On the Possibility of Using Glued Panel Floor Structures

A. P. Andrianov

(Presented by the scientific conference of the Mining Operations Faculty)

In the underground mining of coal deposits, a large quantity of mine timber is consumed. In some cases the consumption of timber reaches as much as 70 m³ and more per 1000 tons of coal. In this, high-quality industrial wood is often consumed. Therefore, the economical use of timber and the search for ways to put low-grade wood to use is an urgent task.

At present, a number of scientific research institutes are successfully solving the problem of finding ways to economize on forest materials. The work of TsNIIPS, of the All-Union Scientific Research Institute of Railway Construction and Design, of the Scientific Research Institute of the Ministry of Machine Building, as well as construction practice, have shown that the introduction of glued structures gives an economic effect and, moreover, makes it possible to obtain timber “rolled stock” of any cross section and length from ordinary small-sized material. In this, a considerable portion of the timber (up to 40%) used is of reduced quality. Tests carried out on glued piles and sheet piles after a year and a half under water revealed [1] that the principal distinguishing feature of glued structures is their monolithic character, ensured by the rigidity and non-yielding nature of the glue seams. In the nature of their performance they approach welded metal structures and are calculated as monolithic.

For gluing wood, casein-cement glue is used; it ensures high strength and fungus resistance of the glue seam and is comparatively cheap and simple in application. Tests of the strength of the glue seam on a casein-cement mortar for pine with a moisture content of 18% show that 100% of failures occur in the wood [2]. Experiments also confirm the possibility of gluing wood with a moisture content of up to 40% with casein-cement glue [1], which is of great practical importance.

Taking into account the practice of civil and industrial construction, as well as data from scientific research institutes on the use of glued wooden structures, it seems possible to us, instead of lagging, in the panel system of mining, to use decking made of glued boards for the panel floor.

In the mines of Kuzbass, much high-quality wood is often lost.

wood only because it does not correspond to the required dimensions. In a glued floor, this “non-grade” timber will be fully utilized, which will make it possible to save a large quantity of timber.

Construction of Glued Panels

Glued wooden panel floors may be used in three variants:

1) in the form of a continuous flat monolithic decking;
2) in the form of separate glued beams (timbers);
3) in the form of monolithic decking of trapezoidal shape in cross section.

A continuous flat decking may be made from boards glued together in the form of a continuous monolithic wooden slab, covering the metal base of the panel section, which will perform the function of a roll-out decking when the panels are fastened (Fig. 1). Such decking may be made of any dimensions.

Fig. 1. Continuous flat monolithic decking

A panel floor made from separate glued beams consists of boards glued together, laid in several rows one on top of another. The resulting glued beams, with a length equal to the dimension of the panel in height, are laid in a single row across the sheet span like an ordinary roll-out decking (Fig. 2).

Fig. 2. Glued beams for a panel floor

Monolithic decking of trapezoidal shape in cross section is also assembled by gluing together boards of different lengths (Fig. 3). To establish the most rational

Section across the sheet span    Section along the sheet span

Fig. 3. Monolithic decking of trapezoidal shape in cross section

forms of flooring, it is necessary to know the nature of the distribution of rock pressure on the panel floor structure.

Strength of a Glued Panel Floor Structure

Glued structures are calculated as monolithic ones [4]. In calculating strength, we consider glued panel floor structures as beams resting freely on two supports, with the load distributed according to a parabola. Table 1 gives the loads for different sizes of panel floor structures, determined by the formula of M. M. Protod’yakonov—

\[ P = \frac{4}{3}\,\delta \gamma \frac{a^2}{f}, \]

where \(\delta = 1.6\ \mathrm{t/m^3}\) is the unit weight of the rock in a loosened state; \(a\) is one-half of the design span of the panel floor structure by thickness, m; \(f = 0.6\) is the strength coefficient of the rock in a loosened state; \(\gamma = 1.5\) is the dynamic coefficient for a panel installation spacing of \(0.5\ m\).

Table 1

The heights of equally strong panel floor structures made of round timber and of flat glued flooring are given in Table 2. In determining the strength of the flat glued flooring, the coefficient of working conditions of the glued structure \(m_u = 0.8\) was taken into account [6].

Table 2

Consumption of Materials and Cost of Panel Floor Structures

The consumption and cost of timber materials for panels of ordinary and glued construction are given in Table 3.

Table 3

The consumption and cost of glue for the glued panel floor are given in Table 4.

Table 4

The cost of materials in Tables 3 and 4 has been taken according to the corresponding price lists. The cost of metal is not taken into account, since its consumption in both panel structures is the same.

The volume of work and wage costs for installing 4-section floors are given in Table 5.

Table 5

The norms and rates for installation of an ordinary panel have been adopted according to data from mines of the Kiselevskugol Trust (Kuzbass). There is no practice of gluing panel floors. Therefore the norm of 0.75 m³/man-shift has been adopted from experience in manufacturing models of such panels in the laboratory of the Department of Development of Bedded Deposits of the Tomsk Polytechnic Institute. The cost of one man-shift in both cases has been taken as the same.

The total cost of panel floors is given in Table 6.

Table 6

Conclusions

Preliminary calculations show the following.

1. The use of glued panel structures makes it possible to install monolithic panel floors of any dimensions. This makes it possible to cover a thick seam with continuous decking, eliminating the weak joints—splices—that occur when ordinary single panels are installed over seams more than 7–8 m thick.

2. The consumption of construction timber is significantly reduced (Table 3).

3. A strong glued panel floor of small height will eliminate labor-intensive and costly work on driving and maintaining high crosscuts in thick seams.

4. The labor input for preparatory and installation work is reduced (Table 5).

5. The cost of manufacturing the panel floor is reduced, and consequently the cost of coal extraction will decrease.

Literature

1. Kagan M., Yavlensky S., Sokolovsky B. Glued piles and sheet piling. Morskoi flot No. 7, 1951.

2. Central Scientific Research Institute of Industrial Structures (TsNIIPS), Problems of Strength and Manufacture of Wooden Structures, Moscow, 1952.

3. Chinakal N. A. System of Mining with a Panel Floor, Gostekhtopizdat, Moscow–Leningrad, 1943.

4. Karsen G. G., Bolshakov V. V., Kagan M. E., Sventsitsky G. V. Wooden Structures, Moscow, 1952.

5. Bykovsky V. N. Glued structures made of unplaned boards, Research: Wooden Structures, Moscow, 1953.

6. Standards and Technical Specifications for the Design of Wooden Structures, Gosstroiizdat, Moscow, 1955.