UDC 622.271.3:012.3.001:622.281.424

Construction and Architecture

Ph. D., Associate Professor, SerdaliyevYerdulla

Kazakh National Technical University named after K.I. Satpayev

Ph. D., Master of Mining, Yerkin Iskakov

Kazakh National Technical University named after K.I. Satpayev

Calculation and method choice barring of boards of a ditch by protecting bored piles for opening of a ditch of the Lobby station "Baikonur" subway of Almaty.

Construction lobby belongs in the open way to difficult types of works in a metro engineering as it is connected with disclosure of a volume ditch, with disclosure of developments of big section, and also with the device of a complex of the interconnected constructions. It directly lobby, and also escalator tunnel, entrances and under crossing, ventilating channels and other external networks. Construction conduct in such technological sequence not to allow a sagging of the crust surface, buildings dangerous to safety edifice and constructions, and also a sagging of underground communications of the municipal economy located in borders of a theoretical prism of a collapse of boards of a trench. Motions of the ground massif have to be minimum.

During geological researches, on the Baikonur station platform geological developments from a surface opened the 1,0-1,5 m bulk ground presented by loam to easy, dusty with roots of plants, with pebble, construction garbage, asphalt of the carriageway of roads.

Below pebble soil alluvial proluvial origins of quaternary age, low-damp, with sand-gravel filler and inclusion of well pebble rubbles by the size to 700мм to 40% from the total amount of ground of roads lies. Petrography the composition of ground is presented by fragments of granites and granodiorite gray color, fragments of quartzites and siliceous sandstones less often meet.

Pebble ground by results of the carried-out chemical analysis isn't salted and doesn't possess corrosion activity to concrete and fittings. Underwater on a station platform Baikonur aren't opened.

The lobby of Baikonur station is located near buildings of multistoried city building and streets with heavy traffic of city transport that is an additional complicating factor for construction.

In the course of construction continuous control of deformations was conducted fix also the buildings which have been close located to a ditch.

During the carried-out analysis and calculations, and also comparison of economic indicators of a pile wall and "slurry wall" shows that the pile wall is more economic at the small volumes and with a big length of a protection the "slurry in wall" is more favorable ".

In this regard, it was decided fence bored piles.

When fastening a ditch of the station "Baikonur" by protections from bored piles. On a development contour before excavation the faltering pile wall perceiving horizontal loadings is erected.

In this regard the decision to use a protection from bored piles was made.

The protection from bored piles belongs to being low-deformed types of fastening therefore the decision to apply at big loadings on a ditch brow was made. Drilling of wells under protection of clay solution or upsetting pipes doesn't cause considerable changes of tension in soil that excludes opportunity a deposit of nearby buildings and constructions.

Walls with a faltering arrangement of piles arrange in the dry coherent ground, capable to hold a vertical slope 1 ¸ 2 m high. Interval between piles for prevention of local inrushes protects a wooden inhaling.

Boring piles produce according to such technological scheme: the well is drilled, the fittings are installed, and then a well fill with a concrete mix. Thus there are more than a half of expenses of work, to time and cost it is the share of well drilling.

Driving of wells carry out boring MUSTANG 5-P4 installation. Upsetting pipes are applied to prevention of a collapse of walls of wells when drilling.

Fastening of boards of a ditch are made from bored piles ∅168х8мм, with filling of these piles with class B25 concrete. Piles settle down at a slow pace 500мм on an axis.

Upsetting pipes are left in soil they entered into a design of piles. Upsetting pipes plunge into soil by means of vibration in the course of drilling.

Drilling of wells of advancing fastening is made in a mode of shock and rotary drilling by the MUSTANG 5-P4 drilling rig, direct washing of wells with water when drilling wells of long 10500 mm.

Limit tolerances of a tilt angle of a well concerning D=± 1,5° vertical.

Limit tolerances of length of a well of rather design D=+200 mm.

Bored piles with an upsetting pipe are applied in unstable ground: gravel and pebble deposits, rubbles.

The simplified scheme of a construction of piles: leading well drilling; immersion by a mechanical or pneumatic hammer of a pipe; well cleaning inside to the basis; concrete acceptance.

Purpose of these piles – the bases and a protection of ditches.

Piles on length reinforce longitudinal cores of a periodic profile with a step no more 200мм.

Cross fittings from steel with a diameter from 6 to 12мм install with a step 150¸200мм.

At installation of a framework the fittings sheeting with a concrete layer thickness not less 50мм has to be provided.

Wells concrete a cast concrete mix with a cone emptying 160¸200мм free dumping.

Concreting by free dumping of a concrete mix in a well carry out in the absence of water and length of piles to 10м.

For association of separate piles in walls arrange longitudinal belts from steel profiles and the ferroconcrete beam concreted on a place. The ferroconcrete beam is at the same time single pour pile head and a side protecting a ditch from storm waters.

Piles in dimensions of designs of foot tunnels of entrances to a lobby are subject to partial dismantle (extraction). In this regard in the project it is provided that the piles which are subject to partial dismantle (extraction) aren't filled with concrete and fittings on height of the site which is subject to partial dismantle. On height of the site which is subject to partial dismantle, a pile are filled with local ground.

On the basis of the carried-out calculations, for a choice of the most optimum choice of fastening of boards of a ditch of the Lobby of station "Baikonur, the solution of a choice construction by a method of bored piles was made. That in the conditions of construction in difficult mining-geological conditions is the most optimum.