1523
Ensuring Stability of Boards of Deep Ditches in Seismic Regions
Assurer la stabilité des fossés profonds dans les régions sismiques
Khomyakov V.A.
Kazakh Leading Academy of Architecture and Civil Engineering, Almaty, Kazakhstan
ABSTRACT: Questions of ensuring stability of boards of ditches up to 24 meters in depth are considered at subway construction in
Almaty. Difficulties cause such factors as density of building of the territory, heterogeneity of an engineering-geological structure and
the increased seismicity of the territory. Results of laboratory and field researches on specification of strength and deformation
parameters of soil are given. For a case of a superficial driving of the subway it is set an example fixing of boards when developing a
ditch up to 25 meters in depth. For fixing of slopes the combined scheme in which excavation of a ditch is accepted both without
fastening, and with fastening of boards of a ditch in the form of retaining walls and vertical racks in the form of piles is accepted.
Stability of a protection is provided with inclined soil anchors. Bearing ability of anchors at static and seismic loadings was defined by
field tests and laboratory researches of models of a slope in a tray.
RÉSUMÉ : On examine les questions de la stabilité des bords des fouilles par la profondeur jusqu'à 25 mètres à la construction du
métropolitain à Almaty. La complexité de l'exécution de la construction est provoquée par tels facteurs comme la densité de la
construction du territoire, la non homogénéité de la structure géotechnique et une haute sismicité du territoire. On amène les résultats
des études de laboratoire et champêtres selon la précision прочностных et деформационных des paramètres du sol. Pour le cas du
fonçage superficiel du métro on montre l'exemple de la fixation des bords à l'élaboration de la fouille par la profondeur jusqu'à 25
mètres. Pour la fixation des pentes on accepte le schéma cumulé, dans qui l'élaboration de la fouille est acceptée sans fixation, ainsi
qu'avec la fixation des bords de la fouille en forme des murs de support et les comptoirs verticaux en forme des pilots. La stabilité de
la barrière est assurée par les ancres inclinés dans le sol. La capacité portant des ancres aux charges statiques et sismiques était définie
par les essais champêtres et les essais de laboratoire des modèles de la pente dans l'éventaire.
KEYWORDS: underground, seismicity, soil, durability, deformation, ditch, anchor.
1 INTRODUCTION
Modern construction of the densely populated cities
demands intensive development of underground space which is
necessary for development of engineering support, a solution of
the problem of autoparkings, underground public transport,
creation of the additional areas, etc. But the solution of these
questions is most complicated. Existing buildings, are expensive
and engineering communications interfere with a construction
of new underground constructions. The intensive development
of the city resulted Almaty (Kazakhstan) in need of
improvement of its infrastructure. About 10 large automobile
outcomes on internal and ring highways were constructed.
However it only partially solved transport problems.
Automobile jams remained a big problem. In 2011 in Almaty
the first line of the subway was started. The main part is located
at a depth of 60-35 meters. It is constructed in the underground
way and it is located only in the central part of the city. Again
under construction second line covers new areas. Density of
building of the territory here not so big. Therefore for economy
construction of a new branch is planned in the open way.
2 GEOLOGICALSTRUCTUREOFTHETERRITORY
The territory of construction is located on the inclined
foothill plain, a strip along a northern slope of ridge Zailiysky
Ala Tau. Within the line of the subway the accumulative type of
a relief is widespread. In the geomorphologic relation the site is
located within the foothill loop formed as a result of merge of
cones of carrying out of the mountain rivers. Surface flat, with a
bias from mountains to the plain. The surface is crossed by a
river valley Big Almatinka with depth of cutting of 5-6 m.
Boards cool, from a surface are put by loams, is deeper –
boulder and pebble soil with sandy, loamy and sandy filler.
Prolyuvialny deposits of verkhnechetvertichny age (apQ
III
) take
part in a geological litologichesky structure of a section
allyuvialno rom physic-geological processes there is an
insignificant plane washout, high seismicity [SNIP RK 2006].
On a site of a line of underground up to the investigated
depth of 24,0 m it is allocated 5 engineering - geological
elements. GL-1-a bulk ground - capacity of a layer of 0,2-2,7 m.
GL-2 - a soil - vegetative layer, loam with roots of plants.
Capacity of a layer of 0,2 m. GL-3 - loam of brown grey color, a
firm consistence, macro porous, subsiding soils, with particles
of calcium as veins, sometimes with inclusion of gravel and a
fine pebble up to 5 %. Capacity of a layer of 0,2-2,6 m. The
angle of internal friction is equal 19 °, cohesion intercept 33
kPa, the module of deformation of 7,4 MPa.GL-4 - gravel a
ground with a loamy and sandy filler in amount up to 20-30 %,
with inclusion of boulders in the size up to 300mm up to 15 %.
Capacity of a layer of 0,3-0,4 m. The angle of internal friction is
equal-36°, cohesion intercept-27 kPa, the module of
deformation of 68 MPa. GL-5 - gravel a ground with a sandy
filler up to 20-25 %. Presence of fractions: boulders - up to
12,5-29,0 %, with depth the amount of boulders is increased up
to 30,2-34,0 %, a pebble of 27,8-63,2 %, gravel - 5,5-22,8 %.
Fragments are well processed by water and have no sharp
corners. Opened capacity of a layer of 9,8-34,0 m. The angle of
internal friction is equal 41°, cohesion intercept 36 kPa, the
module of deformation of 75 MPa.
3. SPECIAL RESEARCHES OF PROPERTIES OF SOIL
Experience of design on gravel soil shows that usually
as the basic data characterizing properties of soil, values of
strength characteristics only filler are used generally. Influence
of large fractions thus aren't considered. It leads to use of the
