3139
Technical Committee 301 /
Comité technique 301
conditions of the republic application of the slabby and pile
bases which well proved in practice of high-rise construction of
many countries is also expedient.
1.2 Construction on weak water-satureted soils
In the Republic of Tajikistan, as a result of influence of a
number of natural and technogenic factors sharp lifting of level
of underground waters and flooding of the extensive territories
put by big thicknesses of earlier low-damp loess soil owing to
what they pass to category weak and strong compressibly (R ≤
100 kPа, E ≤ 5 MPa) is observed. Thus processes of flooding of
territories promote increase of seismic intensity of sites of
construction on 1…2 points. Now about 40% of the mastered
areas in the republic are presented by the specified soil and the
steady tendency of their increase is observed.
Effective design, construction and operation of buildings on
the specified soil are connected with application of various
methods of the device of the artificial bases and the foundations
taking into account high seismic activity of mastered sites. In
this direction the corresponding researches were conducted and
the following methods of the device of the bases and the
foundations (fig. 3) are offered for practical application
(Usmanov R. A. 2009):
a) The device high-condensed (
ρ
d
≥ 2,2 t/m
3
) sandy, gravel
and pebble pillows. Advantages – use of the simple equipment
and simplicity of the device; low cost and small labor input;
high reliability; existence of large volume of a local material.
Shortcomings – difficulties at the device during the winter
period; scope restriction with buildings to 6 floors.
b) The device of the bases from the driving and stuffed piles
which are cutting through a weak layer of earth. Advantages –
use of the modern equipment, reliability. Shortcomings –
substantial increase of cost and restriction of a scope of driving
piles at increase in thickness of weak soil; difficulties of quality
control of production of a stuffed pile and increase of its cost at
increase in length.
c) Fixing of soil by limy piles. Advantages – simplicity of
technology of the device and low cost of a method, refusal of
metal and cement application. Shortcomings – use of the special
equipment, complexity of quality control of works.
d) Consolidation of soil by vertical sandy piles. Advantages
– simplicity of technology of the device and low cost; existence
of sufficient volume of a sandy material; refusal of metal and
cement application. Shortcomings – use of the special
equipment; difficulties of quality control of works; considerable
labor inputs at the device and removal of a loading
embankment.
e) Consolidation of soil by vertical sandy drains. Advantages
– simplicity of technology of the device and low cost; existence
of sufficient volume of a sandy material. Shortcomings – use of
the special equipment; difficulties of quality control of works;
considerable labor inputs at the device and removal of
embankment.
Figure 3. Methods of preparation of the bases and the device of
the foundations on weak water-saturated loess soils
1- weak soil; 2- strong layer; 3- soil condensed pillow;
4- driving and stuffed piles; 5- limy piles;
6- sandy piles; 7- vertical sandy drains
All above-stated methods were investigated on joint action
of static and seismic (seismoexplosive) influences by intensity
of 8-9 points. Except the device of the high-condensed soil
pillows, other methods of preparation of the bases and the
device of the foundations can be recommended for the device of
the bases and the foundations of high-rise buildings. And
Figure 2. Methods of the device of the bases and the foundations on loess collapsing soil II of type:
1- loess collapsing soil; 2- non collapsing soil; 3- condensed soil pillow; 4- condensed thickness of soil; 5- drainage wells; 6- charges of
explosive; 7- soil piles; 8- bored piles; 9- lowering driving piles; 10- cement and sand filler
