Block-section ordinary 4-storey 16-apartment - TSP

Contents

1. Source Data

2. Determination of the duration of the preparatory period and the zero cycle

3. Calculation of scope of works during pit development

4. Selection of machines and mechanisms for earthworks

5. Selection of vehicles for removal of excess soil

6. Slab design and calculation of penetrations width, excavator operating capacity

7. Description of works in winter time

8. Safety precautions for earthworks

9. Selection of formwork type, specification of formwork elements

10. Selection of concrete laying method

11. Table of labour intensity of works

12. Calculation of technical and economic indicators

13. Literature used

1. Source Data

Residential building 4 storeys, 1 block section.

Dimensions of axes in plan view 36.96 x 10 m

The building is intended for construction in Izhevsk.

Climatic region I, under the region I.

The zone is dry, normal geological conditions.

Outside air design temperature - 34˚S

Ground freezing depth - 1.80 m.

Soil - heavy loam.

Soil density - γ = 1800 kg/m3

Angle of natural slope α=63˚

7. Work in winter.

Features of excavation in winter conditions

Excavation in winter is associated with a number of difficulties. The main ones are freezing of the soil to various depths and the presence of snow cover.

When predicting ground freezing to a depth of more than 0.4 m, it is advisable to protect the soil from freezing, in particular, by loosening the soil with single or multipoint looseners.

In some places of a small area, it is possible to protect the soil from freezing by insulation with wood residues, sawdust, peat, applying a layer of foam styrene, as well as non-woven rolled synthetic materials.

To reduce the duration of thawing of frozen soil and in order to maximize the use of the fleet of earth-moving machines in warm time, it is recommended to remove snow from the strip of the future trench during the period of establishing positive temperatures.

Winter Trench Development

In order to avoid drifting of trenches with snow and erosion of soil dump during operation in winter, the pace of trenches development should correspond to the pace of insulation laying works. The technological gap between the earth-moving and insulation-laying columns is recommended not more than two-day productivity of the earth-moving column.

Methods of trenches development in winter time are assigned depending on time of excavation works, soil characteristics and depth of its freezing. The choice of the process scheme of excavation work in winter should provide for the preservation of snow cover on the ground surface until the start of trench development.

With a freezing depth of up to 0.4 m, trenches are developed as usual: a rotary or single-bucket excavator equipped with a bucket reverse shovel with a bucket capacity of 0.65-1.5 m3.

If ground freezing depth exceeds 0.30.4 m before its development by single-bucket excavator, soil is loosened by mechanical or drilling and blasting method.

When developing frozen soil using tractor rippers with a capacity of 250-300 hp, trench development work is carried out according to the following schemes:

1. When ground freezing depth is up to 0.8 m, soil is loosened with a rack ripper to the entire freezing depth, and then it is developed with a single bucket excavator. Excavation of loose soil in order to avoid repeated deafening must be carried out immediately after loosening.

2. With a freezing depth of up to 1 m, the operation can be carried out in the following sequence:

· loosening the soil with a rack ripper in several passes, then selecting it by bulldozer along the trench;

· remaining soil, having a freezing thickness of less than 0.4 m, is developed by a single bucket excavator.

The trough-shaped trench in which the excavator operates is arranged with a depth of not more than 0.9 m (for an excavator of type EO4121) or 1 m (for an excavator of E652 or similar excavators of foreign companies) to ensure the rotation of the rear of the excavator when unloading the ladle.

3. With a freezing depth of up to 1.5 m, work can be carried out in the same way as the previous scheme with the difference that the soil in the trough must be loosened with a rack ripper before the excavator passes.

The development of trenches in strong frozen and permafrost soils with a freezing depth of the active layer of more than 1 m can be carried out by a complex combined sequential method, i.e. the passage of two or three different types of rotary excavators.

First, a smaller profile trench is developed, and then it is increased to design parameters using more powerful excavators.

In complex sequential operation, you can use either different brands of rotary excavators (for example, ETR204, ETR-223, and then ETR253A or ETR254) or excavators of the same model, equipped with working elements of different sizes (for example, ETR309).

Before the passage of the first excavator, the soil, if necessary, is loosened by a heavy tractor ripper.

For the development of frozen and other dense soils, the ladles of rotary excavators must be equipped with teeth strengthened with wear-resistant surfacing or reinforced with hard alloy plates.

With a significant thawing depth (more than 1 m), the soil can be developed by two rotary excavators. At the same time, the first excavator develops the upper layer of melted soil, and the second - a layer of frozen soil, laying it behind the dump of melted soil. A single bucket excavator equipped with a reverse shovel can also be used to develop water-saturated soil.

During the period of the greatest thawing of the frozen layer (at a thawing depth of 2 m or more), the trench is developed by conventional methods, as in ordinary or swampy soils.

Before laying the pipeline in a trench, the base of which has irregularities of frozen soil, a bed 10 cm high from melted loose or finely loose frozen soil is arranged at the bottom of the trench.

When thawing frozen soil (30-40 cm) for subsequent loosening of the frozen layer, it is advisable to first remove it by bulldozer or single-bucket excavator, and then perform work according to the same schemes as for frozen soils.

Winter concreting.

Structure surface module - MP = 4.37 m-1 (ratio of the cooled surface of the structure to its volume)

Preparation of concrete mixture is carried out in heated concrete mixing plants using heated aggregates and water, which ensure production of concrete mixture with temperature not lower than required by calculation.

Transportation methods and means shall ensure prevention of concrete mixture temperature decrease below the required one.

The condition of the base on which the concrete mixture is laid, the temperature of the base and the method of laying should exclude the possibility of freezing the mixture in the contact zone with the base. When holding concrete in the structure by the method of thermos (15˚S), during preliminary heating of the concrete mixture (25˚S), when using concrete with anti-frost (15˚S) additives, it is allowed to lay the mixture on an unheated unpowered base or old concrete. The duration of vibration of the concrete mixture should be increased by at least 25% compared to summer conditions.

Unpaved surfaces of structures are covered with steam and heat-insulating materials (25˚S) immediately after concreting.

Reinforcement outlets of concreted structures shall be covered or insulated to a height (length) of not less than 0.5 m.

Before laying the concrete mixture, the surfaces of the cavities of the joints of the prefabricated reinforced concrete elements must be cleaned of snow and ice.

Concrete strength control is carried out by testing samples made at the place of concrete mix laying. It is allowed to monitor strength by concrete temperature during its holding.

10. Selection of concrete laying method.

Construction of tape foundations consists of: reinforcement works, formwork assembly, concrete mix laying and formwork disassembly.

The leading one is the process of continuous laying of concrete mixture.

There are many different methods of laying concrete in a formwork.

Recently, concrete pumps with a hydraulic drive have been increasingly used, providing smooth operation with reliable performance control, the ability to reverse and supply the mixture through lightweight concrete ducts fixed on articulated booms with telecontrol.

Mobile concrete pumps mounted on special automobile chassis are especially effective. They are used in concreting multi-storey buildings, densely reinforced structures, in cramped conditions, etc. These pumps are easy to relocate from object to object. They are supplied with thin-walled high-strength concrete ducts with diameter from 100 to 125 mm and with supply of mixture by 300 m horizontally or by 60 m vertically.

Belt conveyors are also used. When the mixture is delivered by autobeton carriers, they are supplied to a receiving vibrobunker, which ensures uniform supply to the conveyor belt. The feeding conveyor overloads the mixture on the link, from where it comes to the vibration trays or to the link probes, and then to the place of placement. Belt speed up to 1 m/s.

Boom and tower cranes installed on the brow or moving along the bottom of the pit serve the construction of foundations, masses, structures of basement floors. The concrete mixture is supplied by cranes in buckets, which are rotary and non-rotating. Rotary taverns are loaded from the car truck.

For the project, we choose the SKG40 boom caterpillar crane with a dli boom of 20 m and its maximum departure of 18 m and turning badges with a volume of 1m3.

The height of the free fall of the concrete mixture is allowed up to 2 m. With a higher height, probes are used. As the formwork is filled, the concrete mixture is compacted with depth vibrators.

Thickness of concrete mixture layer to be laid shall not exceed 1.25 of depth vibrator tip length.

At the beginning of the process of tape foundation arrangement, at crane power, rebar foundation soles are laid. Before laying of reinforcement nets to them in staggered order with pitch of 1 m fixators are fixed for creation of protective layer of concrete according to design. Then by means of crane reinforcement frames of foundation are installed, to which fixators are fixed for creation of protective layer of concrete. The frames are adjusted and temporarily fixed with the help of fixes of TsNIIOMTP. After the frames are fixed by electric welding to the sole mesh, the TsNIIOMTP retainers are removed. At 1 m linear along the perimeter of the foundations in the project we accept 1 grid and 1 frame.

The formwork is installed after the reinforcement frames are finally fixed in the design position. First, formwork of stepped part of foundation is installed and fixed, then formwork panels, previously assembled from shields. After installing several shields with a total length of 2-3 m, fights are hung on them. To the height of the shield 60 cm 1 row of fights is taken. Fights are attached to shields by means of tension hooks. On the 1 area of the side surface of the foundation, 4 of tension hooks and 10 of spring clamps are accepted, which connect the shields to each other. Formwork corners are attached by means of mounting corners. Formwork shields and its stepped part are fixed in vertical position by means of braces. With simple configuration of the foundation, 1 brace per 1 m of linear length of the foundation is installed.

Foundation decompression is performed after concrete reaches design strength. Formwork is disassembled in sequence, reverse assembly. Panels are separated, released from ties and torn from concrete. Then, using a crane, the panel is removed and the stepped part of the foundation is de-mounted.

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