In laboratory practice up to the present time for determination of filtration coefficient of cohesive rocks two types of devices are used: N. V. Kolomensky and PV - Znamensky and Haustov's design. But these devices are designed either for small heads expressed in fractions of atmosphere (PV) or for cores of large diameter (N.V. Kolomensky device). The device described in this article is designed and actually applied by us for determination of filtration coefficient of cohesive rocks under pressure of 2-3 atm at core diameter of 35 mm. Some features of the E. E. Kerkis device, designed for determination of the filtration coefficient of loose soils, were partially used in the construction of the device. The device for pressure filtration (Fig. 1) consists of a cylinder 5, two flanges 1 with grids 2, clamping rings 3 and rubber gaskets 4. A core with a diameter of 35 mm and a height of 20 mm is loaded inside the cylinder. The gap between the conical part of the inner surface of the cylinder and the core is filled with resin. When selecting the resin, it should be borne in mind that excessive plasticity may cause the resin to float on the bottom surface of the core, which will reduce the filtering surface. Therefore, a harder resin should be used.

Central well. When organizing experimental pumping, the dynamic water levels in the central well are usually left out of observations, as the water-lifting pipe is filled with emulsion masking the position of the dynamic level. To observe dynamic levels, a special observation well of small diameter (piezometer) in the immediate vicinity of the central well is installed, and it is called a downhole observation well. At deep occurrence of the dynamic level in the aquifer, the sinking and anchoring of the downhole well becomes difficult. It is very convenient to replace such a well with a piezometric tube lowered into the central well next to the air pipe. If the lower edge of the piezometric tube is immersed 5-10 m below the mixer, the water in it is completely free from the impact of air supplied to the central well and set at a level corresponding to the dynamic level in the central well and aquifer. It remains only to periodically measure the position of this level with a level gauge. B.P. Ostroumov's level gauge is convenient.

The mixing of two waters with different concentrations and chemical compositions can be analyzed by the graph-analytical method proposed by A. N. Ogilvy. Having established the rectilinear law of mixing two waters, A. N. Ogilvy constructs a graph in a rectangular coordinate system, plotting the total mineralization of the mixed water along the x-axis, and the content of individual components in the mixing waters along the y-axis. Such a graph-nomogram does not make it possible to take into account the volumes of mixing waters. The nomogram we propose compensates for the shortcoming of A. N. Ogilvy's graph and can be used in cases where it is necessary to determine the quantities of mixing waters. The nomogram we constructed is based on the law of change of all components of mixing waters according to the equation of a straight line established by A. N. Ogilvy. The content of components in mg/l or g/l from 0 to any value limited by the data of chemical analysis is plotted along the y-axis in a certain scale. The divisions convenient for calculating the ratio of the volumes of mixing waters are plotted along the x-axis, let's put it from 0 to 10 or, more conveniently, from 0 to 100. The left column of the nomogram (y-axis) is allocated for the components of one of the mixing waters, the right one - for the components of the second water.