11.2. Dismantling

Demolition of buildings and structures is carried out by dividing them into parts (for subsequent dismantling) or collapse. Wooden buildings are dismantled, discarding elements for later use. When disassembling each detachable precast element must first be loosened and take a stable position.

Monolithic reinforced concrete and metal structures are disassembled according to a specially designed demolition scheme that ensures stability of the structure as a whole. Partitioning into disassembly units begins with opening the reinforcement. Then the block is fixed, after which the reinforcement is cut and the block is broken off. Metal elements cut off after unfastening. The maximum mass of a reinforced concrete disassembly unit or a metal element should not exceed half of the lifting capacity of the cranes with the greatest departure of the hook.

Prefabricated reinforced concrete buildings dismantled according to the scheme of demolition, inverse installation scheme. Before disassembly, the element is freed from connections. Prefabricated reinforced concrete structures that are not amenable to element-by-element separation, dismember as monolithic.

Demolition of buildings and structures is carried out with hydraulic hammers, jackhammers, and in some cases - with excavators with various attachments - ball and wedge hammers, etc. Vertical parts of the structure should be brought inwards to prevent debris from scattering across the area.

Collapse is also carried out in an explosive manner. After clearing, a general layout of the construction site is made.

With the release of the construction site for new construction, reconstruction and expansion of industrial enterprises, overhaul of residential and cultural and residential buildings and in some other cases perform work on dismantling existing buildings and structures or their individual elements. The disassembly process consists of two stages - preparatory and main. At the preparatory stage, the contracting organization, on the basis of the design and estimate documentation (including the PIC for the dismantling of buildings), together with the representatives of the customer and the design organization, makes an inspection of the buildings being demolished. During the survey determine: the condition of buildings and structures as a whole and their elements; production methods and scope of work; the release of material and structures from disassembly, suitable for subsequent use; reliability of disconnection of engineering networks; factors that may adversely affect the work; measures to preserve nearby buildings; dates of commencement and completion of work, etc.

Based on the survey results, the contractor develops an outage plan for building disassembly. The construction work includes a construction general layout of the demolished structure, diagrams and flow charts of work execution, work schedules, methods and sequence of work, methods for temporary fastening of structures, erection cranes, construction machines, mechanisms and transport, rigging equipment for hooking elements, scaffolding, scaffolding and stairs , needs for vehicles and construction vehicles, etc. The special section of the CPD contains measures to ensure the safety of work, including the protection of danger Second area of ​​the demolished facility, installation of warning signs and signal lights, additional briefing on the work on the construction of the parsed, the prohibition of dumping of materials, designs and construction debris from the walls and ceiling, suspension of work when creating an unsafe situation and others.

At the main stage of dismantling various buildings, mainly manual, semi-mechanized, mechanized and explosive methods are used.

Manual disassembly or destruction is the most time consuming. It is carried out using hand tools, crowbars, wedges, sledgehammers, picks, skarpels, etc., as well as gas-cutting installations. This method is used for small amounts of work or in cases where other methods can not be used.

The semi-mechanized method is based on the use of pneumatic and electrified tools: jackhammers, shovels, pneumatic concrete breakers, mechanical saws, winches, jacks, etc. The method is widespread. However, it is time-consuming, expensive, besides, the production of work is accompanied by great noise and dust.

In the mechanized way of work performed with the help of machines and mechanisms. The method of impact destruction of structures by a ball or wedge hammer, suspended on cables to an arrow of a self-propelled crane or an excavator, has become most widespread. Tractors or bulldozers are used for the collapse of stand-alone structures or sections of buildings cut off from their main part: the structures in the upper part are pre-tied with steel cables, tied to mechanisms and pulled before tipping over and destruction. In this case, the angle of elevation of the cable in relation to the horizon should be no more than 20. . Bulldozers are also used for moving and hilling construction scrap and debris. Compared with semi-mechanized, this method is more productive and rational when dismantling old buildings and structures.

The explosive method is based on the use of explosive energy. For the destruction of buildings, blast-hole explosive charges are used, which are located on the same level at the base of the building along its perimeter (not less than 0.5 m from the ground surface), thus forming a continuous slaughter. As a result of the explosion, the building collapses and collapses on its foundation. Before the explosion, the building must be freed from all wooden structural elements (rafters, floors, partitions, floors, doors, windows, etc.). Concrete and reinforced concrete structures explode into crushing. Depending on the size of the structures and structures apply overhead, blast-hole, borehole or chamber charges. The explosive method is the least time consuming and most economical.

For the destruction of monolithic structures can be applied electro-hydraulic method. In contrast to the explosive method, an electro-hydraulic does not produce a blast wave, there is no scatter of fragments. This is especially important in the production of works in the territory of the existing enterprise or inside the production premises.

For the cutting of concrete and reinforced concrete, burning holes in it and strab, a thermal method of destruction is used. The method is based on the use of a powerful heat source in the form of a gas stream (“oxygen spear”) or an electric arc (graphite or carbon electrodes).

When dismantling or destroying buildings, structures, and individual structures, the combined method is most often used, in which some structural elements are disassembled by hand, others mechanized, third by explosive, etc. For example, manual demolition of structures is recommended when demolishing a single-storeyed frame building with brick walls with the exception of walls, which should be dismantled in a mechanized way, and foundations destroyed by an explosion.

When reconstructing or expanding existing enterprises, sometimes there is a need to disassemble individual structural elements, such as ceilings, partitions, walls, floors, foundations, columns, etc. Under these conditions for disassembling each structural element, it is necessary to develop an outage where borders of the danger zone, as well as measures to relieve the load from the structure to be disassembled, ensuring the stability and safety of the rest of the building elements, etc.