Study of Vibratory Compaction of Fine-Grained Materials at Different Moisture Contents
Abstract Generated abstract
This study examines how moisture content and granulometric composition affect the vibratory compaction of fine-grained materials. Laboratory experiments were conducted on Tashlinsk quartz sand and marshalite using an electrovibrational stand at 100 Hz and 0.45 mm amplitude, with bulk density measured before and after one minute of vibration. The results indicate that vibratory compaction generally increases with moisture content, weakly for the coarser, more homogeneous quartz sand and more strongly for fine-grained marshalite. Compactability decreases up to the maximum molecular moisture capacity and then rises at higher moisture contents, with the breadth and clarity of the low-compactability interval depending on particle-size composition.
Full Text
STUDY OF VIBRATORY COMPACTION OF FINE-GRAINED MATERIALS AT VARIOUS MOISTURE CONTENTS
V. A. Trofimov, V. M. Vityugin
(Presented by the scientific seminar of the Department of General Chemical Technology)
Recently, vibratory treatment of materials has been increasingly used in various branches of industry. The method of low-frequency vibratory treatment of materials is highly effective, making it possible to obtain the maximum packing density, close to the theoretical value calculated from the granulometric composition of the materials. Questions of soil compaction at different moisture contents were examined in detail by A. F. Lebedev [1], but in that work the nature of the compaction of materials is closer to pressing processes than to the processes that occur during vibratory compaction.
The purpose of the present investigations was to determine the dependence of vibratory compaction on the type of material and its granulometric composition at different moisture contents. Tashlinsk quartz sand and marshalite from the Bolotovo deposit were taken for the study. The granulometric composition of the materials is presented in Table 1.
Table 1
| Particle diameter, mm | Amount, % | Amount, % |
|---|---|---|
| Tashlinsk sand | Marshalite | |
| 0.5–0.20 | 93.30 | 1.40 |
| 0.20–0.18 | 4.05 | 1.95 |
| 0.18–0.16 | 1.70 | 2.10 |
| 0.16–0.14 | 0.26 | 1.35 |
| 0.14–0.10 | 0.32 | 2.40 |
| 0.10–0.08 | 0.04 | 6.30 |
| 0.08–0.05 | — | 54.20 |
| —0.05 | — | 29.89 |
| Total | 99.67 | 99.59 |
| Losses | 0.33 | 0.41 |
| Total | 100.0 | 100.0 |
Vibratory compaction was carried out on a laboratory electrovibrational stand. The materials were compacted in a cylindrical beaker with an area of 6.41 cm², having a vertical graduation in mm. The frequency and amplitude of the vibrations were measured with a VR-1 vibrograph, and the operating time with a stopwatch. At this stage of the work, vibratory compaction was carried out at a frequency of 100 Hz and an amplitude of 0.45 mm for 1 min.
A weighed portion of preliminarily dried material was moistened, thoroughly mixed, sieved through a 3 mm sieve to obtain homogeneous aggregates, and the given amount of moistened material was freely poured into the beaker. After vibratory treatment, the height of the compacted material was measured and the bulk density was calculated. Changes in the bulk densities of the materials as a function of their moisture content without compaction and during vibratory compaction are presented in Fig. 1, and the dependence between the degree of compaction …
$K$ of materials at different moisture contents is presented in Fig. 2. The degree of compactability $K$ is expressed by the following formula:
\[ K=\frac{\gamma_1' - \gamma_1}{\gamma_{\mathrm{opt}} - \gamma_1}, \]
where $\gamma_1'$ is the unit weight of the material after vibratory compaction at the given moisture content,
$\gamma_1$ is the unit weight of the material without compaction at the given moisture content,
$\gamma_{\mathrm{opt}}$ is the maximum unit weight obtained after vibratory compaction of the given material at the optimum moisture content.
The physical meaning of the above value of the degree of compactability is that it characterizes the capacity for compaction by vibration of materials differing in their nature at different moisture contents.
Fig. 1. Dependence between the moisture content of materials and the change in their unit weight; 1 — quartz sand without compaction, 2 — marshalite without compaction, 1′ — quartz sand under vibratory compaction, 2′ — marshalite under vibratory compaction, 1″ — degree of compaction of quartz sand, 2″ — degree of compaction of marshalite (the ordinates of these curves are the difference between the ordinates of curves 1′, 2′ and 1, 2).
Fig. 2. Degree of compactability of materials at different moisture contents: 1 — quartz sand, 2 — marshalite.
Analysis of the curves presented in Figs. 1 and 2 shows that, with increasing moisture content of the materials, the degree of vibratory compaction (curves 1″ and 2″ in Fig. 1) increases, only slightly for the more coarse-grained homogeneous Tashli quartz sand and more intensively for marshalite. Vibratory compaction is most effective for materials at moisture contents above the value of their maximum molecular moisture capacity. As the moisture content increases up to the value of the maximum molecular moisture capacity, the degree of compactability of the materials decreases, and with a further increase in moisture content it increases (curves 1 and 2, Fig. 2). The width of the moisture-content interval of the material with the minimum degree of compactability depends on the granulometric composition. For the relatively coarse-grained quartz sand, the minimum compactability is clearly expressed, whereas for fine-grained marshalite the low degree of compactability is spread over a large moisture-content interval.
LITERATURE
- A. F. Lebedev. Compaction of soils at different moisture contents. Stroiizdat, 1949.