a cylindrical glass 2 for sample 3 of the soil, fixed on the body of the hydraulic cushion 4., and the lower strain 5, which is rigidly connected by rods to the piston b 4 of the magnetic cushion 4 having the choke 7. Piston 6 is connected to the piston rod 8 of the discharge chamber 9. The hydraulic pad 4 and the chamber 9 are connected to the external hydraulic system of the maya. The device is equipped with a high voltage unit. Contains a high-voltage rectifier 10, connected to an external circuit, a variable capacitor 11, a switch 12 and a multi-wired amplifier 13.

The stamp 5 is mounted to a massdose 14 connected via an amplifier 13 to a switch 2 and an oscilloscope 18. In the discharge chamber 9 electrodes 15 are placed connected to a variable capacitor 11. The device also contains a displacement sensor 16 (for example, inductive), a lower stamp 5 and a sensor 17 sediment (for example, inductive) soil sample. Sensors 16 and 17 are connected via an amplifier 13 to an oscilloscope 18. The variable capacitor 11 engine has a mechanical flexible coupling 19 with a piston rod 6 of a hydraulic cushion 4, which is installed on spring dampers 20 with a resonant frequency of 150 - 200 Hz.

The method is carried out as follows.

The soil is poured into the cylindrical cup 2 and compacted by applying shock pulses through vibrating stamps 1. During the compaction process, the soil sample is moved in the direction of the front of the shock wave and the pulse at its approach to the bottom of the sample, which is determined by the increase in pressure on it the bottom end, which is measured using a massdose 14. The amount of movement of the soil sample (L) is given by the formula

 ABOUT)

average contact pressure in a compacted soil sample under the action of vibration where

f

Noise load: С (0,9 - 1,0) GP, MPa; ultimate strength of soil, MPa;

h - the height of the packed bed embankment in field conditions is taken depending on the characteristics of the vibrating machines, m; n is the number of shock pulses during the test; modulus of soil deformation, MPa (G p and EO, determined by known methods). Compaction is carried out until the sedimentation of sample 3 of the soil in a cylindrical cup 2 is stabilized. The density of the soil after stabilization of the precipitation is maximum for a given level of shock pulse (contact pressure), frequency, and number of pulses. In the final stage of compaction, when the sediment and the movement of the soil sample are stabilized, oscillations of the entire device begin to occur on the spring dampers 20, the resonant frequency of which is chosen equal to the resonant frequency of the soil.

Example. The magnitude of the displacement of the soil sample is calculated in the following way. Sand is compacted using a medium-capacity vibratory roller, such as SVAW-8. Pulse frequency f 25 Hz; About 0.2 MPa; , 7m EL 10 MPa. The total number of skating rink in one place 8; roller speed 0.6 m / s; the length of the zone to be compacted under the roller of the roller is 0.6 m.

The total number of pulses is

8 0.6

  about

25 200

0

five

0

Where

} maximum soil density. Then the offset value is

-five

 BUT

Ol2

m

200. 10 ° 7 ° ° The device operates as follows.

Vibrostamp 1 transmits vertical oscillations to sample 3 of the soil and compacts it in glass 2. At the moment the forward wave approaches, from the external shock pulse to the lower part of the soil sample of the meter 14, the pressure at the forward wave front is converted into an electrical signal that goes to the amplifier 13 and after amplifying and transforming its shape, it is used to control the operation of switch 12. Capacitor 11 is normally charged with a high-voltage rectifier 10. When the contacts of switch 12 are closed, the capacitance 12 ora 11 is transmitted

 through the electrodes 15 of the liquid (technical water) in chamber 9. An electrical breakdown of the fluid occurs, accompanied by the coincidence of the shock wave acting in the chamber 10-20 μs,

0 Under the action of a shock wave force, the piston 8 is lowered downwards and forces the piston 4 out of the body of the hydraulic cushion 4 by the piston 6 through the throttle 7. Simultaneously with the movement of the piston

5 6 there is a movement of the stamp 5 with the sample 3 of the soil. The sediment of the soil sample 3 relative to the body of the hydraulic cushion 4 is converted, respectively, into an electrical signal in sensors 17 and 16, the outputs of which are connected via an multichannel amplifier 13 to an oscilloscope 18, which during the test records pressure, displacement and precipitation over time. . The measurement results are used in determining the density of the soil by known formulas.

Q The amount of movement of the punch 5 with the sample 3 of the soil relative to the body of the hydraulic cushion 4 with one electric discharge in the chamber 9 is regulated by the volume of the fluid portion,

g ejected through the throttle 7. The volume of the fluid portion is determined by the distance inside the hydraulic cushion 4 and the size of the cross section of the throttling channel and is assigned depending

bridges of the magnitude of the movement of the soil sample under the action of a single I1-pulse, which is given by the formula

(one).

Since the deformation modulus E in the process of compaction of sandy EXP soil increases, mechanical bending connection 19 between the sensor 16 and the variable capacitor 1 is used in laboratory tests to take effect. When the die 5 moves relative to the body of the hydraulic cushion 4, the mechanical connection 19 acts on the variable capacitor engine 11, reducing its electrical capacity and the amount of stored energy. Reducing the energy of the electric discharge in chamber 9 leads to a decrease in the additional pressure on the piston 6 when the electrical discharge in the chamber 9. As the pressure of the liquid in the hydraulic pillow 4 decreases with each blow, the portions of fluid ejected through the throttle 7 TC is less and less at a certain pressure set by the parameters of the throttles. The use of such a reverse mechanical connection allows one to change the magnitude of the modulation of the strain Eg, practically according to any law of variation E, in field conditions.

The application of the method and device allows one to simulate and take into account when compacting a soil sample, compressing the p of the embankment layer or base layer and the effect of this compression on the compaction process of the upper layer of the pasa, which makes it possible to predict the required number of shock pulses to achieve a normalized density laboratory conditions and will use this data to designate the type of soil sealing technique, the layer thickness and the number of machine passes when compacting the soil in field conditions.

of

Reet e. n and

Claims (4)

1. A method for investigating the compaction of soils, including the filling of soil in a cylindrical cup; the application to it of the vibration load op; e M of the number of shock pulses, weighed down compacted soil and the determination of the density of f.; p, auls., O tl and h y and u with By the fact that, in order to increase the efficiency of research by simulating and taking into account the compression of the underlying layer and its influence on the compaction of the upper layer of the earth embankment, to- The pressure at the lower end of the specimen is measured, and when a vibratory load is applied, the soil sample is moved in the direction of the front of the forward wave of the shock pulse at the moment it approaches. .The lower part of the sample, which is determined by the program of increased pressure at its lower end, under-STOM, the soil sample is compacted until the sediment stabilizes, and the mixing value under the action of each shock pulse (i) is determined by the formula five  Dl G ,. 0 55 2p Eg  movement of the soil sample, according to the movement motion. forward wave front, m; average contact pressure in a compacted soil sample under the action of vibration loading-QC :; about. (0.9 - 1.0) b p (G p is the ultimate strength of the soil, Miia); V., - module of soil deformation, 3 Sha; n is the number of shock pulses during the test; ; h the height of the layer being compacted in field conditions, depending on the characteristics of the vibrating machines, m 2, A device for investigating soil compaction, including a cylindrical cup for stirring rpyi-iTa, vibration stamps with weights, and sensors for measuring ground settlement and vibration frequency, connected to an oscilloscope, in order to increase the efficiency of research by simulating and taking into account the compression of the supporting layer and its influence on the compaction of the upper layer of the dirt embankment, the device is equipped with a hydraulic sub-shaft, made in the form of a body with a crush and placed in a piston with rods running through Through a hole in the lid, which is connected to the cavity of the hydraulic cushion, a discharge canister with electrodes  . and a piston, a mesdose and a high voltage block, and the cylindrical cup is provided with a lower movable die with its displacement sensor and mounted on the lid of the hydraulic sink, the piston of which is connected by means of rods with the movable lower die of the cylindrical cup and the discharge piston of the discharge chamber, the high voltage unit is made in the form of a high voltage rectifier connected to an external circuit, a variable capacitor and a switch connected to the amplifier, and eight The discharge chamber electrodes are connected to a variable capacitor, and the massdose, mounted on the lower die, is connected through an amplifier to a switch and an oscilloscope. 3. The device according to claim 2, wherein the variable capacitor is mechanically coupled to one of the hydraulic cushion rods. 4. The device according to claim 2, about tl and - the fact that the body of the hydraulic cushion is installed on the spring dampers.