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Sayfiddinov Sadriddin associated-professor, Tashkent Institute of Architecture and Civil Engineering Tashkent, Republic of Uzbekistan Е-mail: [email protected]
DYNAMIC PROPERTIES OF ANTHROPOGENOUS SOILS
Abstract: The article deals with the dynamic research of anthropogenic grounds in the basement of buildings. Designing and erection of buildings structures on weak soils in seismic regions.
Keywords: Anthropogenic soil, stability, intensity, ball displacements, internal friction, hour-type indicator, duration of oscillation.
Introduction
Dynamic properties of anthropogenic soils lying on the territory of ancient cities of the Republic of Uzbekistan little studied. There are no recommendations for ensuring the stability of such soils under the influence of dynamic (seismic) loads on them.
In order to fill this gap, we carried out studies devoted to the study of factors affecting the process of weakening the strength of anthropogenic soils under conditions of oscillation. This
Table 1. - Characteristics
The vessel with the sample under study was equipped with appropriate measuring instruments. To measure the pressure that occurs when the soil oscillated in water, a pressure sensor with a record of the digital storage oscilloscope used. The TDS2000C series.
Sediment of the sample fixed by means of a dial indicator mounted on the end of the rod attached by the other end to a perforated plate placed on the surface of the sample. The test soil subjected to a vibration of 5-10 minutes.
The results of the experiments showed that the deformation of the soil in the process of oscillation, like loess soils, begins after a certain time (from several to tens of seconds) after application of a dynamic load on the soil, which turned out to be a distinctive feature ofcohesive soils from disconnected soils. A further rapidly increasing character of the deformation of the soil noted during its oscillation, which well seen in (Fig. 1).
At the same time, the readings of the pressure sensors are slightly different from the indications of the indicator. In
circumstance caused the necessity of conducting a complex of studies on a vibrating installation with observation ofthe deformation of anthropogenic grounds of different composition and state under the action of different dynamic loads. In these studies, simultaneously with deformation of the soil, observations were made of the immersion of a ball mounted on a soil sample.
The studies carried out on disturbed and undisturbed soil samples, the physical and mechanical characteristics given in (Table 1).
of the investigated soils
these experiments, the pressure in the water begins to grow from a certain moment after the application of a dynamic load on the soil, which is obviously a consequence of the disturbance of the soil structure under very difficult conditions (Fig. 2).
The absence of compaction of the soil until a certain time, as we discovered earlier in the study of loess water-saturated soils, indicated the processes occurring under these conditions, associated with a change in the internal bonds of the soil.
It could be assume that in many experiments, with the moment of the appearance of excess pressure in water, the strength of the soil appeared to drop, as evidenced by some experiments conducted with sample overload. These experiments carried out half-round in diameter, round loading on the surface of the ground, representing a metal ball 1.0-2.0 cm in diameter (the diameter of the ball chosen depending on the initial condition of the plasticity of the soil, which freely retained by the soil prior to vibration.
№ Soil Natural humidity % Density The porosity of the soil% Characteristic humidity Coal of internal friction General adhesion
Dry ground g/ sm3 Natural soil g/sm3
WL W R
1. Soil № 1 10 1.40 1.54 48.0 27.8 19.8 29.0 0.015
2. Soil № 2 14 1.44 1.61 46.0 27.5 20.1 29.2 0.025
3. Soil № 3 11 1.50 1.70 44.0 26.7 18.0 28.1 0.010
5. Soil № 5 16.5 1.43 1.67 47.0 26.5 20.1 27.0 0.005
6. Soil № 6 13 1.47 1.80 45.8 29.0 17.8 27.0 -
Section 2. Biology
Figure 1. Change in the porosity of anthropogenic soil, depending on the duration of the oscillation Ground number 5, acceleration of oscillation 1800 mm/s2
Figure 2. The nature of the change in dynamic pressure for anthropogenic soils. On the graph: the upper line corresponds to the ground No. 2, and the lower line to the ground No. 1. Acceleration of the oscillation 2500 mm /s2.
To measure the displacement of the ball along the ground, a steel rod with a diameter of 6 mm and a length of 30 cm welded on its surface, with the indicator leg at its upper end.
To maintain the vertical displacement of the ball along the ground, its rod passed through the guide hole of the special frame rigidly attached to the vibrating plate of the installation.
In these experiments, the ball immersed in the soil practically simultaneously with the increase in pressure in the water, which indicated the beginning of the disturbance of the soil structure and its transition to a dynamically disturbed state. Table 2 gives data on the results of one cycle from a series of experiments.
Table 2.- Change in pore pressure, ball deformation and sediment of the soil surface in time at a = 1500 mm/s2
№ Type of experimental measurement Eg. H3M Duration of oscil lation, sec.
5 10 15 20 25 30 40 50 70 90 100
1. Pore pressure mm - - - 2 5 8 10 12 16 20 20
2. Dipping ball mm - - - 2 3 5 7 8 12 14 14
3. Soil precipitation mm 3 4 6 8 10 10 10
Conclusions
Based on such studies it was possible to conclude that, unlike sandy soils that can compact immediately after mechanical destruction of the structure, anthropogenic soils, similar to loess soils, undergo complex internal transformations before the beginning of the compaction process, which are associated with a disruption of their connectivity under conditions of
continued oscillation. However, the rate of disturbance of the internal bonds of anthropogenic soils proceeds more slowly than in loess soils, as evidenced by experiments on measuring the immersion of a ball.
This seems to be explained by the fact that the structure and texture of anthropogenic soils is much more difficult compared to loess.
References:
1. Rasulov Kh. Z., Sayfiddinov S., Khakimov G. A., Chastoedov Y. N. Sedimentary deformations of loess soils under dynamic influences,- Materials of the 6th All-Union Congress on Theoretical and Applied Mechanics,- Tashkent,- 1986.- 5340 p.
2. Rasulov Kh. Z., Sayfiddinov S., Khakimov G. A., Chastoedov Y. N. Seismic data on loess soils. Proceedings of the All-Union Conference on the Dynamics of Foundations and Underground Structures.- M.: - 1989.- P. 179-180.
