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Khojmetov Gaibnazar Khodievich, doctor■, of Technical sciences, professor, Tashkent Institute of Design Construction and Maintenance of Automobile Roads Kayumov Abdubaki Djalilovich, doctor, of Technical Sciences, Professor, Tashkent state Technical University Komilov Samandar Iskandarovich, Scientific researcher, Tashkent Institute of Design Construction and Maintenance of Automobile Roads E-mail: skomilov1974@mail.ru
DEVICES AND METHODS FOR DETERMINING THE PARAMETERS OF GEOSYNTHETIC MATERIALS - SOIL INTERACTION
Abstract: Devices and methods for determining the strength characteristics of geosynthetic materials - soil interaction are presented in the paper. The input factors and their limits, the planning matrix to process experiment results are also shown.
Keywords: automobile road, geosynthetic materials, stability, slope, angle of internal friction, traction, interaction, loading.
To confirm theoretical assumptions on the mechanism of interaction of reinforced elements (armoelements) with backfill soil, a complex of experimental studies has been carried out on a specially designed device on "pull-out" scheme, which most effectively reflects the processes occurring at "armoband-soil" contact and is close to the natural conditions of reinforced soil structure operation [1]. The design was developed taking into account the possibility to eliminate the shortcomings in existing test methods [2, 3], the main shortcoming being the presence of a fixed face side that does not allow reflecting (with sufficient reliability) the actual mechanism of interaction between the reinforced elements and soil. Experimental research is devoted to the determination of coefficients y and c when reinforcing soil with geosynthetic material. To carry out the experiments, a special device is created, the basis of which is the N. M. Maslov-Lurie device for the determination of soil coefficients $ and c with corresponding changes in the device.
The device to determine the strength properties of soil interacting with geosynthetic material (Fig. 1) consists of an upper loading stamp 1, an upper 2 and a fixed lower 3 rigid rectangular holders, 10 x 20 cm in size, the base 5 rigidly attached to the main body ofthe Maslov-Lurie device; a sample of geosynthetic material (GM) 6 is fixed in a special frame 8 by half the length of the holder with screws 9, the reduction in frictional forces in motion is achieved with the balls 11 located in the grooves 13. Components of the device are shown in (Fig. 1).
On the surface of soil, a stamp 1 is set and a vertical load Q is applied, simulating the weight of soil (road pavement) with 1 hour exposure before the beginning of experiment.At each value of vertical loads Q (not less than three), taken in such a way that the range of their changes encompasses the actual steps in the road structure (at least 6-8 during the test period), a horizontal load Pz is applied with fixation of GM displacements at the points II-IY by the indicator of watch type. To measure the displacements along the width of geosynthetic material at points II-IY, metal tubes 14 with inner diameter of 1 mm are laid in the ground, inside the tubes a thin string 15 is inserted, one end of which is fixed to geosynthetic material, the other end to the indicator 16.
In calculations, the average value of indicators at points II-IY is taken, which increases the accuracy of the experiment. The exposure time at each stage of horizontal load is selected from the test before steady displacement occurs at points II-IY, and the exposure time at each loading stage should be sufficient only to detect the stabilization of displacement.The experiment is considered complete, if the displacement at point I of the frame with geotextile material. The value of horizontal load Pr, corresponding to the end of experiment, is taken as the limiting value. The processing is carried out by plotting the function y = f(Q), where y = Pr /2F (F is the area of the part of the sample fixed in soil) and by determining the values of strength characteristics y and c similar to the definition of y and c in the plot of soil shear.
DEVICES AND METHODS FOR DETERMINING THE PARAMETERS OF GEOSYNTHETIC MATERIALS - SOIL INTERACTION
a)
b)
c) d)
Figure 1. List of parts of the device to determine strength indicators: a - upper holder; b - frame for GM; c - lower holder; d - loading stamp
Figur 2. Sectional drawing of test scheme to determine the parameter of soil - geomaterial interaction; 1 - stamp; 2 - upper holder; 3 - lower holder; 4 - screw; 5 - adaptation to connect to the base; 6 - sample of geosynthetic material; 7 - left fixing attachment; 8 - frame; 9 - attachment screw; 10 - right fixing attachment; 11 - balls; 12 - frame screws; 13 - groove; 14 - metal tubes; 15 - metal wire; 16 - indicator of watch type
After formulating the goals of research and choosing the factors, establishing the repeatability [4] of the experiment, we proceed to experimental plan. The choice of the scheme for conducting the experiment is determined depending on the purpose of the study - construction of a mathematical model, number of influencing factors, necessary accuracy in
determining the coefficients. In experiments it is planned to investigate the effect of three factors on slope stability:
moisture content of soil ( W), coefficient of compaction (Ky), soil type (Ip). It is assumed that W varies from 13% to 21%, Ky - from 0.96 to 1.0, Ip - from 1 to 7. Experimental plan is presented in (Table 1).
Tablel. - Values of factors
№ experiment Moisture content W Coefficient of compaction Ky Soil type Ip
1 21 1 7
2 13 1 7
3 21 0.96 7
4 13 0.96 7
5 21 1 1
6 13 1 1
7 21 0.96 1
8 13 0.96 1
O facilitate subsequent calculations, from natural scale of independent variables we would transfer to some standard
Table 2. - Factors limits
(code) scale, denoting W by X1, Ky -X2, I-X3.Proceeding from the above, table (Table 2.)
Factor Lower limit Middle limit Upper limit Intervals
W 13 17 21 4
K 0.96 0.98 1 0.2
I -p- 1 4 7 3
Is built showing the change in the limits of factors and the range of limits variation. So, Table 1 can be written in the form of (Table 3).
Table 3. - Matrix of experiment
№ experiment X. X2 X3
1 + + +
2 - + +
3 + - +
4 - - +
5 + + -
6 - + -
7 + - -
8 - - -
Results of this experimental plan allow us to estimate the The goal is achieved by determining the coefficients of the
coefficients of linear equation of regression. equation of regression. Values of coefficients are determined,
y = a 0 + alxl + a2x 2 + a3x 3 + a1 2x1x 2 + from these values the regression equation is derived to define
+a x x + a x x + a x x x strength characteristics of geosynthetic material.
1 3 1 3 2 3 2 3 1 2 3 1 2 3
References:
1. Proc. of the International Scientific -Technical Conference "Prospects of Road Transport and Engineering Communication Infrastructure" part-1.- Tashkent - 2017.- P. 73-76.
2. Soil-Geosynthetics Interaction: Modeling and Analysis Mercer Lekture,- 2007-2008. Ennio M. Palmeira. University of Brasilia, DF,- P. 70910-900.
3. The 12th International Conference of International Association for Computer Methods and Advances in Geomechanics (IACMAG) 1-6 October,- 2008. Goa, India Experimental Investigation and Numerical Analysis of Reinforced Geologic Media.Hema Siriwardane, Raj Gondle, Bora Kutuk and Ronald Ingram. Department of Civil and Environmental Engineering, West Virginia University, Morgantovn, WV USA.
4. Adler Yu.P., Markova E. V., Granovsky Yu. V. Planning of Experiments in Search for Optimal Conditions.- Moscow: Nauka,-1976.- P. 141-154.
