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Change of depth of the diluted zone at concussion of water sated loess
DOI: http://dx.doi.org/10.20534/ESR-17-3.4-109-111
Rasulov Hayat Zoirovich, Tashkent Institute of Architecture and Construction, Doctor of Technical Sciences, Professor E-mail: [email protected] Tashhodjaev A. U., Tashkent Institute of Architecture and Construction,
senior teacher
Rasulov S. A.,
Tashkentlnstitute of Architecture and Construction,
magistr,
Change of depth of the diluted zone at concussion of water sated loess
Abstract: Article is devoted to questions of research on change of a diluted zone in the water sated loessial thicknesses in conditions of seismic fluctuations. To estimate a process depth of a diluted zone into thicknesses the formula serving a basefor the factor of dynamic consolidation of a soil at concussion is proposed. The given factor testifies the speed of consolidation of the particles broken by concussion in each special case is subject to experimental definition. The final size deep a diluted zone depends on time of influence of concussions.
Keywords: dilution; concussion; water sated thickness; loessial soils; factor of dynamic consolidation; seismic pressure; dynamic pressure; plastic cohesion, internal friction.
In building practice the cases of subsidence, an inclination, and, sometimes the destructions of buildings and constructions at strong Earthquakes are quite frequent. As one of principal causes of occurrence of such phenomena serves diluted and the subsequent non-uniform a settle water sated soils (loess) lying in their basis.
Despite actions undertaken against diluted soils the analysis of consequences of Earthquakes last for many years and shows all increase in deformations of the constructions erected on water sated soils.
This circumstance testifies that the problem diluted weak soils in the conditions of concussion nevertheless remains actual.
It is known, that under diluted we mean difficult process proceeding in dynamic conditions connected with infringement of structure of a soil, pressure occurrence in pore water and transition in a suspension of particles and soil transition in a fluid condition. The substantiation of such rather difficult process including simultaneously many physical phenomena, is one of a difficult problems of soil mechanics.
Results of researches are more rarely stated in works of authors concerning change of a diluted zone in thickness of a fluctuating soil in the course of fluctuations.
It is known that occurrence diluted in a certain part of soil thickness will happen in cases when seismic pressure within this thickness will exceed the strength indicators of soil [1, P. 66-68]. Within the given part, which have received the names «diluted thickness» forms seismic deformations (seismic subsidence) constructions in the conditions of Earthquake.
The spent experimental researches with water sated loess soils at various fluctuations have shown, that the border of originally formed diluted thickness is not constant size, and changes in the course of concussion. One of principal causes of such phenomenon is served by gradual reduction of force of plastic cohesion between fluctuating particles and simultaneous influence on them of the dynamic pressures arising at consolidation of broken particles of a soil.
Figure 1. Change plasticity cohesion in the course of fluctuation
In the course of concussion of the water sated soil the change of a condition of a soil is observed, for example, from plastic in a fluid condition. Development of such phenomenon will last to definite time after which expiration there will be already rather longer proceeding return process accompanied by consolidation of particles. During this
process the gradual restoration of the broken plastic connectivity of a soil is also observed. This circumstance is well seen from fig. 1., where dependence of kind L0=f (cw) for the investigated water sated loessial sandy loam is presentedOn the following drawing the reduction of quantity of connectivity of a soil makes in the beginning concussions
Section 9. Technical sciences
4,5 during 80 times in conditions of fluctuation of a soil with acceleration of2800 mm/s 2. The further concussion of a soil leads to attenuation of reduction of connectivity in considered conditions.
Based on results of the spent numerous researches it is possible to notice, that process of reduction of connectivity at concussion comes to the end on the average during 20-30 c. after the appendix of dynamic loading to a soil.
However, decrease in connectivity of a soil in the course of fluctuation in a number a case depends and on quantity of a dynamic pressure in water and filtration ability of a soil.
On fig. 2 the result of one of experiences of measurement of quantity of the dynamic pressures arising in a soil at its consolidation is illustrated. As noted in the schedule, the dynamic pressure
g 24
CO
«20 fa
116
arising in soil water increases with 0 to certain quantity in the course of concussion. Time of increase of a dynamic pressure, according to comparison of indications, is approximately equaled time of decrease in connectivity of a soil.
Thus, it is possible to note the below-mentioned simultaneous processes proceeding at concussion of water sated loess:
- gradual decrease in quantity of plastic cohesion within thickness of a soil;
- occurrence of dynamic pressures and its increase in time as a result of consolidation of the weakened communications of particles;
- decrease the general durability of a fluctuating soil.
<D &
O
1 g
5
s Sandv soil t
/ /
/
/ a=2200m m/s2
/ f z= =24« >m
10 20 30 40 50 60 70 80 90 100 120 140 The cours of fluctuation, s
Figure 2. Character of change
Reduction of durability of a soil as consequence of the above-named phenomena results entranced, in expansion of a diluted zone within thickness.
Studying thickness a diluted zone in the course of concussion makes a basis of the present research.
It is known, that the diluted zone always promotes reduction of durability and bearing ability of a soil. In cases, when durability of a soil decreases to a minimum (full diluted conditions) a loses soil a condition bearing ability and any loading on its surface will sink deep into thicknesses.
According to H. Z. Rasulov's theoretical work on"Conditions of dynamic durability water sated loessial soils" the diluted plastic-cohesion of the humidified loess is a consequence of reduction of resistibility to shift of soil s< w in result decrease cohesion (cw) and normal pressure from loading (J ) [2, P. 79-84]. Reduction of normal pressure occurs for the account weighing influence of a dynamic pressure hz, arising in considered conditions.
This circumstance is represented in a kind:
a) resistibility of the water sated loess in static conditions:
^ (P+Yw z)tgVw + cw (1)
b) same in dynamic conditions:
sdm= L(Pz +YwZ ) - YKZ ,t ] tgVw + Cw t (2)
For a case of absence of external loading on thickness of a soil:
Sdm= (YwZ K ,t )tgVw + cw t (3)
where: J - normal pressure from weight of external loading; Yw - soil density; Z - considered horizon in soil thickness; (pw - a corner of an internal friction of a soil; Cw - plastic cohesion between soil grains.
According to this formula we note the resistibility to shift of the water sated loess at concussion depends on quantity of change of cohesion of a soil and the dynamic pressure arising in a time of a soil at consolidation of particles which promotes decrease in influence of value of normal pressure. Thus the quantity of an operating dynamic pressure hz t in any depth z is defined under the formula:
of a dynamic pressure in time
h
L
z
(tor T ;
- *"At ),
(4)
where Vn - factor of the dynamic consolidation, testifying speed of consolidation of a soil; k, - factor of a filtration of a soil; H - a thickness of a fluctuating soil; z - depth of considered horizon; /U,A - the dynamic factors defined by practical consideration.
Let's analyse formulas (4). It shows that the dynamic pressure resulting in a diluted condition of thickness mainly depends on value of factor dynamic consolidation Vn. This circumstance testifies that the speed of a filtration of superseded water depends on the direct image of the speed of soil particles consolidation. this shows that the more the quantity of factor of dynamic consolidation, the more volume superseded from a time of a soil of water. It in turn raises degrees diluted thicknesses, simultaneously unloading underlaying layers of earth that promotes deep diluted zones in these conditions. On the basis told it is possible to notice, that expansion of a diluted zone in thicknesses also depends and on speed of consolidation of the destroyed particles of a soil.
The initial period of influence of concussions depending on dynamic durability of a soilin any part of thickness changes in a diluted condition (Lfl)The further process of fluctuations, on the basis of the above-stated, promotes deep this zone (Lt), that it is possible to track by carrying out of simple dynamic experiences on vibrating installations. Unlike sand, in loessial soils the given process is tightened in time, cohesion of a soil corresponding for infringement.
For the most simple case including this process linear, the differential equation of change of a diluted zone in time it is possible to present in a kind:
dLt = vL0 (t)dt (5)
where Vn - on former factor of dynamic consolidation, (1/c).
Integration of the equation (5) leads:
L = A + C e~
(6)
Constants of integration A andC are defined on conditions: t = 0 ^ L = L
V
Substantiating the parameters of operating elements of the enhanced chisel-cultivator
From here
t = œ -» L= H
A =H; C = H - L.
Taking into account (7) and (8) the formula (6) it will be copied in a following definitive kind:
Lt = H - (H - L) - e-' (9)
Formula (9) once again confirms the conclusion stated earlier about dependence deep diluted thickness in the course of concussion from speed of consolidation (vn ) a soil in these conditions.
(7) According to results of our researches it is possible to notice, that the quantity of factor of the dynamic consolidationtestifying
(8) the speed depends on many factors, most important of which are: conditions of initial density-humidity of a soil, value of plastic cohesion, coarse ground structure, and also intensity of concussion and character (on frequency and amplitude) this influence, etc.
At the same time for a substantiation of the difficult nature of factor vn special experimental researches and supervision are required.
References:
1. Ivanov P. L. Soils and the bases of hydraulic engineering constructions. - Moscow, - 1985. - 352 p.
2. Rasulov H. Z. Seismic stability of the soil bases, - Tashkent, - 1984. - 192 p.
DOI: http://dx.doi.org/10.20534/ESR-17-3.4-111-112
Tukhtakuziev Absusalim, chief of the laboratory, Research scientific institute of mechanization and electrification of agriculture, doctor of technical sciences, professor Toshpulatov Bekzod, competitor-scientific employee research, Research scientific institute of mechanization and electrification of agriculture, (Republic of Uzbekistan) E-mail: [email protected]
Substantiating the parameters of operating elements of the enhanced chisel-cultivator
Abstract: The research results substantiating the parameters of loosening and arrow-typed claws are specified in the article. It is enhanced in a purpose to reduce the power-capability and increasing the quality of soil crushing by the chisel-cultivator.
Keywords: chisel-cultivator, operating elements, loosening claw, arrow-typed claw, chess-typed arrangement, track by track positioning, blocked-type cutting, free cutting, angle of incoming the loosening and arrow-typed claws into the soil, solution angle and seizure width of arrow-typed claw, energy costs, quality of soil crushing.
In conditions of our Republic the chisel-cultivators are the main technical means at pre-sowing soil tillage proceedings. However chisel-cultivators (CHK-3,0, CHKU-4 and others) being applied currently have higher power-capability, and by single running it often doesn't ensure the required quality in soil crushing. Pursuant to above we have developed the enhanced chisel-cultivator. It consists of framework with hang-up, supporting wheels and operating elements installed in three row onto the framework.
Differing from the existing ones the operating elements of the first and second row of developed chisel-cultivator are installed on the frame as rows at staggered sequence, and the operating elements of the second and third rows -trace by trace; in this case the operating elements of the first and third rows are installed (regarding the supporting wheels) to the same stillage depth, i. e. their tabs are mounted in the same horizontal plane; the operating elements of the second row are installed on the less tillage depth (i. e. above) rather than the operating elements of the first and third rows.
In the process of running the enhanced chisel — cultivator the operating elements of the first row interact with soil monolith, i. e. they run in the conditions of blocked-type cutting, and the operating elements of the second and the third rows in the process of work interact with soil layers, zones bordering the loosened operating elements of the first row, i. e. run in conditions of free (deblocked-type) cutting.
The main task of operating elements of the first row is to form lateral loosened zones in order for operating elements of the second row to operate in condition of free-typed cutting. Therefore they are made in the form of dual-edged flat wedge, i. e. in a form of narrow loosening claw with a flat working surface. In this case, firstly the soil is deformed to the side of field surface, i. e. in the direction of open surface, secondly volume of being deformed soil is reduced in conditions of blocked-type cutting. As it is well known, [1] both of those two factors lead to reduce energy (power) expenditures for soil tillage.
Operating elements of the second and third rows of the developed chisel — cultivator is made in a form of a three-edged wedge, i. e. in a form of the arrow-type claw, and in this case efforts spent for soil deformation and destruction, they will direct to zones side loosened by the operating elements of the first row and the result is a reduction in energy costs [1; 2].
Arrangement the operating elements of the first and second rows at staggered sequence on the framework, and the second and third rows trace by trace, as well as the installation of the operating elements of the second and third rows stepwise (throughout soil tillage depth), i. e., the installation of the second row operating elements is higher than the third row relatively the operating elements of the third ensures layer by layer soil loosening; and consequently it leads to improvement of the its crushing quality.
