RU2555529C2 - Method of compressibility test of porous material environment and device for its implementation - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: invention relates to the field of "Physics of the material contact interaction" of hard flat body with a porous material environment, and is intended to determine its parameters of deformability and strength. Essence: the material environment is loaded with rigid flat perforated stamp with stepwise increasing load until the moment of loss of bearing capacity of the environment and sustainability of the stamp on it. The parameters of pressure p_i and deformation S_i of the environment at loading are controlled in time and a graph of test is plotted, by which the parameters of strength and deformability of the environment are determined. Each stage of deformation of the environment is kept constant in time to its conditional stabilization. Before setting the next steps of the deformation of the environment the elastic load cell is fixed with a locking screw of the load device. The device consists of a housing with a working chamber, fixedly mounted on the bottom of the chamber of the lower rigid flat perforated stamp, the working ring with a sample of the material environment, installed in the upper part of the working ring on the sample of the environment of the upper rigid flat movable perforated stamp and the loading device. The loading device consists of a rigid frame with an upper and lower beams and two guide racks, a pusher and a resilient load cell.

EFFECT: increased productivity of test of the environment on compressibility and strength.

2 cl, 2 dwg

Description

The invention relates to the field of “Physics of Material Contact Interaction” of a rigid flat body with a porous material medium and is intended to determine its deformability and strength parameters.

Known dynamometric method S.S. Vyalov’s determination of the long-term strength of a frozen material medium under conditions of free lateral expansion and, if it is not possible, in odometers, namely, that a one-time load is applied to the sample of the medium through a stamp, slightly less than the temporary compressive strength, the deformation λ _{01 of a} spring or a standard dynamometer installed between the sample medium and the die, and the initial deformation λ of the sample ₀₂ environment, kept in a compressed sample time t of the medium during the relaxation of stresses in it when decompressed pruzhi s dynamometer and decrease deformation of the sample is measured by the increasing deformation of the test sample medium to its final stabilized value, determine compressive strength σ _dm ≈P _κ / F, where P _κ - long-term strength test medium, F - stamp contact area with the sample and precipitation S _i medium in a frozen state and thawed, as well as elasticity modulus E _Ex frozen medium [1].

A dynamometric method for testing a sample of a material medium for compressibility during stress relaxation in it allows one to obtain only the elastic modulus of strong and frozen media. It does not allow one to determine the general deformation modulus of a frozen and ordinary less durable porous, highly compressible medium in the samples and by the depth of the material array being tested, when it is necessary to create several stages of stamp loading while fixing the stabilized stress-strain state of the sample under an initially specified load.

The closest in technical essence to the proposed is a method of testing a porous material medium with static loads, which consists in loading the prepared surface of the test medium through a rigid flat stamp with stepwise increasing static loads corresponding to pressure steps P _i until the medium has lost its carrying capacity and stability stamp, while each stage of loading the medium with a static load is maintained in time until a conditionally accepted stabilizer tion precipitation medium S _i, the results of trials plotted S _i = ƒ (p _i) and is determined according to the schedule parameters of strength and deformability of the test medium [2].

A significant disadvantage of the known method of testing a porous material medium is the long duration and cost of carrying it out, associated with a significant waiting time for stabilization of the sediment under load under the conditions of their fixation and conditionally accepted stabilization of the precipitation of the medium in time at each test stage.

The technical result according to the relaxometric method of compressibility testing of a porous material medium, namely, that the prepared surface of the material medium is loaded with a rigid flat perforated stamp in a stepwise increasing static load stabilized in time t until the medium is lost and the stamp is stable on it, the parameters are controlled in time pressure p _i and the corresponding deformations S _{i of the} medium at each increasing stage of loading, build a test schedule with are rare in its conditionally stabilized at each loading stage p _i = ƒ (S _i ), according to the graph, the parameters of the medium strength and deformability are determined, it is achieved by the fact that at the initial and each subsequent increasing stage of medium loading with a stamp, a stepwise increasing medium deformation through elastic the dynamometer element, each increasing stage of deformation of the medium is maintained constant in time until it is conditionally stabilized during stress relaxation in it and pressure p _i stabilizes under the stamp, while Before defining subsequent stages of medium deformation, the elastic dynamometer element is fixed from deformation by the locking screw of the load device.

The proposed relaxometric method for compressibility testing of a porous material medium accelerates stamp tests tenfold.

A device for testing the compressibility and strength of a material medium, which contains a housing with a bottom, a working chamber for compression testing of the medium, a working ring, upper and lower perforated dies, a meter of deformation of the medium in the working chamber, a load device in the form of a compression spring, connected through a rigid a frame with rungs and through a pusher in the form of a loading bolt with a ball bearing with an upper stamp, and a compression spring is installed between the bottom of the housing and the lower rung of the frame [3].

The known design of the compression device does not allow the creation of the same sample of the material medium, increasing stages of deformation without a device for braking the deformation of the compression spring and without rebooting.

The technical result of a device for compressibility testing of a porous material medium, consisting of a housing with a working chamber, fixedly mounted on the bottom of the chamber of the lower rigid flat perforated stamp, a working ring with a sample of the material medium installed in the upper part of the working ring on a medium sample of the upper movable rigid flat perforated stamp, load device, is achieved by the fact that the load device consists of a rigid frame with upper and lower rungs and two on leveling racks, movably mounted in the vertical guide bushings of the housing, a pusher rigidly connected to the upper crossbeam of the frame and abutting through the ball against the stop of the upper stamp, an elastic dynamometer installed between the housing and the lower crossbeam of the frame and resting through the glass and the thrust bearing in the screw stop of the lower the crossbar of the frame, and the movable stamp is made with a lock of its movements and compression of the material medium, the clamp of the stamp is made in the form of a stop screw ator movable die.

The invention is illustrated by graphic materials, where in FIG. 1 shows a general view of a compressiometer with a sample of the material medium; FIG. 2 - graphs e _i = ƒ (p _i , t _i ) of the compression test of the medium in the mode of specified deformations and relaxing load, combined with the graph e _i = ƒ (p _i ) of calibration of the compressiometer.

The compressiometer consists (Fig. 1) of a housing 1 with a cylindrical working chamber 2 installed in it at the bottom of the lower rigid flat perforated stamp 3 and a working ring 4 with a sample 5 of the material medium installed in the working ring on the sample of the upper perforated rigid flat stamp 6 s emphasis 7, load device 8, consisting of a rigid frame 9 with upper and lower rungs 10, 11 and two guide racks 12, movably mounted in vertical guide bushings 13 of the housing 1, pusher 14, is rigidly connected go with the upper crossbar 10 of the frame 9 and resting through the ball 15 against the stop 7 of the upper stamp 6, an elastic dynamometer element in the form of a compression spring 16 installed between the housing 1 and the lower crossbar 11 of the frame 9 and resting through the cup 17 and the thrust bearing 18 against the screw stop 19 of the lower crossbar 11 of the frame 9. The housing 1 is equipped with a strain gauge 20 for relative movement of the frame 9 for measuring the sediment of the medium sample 5 under the upper die 6 and the strainmeter 21 to control the compression ratio of the spring 16 and the corresponding pressure in the medium sample 5. The crossbar 10 is equipped with a hook 22, and the housing 1 from the side of the upper die 6 is screwed completely against the thread with a sleeve 23 rigidly connected to the guide sleeve 24 of the stop 7 of the upper die 6 and made with a latch for moving the upper die 6 in the form of a threaded locking screw 25 on the sleeve 24.

, Before testing the sample 5 medium for compression, the load device 8 of the compressometer is calibrated to obtain the dependence of the pressure p _i under the upper perforated stamp 6 on the amount of preload l _{i of the} spring 16 (Fig. 2): $$p_i=\frac{P}{F}=K\cdot l_i$$

,

where P is the compression force of the spring 16, F is the area of the upper stamp 6, K is the stiffness coefficient of the compression spring 16.

The compressiometer works as follows.

In the immediate vicinity of the sampling point, a cylindrical sample 5 of the medium is placed in the working ring 4 and with it in the working chamber 2 on the lower stamp 3. On the sample 5 of the medium, the stamp 6 is applied from above and the displacement stop of the stop 7 of the stamp 6 is mounted in the form of a threaded locking screw 25 on the sleeve 24 of the threaded cup 23 screwed onto the thread of the housing 1 of the device (Fig. 1). Set the load device 8 and the strain gauges 20 and 21. Then, by rotating the screw stop 19, the spring 16 is pressed to the first predetermined value l ₁ corresponding to i = 1 of the initial pressure stage p ′ ₁ (Fig. 2) and recorded by the strain gauge 21, while simultaneously loading preloading the spring 15 through the frame 9 and the pusher 14 is transferred to the stamp 6, which deforms the medium sample 5 with the initial pressure p ′ ₁ to the value p ₁ of stress relaxation in the medium and until the settling of the medium under the upper stamp 6 stabilizes to the value h ₁ , which is registered they are steered by a deformometer 20 at the moment of deformation stabilization l ′ _{1 of the} spring 16 fixed by the deformometer 21. The stop screw 25 fixes the movement of the stop 7 with the stamp 6 and sets the next stage of the initial pressure p _{2 of the} stamp 6 on the medium by pressing spring 16 by the value of l ₂ , release fixing the abutment 7 and is deformed sample 5 medium 6 to the time stamp of the initial pressure drop p _'2 to a value p ₂ h ₂ stabilization precipitation medium which is recorded deformometer 20 under steady readings l ₂ deformometer 21. The test cycle was repeated for by leduyuschego increasing the pressure on the sample 5 by the medium or its unloading, the value of each initial pressure stage p _'1, and the corresponding value preloaded spring 16 is set on the basis of the calculated relationship:

, $$l_i=p_i\left[\frac{\mathrm{one}}{Z}+\frac{F}{E_i}\right]$$

,

where p _i is the expected stage of establishment under pressure stamp 6; Z is the stiffness of the spring 16; E _i - the standard value of the deformation modulus of the investigated soil; Ф = (1-ν ² ) b is a coefficient depending on the Poisson coefficient ν of the medium, the coefficient ω of the form and the stiffness of the die 6 with a diameter of b ₀ .

Based on the test results and the standard method, the initial e ₀ and current e _i soil porosity factors are determined:

, $$e_i=e_0+\frac{\Delta h}{h}\left(\mathrm{one}+e_0\right)$$

,

build graphs of compression curves of compaction and decompression (figure 2) and determine the required mechanical characteristics of the medium.

The compressiometer has a simple design, has passed successful experimental tests. The device has a wide range of applications when testing soils and other materials for compressibility. For example, you can test both soft and frozen soils, and only the elastic dynamometer element is replaced with an element with greater rigidity. The small dimensions of the device allow it to be placed in the freezers of conventional refrigerators when testing frozen and thawing samples of the medium. Compression tests of the medium can be performed at any position of the device, which allows them to be carried out during the transportation of samples of the medium.

Information sources

1. Tsitovich N.A. Mechanics of frozen soils. - M.: Higher School, 1973. - S. 128-130. (analogue).

2. GOST 20276-99. Soils. Field methods for determining strength and deformability. - M .: MITKS, Gosstroy of Russia, 1999 (prototype).

3. Meschyan S.R. Mechanical properties of soils and laboratory methods from the definition. - M .: Nedra, 1974 - S. 20-22.

Claims (2)

1. The method of compressibility testing of a porous material medium, namely, that the prepared surface of the material medium is loaded with a rigid flat perforated stamp in a stepwise increasing static load stabilized in time t until the medium has lost the bearing capacity and stability of the stamp, the pressure parameters p are controlled in time _i and the corresponding deformations S _{i of the} medium at each increasing stage of loading, build a schedule for testing the medium in its conditionally stabilized at each loading conditions of states p _i = f (S _i ), according to the graph, the parameters of medium strength and deformability are determined, characterized in that at the initial and each subsequent increasing stage of medium loading with a stamp, a stepwise increasing medium deformation is set through an elastic dynamometric element, each increasing stage of deformation the medium is kept constant in time until its stabilization conditional upon relaxation therein stresses and stabilize the pressure p _i under the die, while subsequent steps before setting deformation and an elastic medium load cell fixed by a locking screw deformation load device. 2. A device for compressibility testing of a porous material medium, consisting of a housing with a working chamber, fixedly mounted on the bottom of the chamber of the lower rigid flat perforated stamp, a working ring with a sample of the material medium installed in the upper part of the working ring on a medium sample of the upper rigid flat movable perforated stamp, loading device, characterized in that the loading device consists of a rigid frame with upper and lower rungs and two guide racks, moving but installed in the vertical guide bushings of the housing, the pusher, rigidly connected with the upper crossbeam of the frame and resting through the ball against the stop of the upper stamp, an elastic dynamometer installed between the housing and the lower crossbeam of the frame and resting through the glass and the thrust bearing in the screw stop of the lower crossbar of the frame, moreover, the movable stamp is made with a lock of its movements and compression of the material medium, the stamp lock is made in the form of a locking screw for moving the pusher of the movable stamp.

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