SU98789A1 - Apparatus for determining the amount of trapped air in granular soils - Google Patents

Description

When determining the permeability of sands and sandy loams in the aeration zone by the method of pouring into the hole, as well as in the study of filtration by monoliths, a very significant issue is. determining the amount of air trapped in the ground.

In the process of saturating the soil with water, especially if it is saturated from top to bottom, as is usually the case in natural conditions, tiny air bubbles remain in the pores of the soil, which, due to capillary forces, are trapped between the grains of the soil. These bubbles cannot be attracted by the movement of the filtering water and at the same time cannot rise up to the surface of the fruit. In this way, water filtration IS going on not by the total cross section of pores, but only by that part of them that is not occupied by air bubbles.

This circumstance makes it extremely difficult to compare the results obtained from pilot pumpings with data on fillings in pits and monoliths. This is explained by the fact that in the first case, a naturally saturated soil devoid of trapped air is subjected to testing, and in the second case, it is artificially saturated with water, and during the filling process itself, the soil under study contains more or less trapped air.

The proposed instrument is designed to experimentally determine the amount of trapped air in a sample of the soil being studied during infiltration. It is made of the type of instruments widely used for various soil tests, consisting of two communicating vessels, in one of which a sample of the test soil is poured with water, and the other is used for measurement.

A feature of the proposed device is the location of a vessel with soil inside a hermetically closed measuring vessel connected to a vacuum pump. A decrease in pressure in the measuring vessel causes the air trapped in the sample to expand and the water to displace. Increasing the water level in the measuring vessel allows you to determine the amount of trapped air.

FIG. 1 shows a vertical section of the proposed device; in fig. 2 - gas gauge installed in it (side view).

The device has a tube (1), which forms together with a perforated removable donyk

(2) with a lid (3) vessel for the sample of the soil to be tested. Top part of the cover

(3) made in the form of a transparent cylinder (4) with a hole closed by a rubber stopper (5). The outer measuring vessel is a glass (6) made of plexiglass and provided, at its primary, with a bottom (7) and an unscrewing cap (8). On the outer surface of the glass (G) there are divisions, as on a standard measuring vessel. The cap (8) is provided with a glass cap (9) in which a vacuum gauge (10) is placed, fitted to a form-shaped Tpy5i; ji. The shoulders of the U-tube differ in cross section. The part having a smaller cross-section, in the upper part, provided with a bubble, a friend and a half of the pipe from 1: a hole. Vacuumsgletr (10) zaolioliya non-divergent; children, such as oil or glycerium, so that the volume of air in the bubble and in a small part of T1; kill: and b1,1l is known and equal to, 1 cm, 1 cm under normal conditions, i.e. at a temperature of 20 ° and 760 mm of pressure. Under the nascaped conditions, the level of the liquid in the tube of the vacuum gauge (10) must match the scale of the free flow scale. 1. When pressure is measured in the measuring vessel (in glass 6), the air in the vacuum gauge (10) is expanded by pressing out the liquid. When access; 1; ke; n: and liquid U1) ram, marked on the scale is figure 2, the vacuum in the device will be the composition. (0.3 from atmospheric;: etc.) 7ak; ; with a titzer (11) for connecting a manual vacuum pump to an air tap (12).

Open vacuum gauge VL ;; et; | but prEpdinkalnaya detail) 10 51; ibora and can be replaced by a standard pointer vacuum wind.

To determine the number of lanes; c5; len air, the soil or monolith under test is placed into the tube (1) of the inner vessel, KOTOpHii can be selected by not pressing this tube into the hole of the hole or into the hole; A grid (13) is placed on the soil surface and the tube (1) with the soil is closed with a cover (3).

After that the rubber stopper (o) is removed, the cylinder is filled with distillate or well closed again with the stopper. The water oats gives ground and begins to filter through it from top to bottom, flowing out through a perforated bottom (2). When the water level in the cylinder (4) is lowered by the HHSIC holes in it, the rubber stopper (5) is removed and it, together with the tube (1) and the soil, is discharged into the glass (6) pre-filled with water so that after immersion in this water tsllin.shika (4) the water level is raised to the top. After this, the cylinder (4) is closed again.

using a stopper (5) and using a rubber band or nipetkn, the water level in the glass (6) is determined by the risk with the number O, which corresponds to 1; it starts with the limit of the scale. Then, the stacked screw (G) is tightly screwed on K1) the arm (8), the tap (12) on it is closed, and to the fitting (I) is replaced by a vacuum pump using a rubber tube, by means of which the air is drawn from the device to Achievement of a predetermined vacuum marked on the scale of the vacuum gauge.

Due to the decrease in pressure, i.e. the node under the action of vacuum, the air trapped in the pores of the sample begins to expand, and water is expelled from the soil. When this level of water in the glass (G) begins to rise. The installed vacuum of the nodder lasts for some time sufficient to stabilize the level of water in the glass, and then a reading of the rise in the level of water in the glass, i.e., the reading of water growth in it, is taken. The amount of trapped airflow, expressed as a percentage of the group volume, is determined by the formula:

WOV,

1/2 (“- 1)

where: Vi - oyem

Waters, prioavivsheys in dlngglye;

1 / 2-- o5b {:, 1 g) unta in the tube; and n is the multiplicity of vacuum and otpoygeiiiyu to atm. 1 spherioma pressure.

The proposed instrument provides the possibility of studying samples of monoliths and samples of d) whites with a non-random structure in both salt and laboratory conditions.

P re d m e and z o b r a f t

Prib (p for determining the amount of zantemolpny air, g, zerkppty soils of lrp infiltration, consists of two communicating vessels, one of which is filled with a sample of the test group filled with water, and the other is dead, HI, and ii with the fact that the vessel with the test gruit is located inside the hermetically sealed pressure gauge of the pressure gauge of the vacuum pump of the measuring vessel so that, due to the level of water in the iodine during iopin pressure, the content of the trapped air in pore ground.

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fC.

FIG. 2