A brief review of existing methods of calculating the coefficient of filtration (k). Of the existing and currently recognized methods of determining k by infiltration from pits, the method of A. K. Boldyrev is the most widely used, but obviously inaccurate, and only the methods of N. S. Nesterov and N. Y. Denisov combine the simplicity of calculation and sufficient accuracy. Their methods, in fact, only take into account, but do not take into account the complexity of the infiltration process. The whole process is as if excluded from the experience by the very construction of the method. In other words, the experience is made in a form that allows the calculations to consider only a part of the “water body” with the simplest water movement (N. S. Nesterov) or to solve a system of equations, in each of which the complexity of the movement is fixed by a simple coefficient (N. Y. Denisov). But these methods require either special equipment (N. S. Nesterov) or are too cumbersome to perform (by N. Y. Denisov). However, even N. S. Nesterov's method is not accurate enough, because in the central part of the “water body” he singled out, water particles move not only vertically, but also sideways.

Purpose and characteristics of the device. Self-recorder for groundwater level monitoring - limnigraph - is designed for automatic measurement and recording of water level changes in boreholes with diameter from 75 to 150 mm (Fig. 1 and 2). The limnigraph consists of (Fig. 3): body, winch, recording mechanism, steel rope, float, counterweight.

Electrolevel gauge is designed to measure the dynamic water level in wells during pumping (Fig. 1). The maximum depth measured by the device is 100 m, measurement accuracy + 0.05%. The operating principle of the device is based on the closing of the electric circuit between the tip lowered into the well and water, determined by the deviation of the galvanometer arrow (Fig. 2). The depth at which the circuit is closed is determined by the length of the insulated wire lowered into the well (see article). In conclusion, it should be noted that the above described electric level gauge gives quite sufficient accuracy for practice in measuring both static and dynamic water levels in wells at single and cluster pumping.

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.