1641
Technical Committee 203 /
Comité technique 203
Figure 6. Results of test of the condensed pillows
at explosive influence
14 THE BASES CONDENSED BY VERTICAL SANDY
DRAINS
In the Republic of Tajikistan territories mastered under
construction often can be put by big thickness (more than 15 m)
weak water-saturated loess soil of a soft plastic and fluid
consistence (I
L
≥ 0,8…1,0). In these conditions, and sometimes
and the unique method, before construction consolidation of
thickness by sandy drains is effective. For identification of
opportunity and efficiency of application of this method in soil
conditions of the republic natural pilot researches were
conducted.
The purpose of researches was studying of features of
consolidation of weak water-saturated loess soil at the device of
vertical sandy drains with the subsequent their loadings the
weight of a soil embankment in the conditions of static and
seismic influences. Researches were conducted on a platform
which on depth more than 16 m was put by water-saturated
lessial loams with consistence I
L
= 0,80, the calculation
resistance of R ≤ 90 kPa and the module of deformation E = 2,0
… 2,7 MPa. On an experimental areas 3 sites by the sizes of 10
x 10 m everyone were prepared. The first site was loaded
without the device of vertical sandy drains, on the second site
sandy drains on a grid 2 x 2 m, and on the third – on a grid 3 x 3
m, 6,0 m long and with a diameter of 0,4 m were arranged
(Usmanov R.A. 2009).. Transfer of static loading was carried
out by layer-by-layer dumping of an embankment from a gravel
and loamy material.
Figure 7. Scheme and results of consolidation of
soil by sandy drains
1- surface level markers; 2- deep level markers
It was thus established that the main part of deformations of
thickness of soil occurs during the first 5…6 days after the
appendix of each step of loading (fig. 5). By results of
supervision over development of layer-by-layer movements
more than 70% of the general deformations of thickness of
weak soil occurred at a depth of 3,0 m, and at a depth of 1,5 m -
more than 50%. After completion of works on consolidation of
deformation properties were conducted. Results of researches
showed that despite rather small size of condensing static
loading, value of calculation resistance of soil raised to R =
200…250 kPa (by 2,2…2,8 times), the deformation module to
2,4 times, the intercept cohesion in 1,6…2,0 times.
1
2
soil by static loadings, complex researches of their strength and
Figure 8. Scheme of vertical sandy drain
3
Imitation of seismic influence by intensity of 8-9 points on
the
3
4
a
1- embankment; 2- sandy pillow;
- vertical sandy drain; 4- weak soil
condensed massif was carried out by means of short delay
camouflage explosions of charges of explosive by a technique
given in fig. 2 and 3. By results of the made experiments (fig.
5) of an increment of additional deformations of condensed
thickness at explosive influences made about 30% from the
general a precipitation recorded at static tests that is obviously
connected with sharp increase of excessive hydrodynamic
pressure in steam water which promotes acceleration and
additional its filtration in sandy drains (Usmanov R.A. 2009)..
Figure 9. Development of deformations
THE STUFFED PILES
Operating experience of buildings and the constructions
ere
experimental sites in time
5
cted on the pile bases in various seismic regions shows on
reliability of their work in the conditions of weak water-
saturated soil. Taking into account it on weak water-saturated
loess soil of the republic researches on technology of the device
and features of work of ferroconcrete vibro-stuffed trailing piles
by diameter of d = 0,4…0,6 m and long L = 6,0…8,0 m were
