RU2578514C1 - Groundwater viscosity meter - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention is designed to measure the viscosity of various cohesive soils and can be used in conducting engineering surveys for construction of buildings and structures. Clay viscometer is a triaxial camera type "B", wherein the lateral stresses transmitted to the cylindrical soil sample through a rubber membrane. Ends of the chambers are closed rigid fixed flanges. Vertical force is applied to a vertical metal rod passing through the central axis of the oven and the sample. Rod has a free lift in a vertical direction and is fixed to the loading device loading frame.

EFFECT: technical result is to adapt the design of the viscometer to determine the viscosity of the soil, reducing the complexity of research and extension of the scope to study the rheological properties of soils connected and disconnected.

1 cl, 3 dwg

Description

The invention relates to the field of measuring equipment, is intended for measuring the viscosity of various dispersed soils and can be used in engineering surveys for the construction of buildings and structures.

Currently, to determine the viscosity of soils, the most widely used standard device is a single-plane cut. However, this device, widely used to determine the strength parameters of soils, is unsuitable for the study of deformation and rheological processes. In these devices, the shear zone of the sample is small and uncertain, which does not allow one to determine with sufficient accuracy the relative shear strain γ. Among the disadvantages of a single-plane cut device is the variability of the working area of the sample, the limited deformation, the inconsistency of the gap between the upper and lower carriages, and the deviation of the cut surface from the plane. The use of warping devices (multi-plane cut) solves some of these drawbacks, but the magnitude of the deformations in them is also limited.

In addition to planar shear devices, a torsion test device was widely used to determine viscosity, which ensured that the test was carried out under pure shear conditions and allows the creation of practically unlimited deformations without changing the working area of the sample. However, this device is not without drawbacks, since it is difficult to create a complex stress state for torsion testing, in which, as a rule, soils are in real conditions. In addition, this device is technically complex and poorly reproducible industrially.

The closest analogue of the proposed device is a viscometer containing a continuous ball, which is placed in a medium on the bottom of the vessel, connected by a flexible thread thrown through the block, with a counterweight, the mass of which is greater than the mass of the ball. As a result of this, a rectilinear rectilinear motion occurs up to the surface of the measured body, while measuring the time the ball moves inside the body within a given path (ie, the speed of the ball) [SU 318854, G01N 11/10, 1971].

The disadvantages of this viscometer are:

1. Low accuracy in measuring viscosity, since during the movement of the ball inside the body under investigation, its speed varies from zero to maximum, i.e. significantly different from the assumed constant.

2. The high complexity of the measurement process due to the need for manual accurate measurement of the time of movement of the ball.

3. Limited scope due to the inability to use to determine the viscosity of dispersed solids, which include soils.

The aim of the invention is to adapt the design of the viscometer to determine the viscosity of the soil, reducing the complexity of research and expanding the scope for studying the rheological characteristics of cohesive and disconnected soils.

The viscometer (Fig. 1) is a type “B” stabilometer chamber (1) mounted on the base (2). A soil sample (3) is placed inside the chamber in a rubber shell. The space inside the chamber around the soil sample in the rubber shell is filled with distilled water, glycerin or air (4) - a medium to create pressure on the side surface of the sample. A metal core of constant cross section (5) passes through the central axis of the sample and is rigidly connected to the loading device. The UL60-4 unit manufactured by APS Antriebs- Pruf- und Steuertechnik GmbH (Germany) was used for this device, however, another with the same characteristics can be used.

A section along the longitudinal axis of the viscometer chamber is shown in FIG. 2. In FIG. 3 shows a diagram of the stress state of a soil sample in a viscometer chamber.

The viscometer operates as follows.

We set the task to determine the viscosity of the soil sample, if the speed of vertical movement of the rod is known. We assume that the resistance of the lower end of the rod is zero. We also assume that the shear mechanism of deformation of the soil surrounding the rod predominates. In this case, the rate of shear deformation of the soil around the rod will be determined based on the dependence

- скорость движения стержня, в м/с;Where

- rod speed, in m / s;

r is the radius from the center of the rod, in m, and

where τ is the shear stress, in kPa;

η is the viscosity coefficient, in kPa · s.

Expression (2) is valid at the moment when the resistance of the rod along the lateral surface is exhausted and the rod begins to sink into the ground at a constant speed.

The value of the vertical force transmitted to the rod depends on the value of the tangential stresses along the lateral surface of the rod, which can be determined based on the condition

where r _c and l _cm is the radius and length of the rod, in m;

) на стержень, в кН.F is the vertical force transmitted in the kinematic mode (

) on the rod, in kN.

Having made the assumption that the core material is not compressed, it is possible to determine the value of precipitation.

We use the substitution of condition (2) in (3) and then, after substituting the resulting expression in (1), we obtain

Integrating expression (4), we obtain

and taking into account the boundary conditions:

тогда

at

then

at

Expression (6) allows you to get the value of the speed of movement of the rod, taking into account the applied vertical load F and depends on the dimensions of the rod and the soil sample.

By transforming expression (6), we can obtain the value of viscosity at a constant speed of vertical movement of the rod

which allows prediction of the viscosity coefficient at various values of the speed of movement of the rod.

Thus, the installation for determining the viscosity of dispersed soils achieves a positive technical effect:

1. The design of the developed device is adapted for testing soils and soil materials. The developed viscometer makes it possible to determine the viscosity of cohesive and incoherent soils both in dry and in a water-saturated state, since the chamber of the device is sealed and preserves the given density and humidity of the samples.

2. The results of determining the viscosity in the developed device allow predicting the value of the viscosity of the soil at any value of the penetration rate of the rod, which is important for engineering surveys for geotechnical construction.

3. The design of the device is adapted for industrial production, as it is based on the industrial design of the chamber of a triaxial device of type “B” GT 2.3.6 produced by LLC NPP Teotek. Other structural elements are made by turning blanks of sufficient rigidity.

Claims (1)

A soil viscometer containing a cylindrical chamber with a sample of the soil under investigation in the shell, a load frame for creating axial force and a recording device for measuring displacements, characterized in that a constant-section rod is inserted into the sample, rigidly fixed to the load device and passing through the upper and lower sealed flanges cameras.

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