Transport and loading and unloading operations in construction have a large specific gravity, they account for over 42% of the total labor intensity of construction and installation works. Therefore, it is very important to use mechanization as widely as possible, and in some cases complex mechanization, in the performance of these works.
Complex mechanization of loading and unloading operations. involves mechanized loading and unloading of goods and containers with a minimum number of reloads, with the lowest cost and labor intensity, while maintaining the original quality of goods in transit.
Transport in relation to the object under construction is divided into external and intra-construction; the latter is used within the construction site for the delivery of materials and structures to workplaces (to the crane operation area).
For the production of loading and unloading operations, mechanisms are used: tower and boom cranes (caterpillar and pneumatic wheels), forklifts, universal bucket loaders, etc. The use of an integrated system of containerization and palletizing of goods is effective, as well as the delivery of prefabricated structures in enlarged units using special vehicles in a strict technological their installation sequence.
Handling equipment used for loading and unloading operations must meet the requirements of GOSTs, and load handling equipment must have a stamp indicating the maximum load capacity. Organizations developing load gripping devices must have special permits from the supervisory authorities (Gosgortekhnadzor, etc.).
Loading and unloading operations are classified as the most labor-intensive, which encourages the widespread use various means mechanization that reduces the number of workers, reduces the downtime of vehicles and protects goods from arbitrary fall. Prefabricated reinforced concrete structures for their capture, lifting and delivery to the place of unloading are equipped with load-gripping loops or special devices (holes; protruding consoles, etc.).
Specialized vehicles are used to transport long structures or structures that need to be laid and strengthened during transportation in special ways: trusses, beams, panels, floor slabs, sanitary cabins, etc. Most often, a road train includes a truck tractor and specialized dissolution semi-trailers.
Wall panels are transported on backbone, cassette and platform panel carriers. Spatial load-bearing frame of backbone panel carriers has a trapezoidal cross-section and a small loading height. More versatile are cassette panel carriers. Rafter and sub-rafter trusses are transported by semi-trailers. Floor slabs and coatings, as a rule, are transported on slab semi-trailers; beams, respectively, on bulk carriers.
Structures and products whose dimensions exceed the allowable dimensions (width - 2.65 m, height from the level of the carriageway - 3.8 m) are considered oversized and are transported according to special rules, with the permission of the traffic police.
Structures, as a rule, have two support points, under which wooden linings of rectangular section are laid. Structures with one-sided reinforcement (slabs and beams) are transported in the working (design) position - the working reinforcement is at the bottom. Panels that are not designed to work in a horizontal position, as well as products made of lightweight concrete with a thickness of less than 200 mm, are transported in a vertical position ("on edge"). The columns are transported in a horizontal position - flat. Trusses 18 and 24 m long are transported in a vertical (design) position, and 30 m long - in an inclined position: they are supported on wooden linings and fixed in the knots of the upper belt. Wall panels without working reinforcement rest on linings spaced in 0.5 m increments. They are transported in a vertical position, fixed on both sides; panels in an inclined position are fixed on one side.
The used loading and unloading mechanisms are divided into those operating independently of vehicles (self-propelled automobile and pneumatic wheel cranes - loaders, pneumatic wheel and caterpillar excavators with crane equipment, universal loaders, mobile and adjustable belt conveyors, pneumatic or auger unloaders, mounted mechanical shovels, etc. .) and included in the transport facilities (dump trucks, vehicles with self-loading platforms, vehicles with devices for self-unloading, etc.).
Loaders have received the greatest practical application in construction. With their help, up to 15-20% of all volumes of loading and unloading operations are now performed, which is explained by their versatility and high mobility. Universal shovel loaders, auto loaders and multi-bucket loaders are widely used. Loaders are front, semi-swivel and full-swivel. In loading and unloading operations, front loaders are most often used, equipped with quick-detachable buckets, crane equipment, fork lifts, jaw buckets and other working bodies. Due to their versatility, mobility and high cross-country ability, shovel loaders are effectively used in small-scale dispersed construction, as well as in lifting and transport operations within the construction site (transportation and supply of packages, wall materials, buckets and bunkers with concrete, mortar, etc.) . Bucket loaders are used for loading bulk and fine bulk materials.
Forklifts, like construction loaders, are equipped with interchangeable working bodies (beamless boom, bucket, jaw gripper, etc.), but are used mainly on hard-surfaced sites - at on-site warehouses or construction industry enterprises. Mobile belt conveyors are used for loading loose, lumpy and small-tonnage cargo. To unload powdered and bulk materials from covered wagons, mechanical shovels are used, operating on the principle of pulling scrapers, and pneumatic unloaders are used to unload cement.
Self-unloading vehicles are equipped with devices for craneless self-unloading of long loads, containers and hydraulically controlled jib cranes. The use of such tools is especially effective for servicing dispersed objects with small volumes. construction works, which, in particular, is typical, for example, for agricultural construction. Self-unloading vehicles also include cement trucks, consisting of an autotractor, a tank and a suction unloading device.
Tank unloading is based on the property of aerated cement (saturated with air) to flow like a liquid.
Pipes from gondola cars are unloaded either to a warehouse, and then to a pipe carrier, or immediately to a pipe carrier, which is more efficient. Pipes are unloaded by automobile and pneumatic wheel cranes of the required carrying capacity. When unloading pipes on pipe trucks, the latter are installed parallel to the track opposite the car, and the crane is installed between them. When unloading pipes from gondola cars, end grips are used, consisting of two or more ropes with hooks at the ends. In order to avoid damage to the edges of the pipes, the hooks are provided with sponges made of soft material. For temporary storage of pipes, rail, road and base warehouses are organized, which are high-row and low-row, up to 8 and 3 m high, respectively.
High-row ones are more efficient, since they provide more high level mechanization of loading and unloading operations, the storage area is reduced and the quality of pipe storage is improved.
When loading and unloading insulated pipes and sections, it is necessary to take measures to ensure the safety of the insulation coating. It is not allowed to hit the pipe against the pipe, about the racks of trailers, dropping rigging devices onto the surface of the pipes, etc. Soft grippers (towels, etc.) should be used for their slinging, and the booms of pipe-laying cranes should be wrapped with shock-absorbing rubber gaskets with a thickness of at least 20 mm.
Schemes of complex mechanization of loading and unloading operations can be as follows. Cars with finished parts, structures, containers and packages are fed under the crane hook with their transfer to the installation site or to the area where these materials or semi-finished products will be used. Bulk cargoes in a quarry or in a warehouse are loaded into a dump truck by a universal or frontal shovel loader. The dump truck unloads aggregates into the warehouse of the construction concrete plant, from where they are fed to the batchers by a scraper installation. Cement is usually delivered to the site by cement trucks with a capacity of up to 60 m 3 , unloaded by a special air device using compressed air.
Covered wagons and gondola cars are unloaded by screw pneumatic unloaders with a capacity of up to 90 t / h, which supply cement into the hatch of a cement truck with a carrying capacity of 10 to 22 tons. The cement unloaded from them is fed through the pipeline into storage silos, and then to batchers of concrete mixers.
To organize the transportation of bulk construction cargo, it is necessary to use specialized containers and packaging equipment for technological purposes, which are circulated in a closed system: the supplier is the construction site. The range of goods for delivery in containers and packages is quite extensive - these are bricks, parapet slabs, window and door blocks, pipeline blanks for internal plumbing systems, parquet and boards, glassine, roofing felt, electrical materials, glass, heat-insulating materials, facing products, paints, etc. . (more than 70 items).
Containers and packages are loaded by rolling cargo from the unloading platform of a vehicle or by forklifts equipped with a set of interchangeable working equipment, including grippers for pipes and rolled materials. Containerization and packaging can dramatically reduce the complexity of loading and unloading operations, improve the use of mechanization and ensure better safety of transported goods. Containers and packages can also be unloaded by special self-unloading vehicles. Warehouses of reinforced concrete plants, central pipe-welding or pipe-insulating bases are usually equipped with gantry or overhead cranes that unload vehicles and wagons.
The choice of a more rational option for complex mechanization of loading and unloading operations is carried out according to specific indicators technical and economic efficiency.
Loading and unloading works
The organization of loading and unloading operations is understood as a set of measures that determine the place, composition, sequence and duration of loading and unloading operations, the type of goods being processed, the methods of their storage and slinging, the types of lifting and transport vehicles used and the methods of their installation relative to each other and the transported cargo, as well as the composition of the link of workers participating in loading and unloading operations.
Places where loading and unloading operations are carried out are called cargo handling points. Each such point differs in cargo traffic. Freight traffic is characterized by the type of cargo, the direction of its movement and the amount of cargo passing through a given point per unit of time.
Cargo processed by truck cranes, according to the method of formation of a cargo space, are divided into piece, packaged and transported in containers or containers.
Classification of materials, products and structures according to the method of formation of a package
Schemes of movement of goods depend on the organization of their delivery to the place of consumption. In construction, goods are delivered to the facility according to a scheme that provides for four points of cargo processing: a plant for the production of materials and products - a base warehouse - an assembly site for structures - an on-site warehouse. For a number of objects, for example, in residential and cultural construction, goods with a high degree pre-fabricated products are delivered, bypassing the base warehouse, assembly site and on-site warehouse.
Cargoes from the first point of cargo processing to the second are delivered by rail and road, and to the assembly site and from it to the on-site warehouse - by road.
With this scheme, four cargo flows are formed in the direction of movement of goods: - loading materials onto rail or road transport and unloading from it to the base warehouse or reloading materials from railway transport for automobile; – unloading materials from road transport to the on-site warehouse; – reloading of materials from one place of storage to another during the construction of the facility.
The operations that make up the loading and unloading operations are divided into main and auxiliary. The main operations include the capture of cargo and its supply to the vehicle or to the place of storage. Auxiliary operations include operations that are not included in the process of moving cargo: securing and releasing slinging devices, aiming cargo or laying them in the required position, signaling to the driver, preparing vehicles, storage areas, linings, gaskets, etc.
At loading and unloading operations, rational conditions and methods for performing auxiliary operations should be provided: the most advantageous labor methods for manual work, the coherence of the joint actions of the link of workers, rational designs of devices (for example, load gripping devices, gaskets, lining stairs).
The main form of labor organization in loading and unloading operations is a specialized unit consisting of a crane operator, a slinger, and a rigger.
Loading and unloading cargo consists of a series of sequential labor techniques. At the signal of the slinger, the driver turns the crane to the place where the load is located, lowers the hook with a traverse for slinging the load. Convinced of the reliability of the loops and checking out the hooks of the sling for them, the rigger gives a signal to the driver to lift the load. If necessary, the worker, having attached the brace to the load, accompanies it to the place of laying, where, at the signal of the rigger, he directs and lowers the load into place.
The composition of the link, the content of operations and the duration of the execution of each of them depend mainly on the type of cargo and working conditions. For example, loading and unloading of floor slabs is performed by a link consisting of a truck crane operator (5th category), a slinger (4th category) and a rigger (3rd category).
The amount of cargo passing through this point of cargo handling per unit of time (hour, shift, day, etc.) depends on the amount of work at the facility, the location of the place where the cargo goes, the rate of construction of the facility, the level of organization of work used at it types of machines.
Automobile cranes used in loading and unloading operations must have a lifting capacity corresponding to the weight of the package. As a rule, automobile cranes process cargoes, the mass of which is indicated either on the package or in the accompanying technical documentation. When loading and unloading goods of unknown mass, the mass of one package is determined in advance. The approximate weight of one piece of the most common cargo is given in Table. fourteen.
Departure A and lifting height I of the hook of truck cranes are determined depending on the size of vehicles and warehouses, taking into account the rational scheme for installing the crane at the point of cargo handling (Fig. 156) according to the formulas.
Rice. 156. Schemes for determining the departure and lifting height of the hook when loading and unloading materials from rail (a) and road (b) transport into a pile, from rail transport into road transport (c), from one pile to another (d),
Formulas for calculating the loading height of cars (y - volumetric mass of cargo, t / m3)
The indicators included in the above formulas are determined from various sources: current GOSTs, regulatory and technical documentation for the dimensions of vehicles, cargo and slinging devices, as well as in accordance with the norms for warehousing cargo and the rules for safe handling of lifting and transport operations.
The loading height of vehicles hn and the height of cargo slinging Ac + r are determined by calculation. The loading height of cars K depends on their carrying capacity and the volumetric mass of the cargo. With a given carrying capacity of the car, the height of its loading is the greater, the lower the volumetric mass of the load.
The installation of the crane relative to vehicles and places of stowage of goods must ensure full or maximum use of its lifting capacity in all areas of the working
zone at the minimum radius of rotation of the turntable. In this case, it is necessary to take into account the minimum allowable approximation of hoisting machines to vehicles, warehouses, buildings and the accepted sequence of filling the warehouse with materials.
The scheme of cargo placement at the cargo handling point is determined by the size of the warehouse, the type and method of storage of materials, products and structures on it. In the on-site warehouse, the scheme) for the placement of goods depends, in addition, on the technology of erecting buildings and structures.
Rice. 157. Layouts reinforced concrete products in stock:
1 - columns, 2 - slabs, 3 - beams, 4 - crane, 5 - trusses, 6 - foundation pads
The dimensions of the warehouse and the number of stacks on its territory are set in such a way as to create a stock of materials for the construction and installation work at the facility within 5-7 days. The dimensions of the stack depend on the dimensions of the cargo, and the number of rows in the stack horizontally and vertically is determined by its stability and the bearing capacity of the base. At the on-site warehouse, the stacks are located in the area of the assembly crane, taking into account the convenience of unloading vehicles. The long side of the stack is placed parallel to the access roads, which deliver materials and structures to the warehouse, which reduces the hook reach.
Each stack must be located in the area of the main assembly crane and contain the number of elements sufficient to serve the entire working area of the assembly crane. Between the time sheets in the warehouse, it is necessary to arrange driveways and passages with a width of 3.5 and 1.5 m, respectively. One of the possible layouts for the placement of reinforced concrete elements during their storage in a warehouse is shown in fig. 157.
Ways of stacking goods in a pile depend on their purpose, methods of slinging and installation. The position and method of supporting the loads should not cause overstressing of the material (Table 18, Figures 158 and 159). When laying flat reinforced concrete elements, the working reinforcement should be facing downwards. Goods in the warehouse are placed so that their marking is easily read from the side of the aisle or driveway, and the mounting loops are facing upwards. Each element of the load must be supported by two inventory linings, which are located across the element. Vertically, these linings should be strictly one above the other.
The method of organizing installation work is determined by the type! object, place, method of laying in the design position and type! structures to be mounted, the content, sequence and duration of the installation operations, the machines used and their arrangement relative to the building and the warehouse, the composition of the link of workers. Installation of structures at the facility is carried out in a certain sequence, which ensures the preparation of the relevant sections for after installation work.
Structures mounted on objects are divided according to the type of material, functional purpose, the principle of formation of the mounting unit and the mounting method. The most common in the practice of installation work are structures made of reinforced concrete, concrete, rolled metal, sheet metal, wood and synthetic materials. An assembly unit can be piece elements (purlins, crossbars, columns, slabs), large-sized prefabricated parts (panels for one or two rooms, sanitary cabins and blocks), as well as elements that have undergone preliminary enlargement assembly.
Methods of installation of structures depend on the type of installation units and the sequence of their installation in the design position.
According to the degree of enlargement of structures, three methods of installation are distinguished: by individual elements, blocks of structures and structures as a whole. The first method is the most widely used. It is used in the installation of foundation blocks, columns, beams, slabs, trusses, etc.
Depending on the sequence of installation of mounting units in the design position, differentiated (separate) and integrated mounting methods are distinguished.
With a differentiated method, the installation begins with the laying of foundation blocks and pillows, the installation of columns, then the installation of wall elements, beams, floor slabs, trusses, and roof elements is sequentially carried out. With this installation method, the crane can move along the span (in the middle or edge), across the span, outside the building under construction along its perimeter. The way of moving the crane is chosen depending on its carrying capacity, reach and lifting height of the hook, design and planning solutions of buildings, mass of mounting units. Moving along the middle of the span, the crane can install up to four or more columns from one place, which reduces the number of its movements. With large spans, the technical capabilities of the crane are often insufficient for the installation of adjacent columns, and in this case it moves along the edges of the span, working at a minimum reach. Thus, the number of its permutations increases. When moving across the span, the working path of the crane is much shorter than in the case of its movement along the span, but the total time for moving the crane from one span to another increases. The most effective is to move the crane outside the building or structure along its one, two or all sides, but this scheme can only be used when installing one-story residential buildings and buildings for cultural and community purposes, as well as small detached structures with a width corresponding to the useful reach of the hook.
With the complex method, opposite structures are simultaneously mounted within the working area of the crane. This method is most commonly used in prefabricated buildings, where a crane simultaneously lays foundation blocks, installs external wall panels and internal partition panels, and then lays floor slabs on top of them.
Rice. 160. A possible scheme for moving a crane during the installation of structures of an agricultural building
Data on the accepted method of installation of structures is contained in the project for the production of installation work, which is drawn up according to the working drawings for the construction of buildings and structures in accordance with the "Instruction on the procedure for compiling and approving projects for the organization of construction and projects for the production of works" (SN 47-67). Sample projects installation works in each specific case should be tied to local conditions, based on data on the availability of cranes, the location of storage sites for mounted structures.
For example, it is required to select a movement scheme and a crane type for a differentiated method of mounting foundation blocks and columns with the following initial data: building type - one-story agricultural purpose; number of spans - 3; span width - 8 m; column pitch - 6, column height - 6 m; the length of the building along the axes of the extreme columns -42 m; weight of the foundation block - 2, columns - 1.2 tons; the location of the place of storage of blocks and columns - in the area of the crane.
Rice. 161. Scheme of organization of the workplace during installation under the "ground part of a residential building: M, M2, M3 - installers,
1 - sand box, 2 - block storage, 3 - crane, 4 - mounted block, 5 - darning, 6 - assembly crowbar, 7 - level, 8 - tool box, 9 - shovel, 10 - mounted blocks, 11 - slope
When choosing a crane for mounting columns on laid foundation blocks, it is necessary to determine the height of its lifting simultaneously with the hook's flight. Taking into account the length of the slings of 1 m, the lifting height of the hook when installing the column in the design position is 4.5 m, which corresponds to the technical capabilities of cranes with a lifting capacity of more than 4 tons.
Installation work is carried out by a complex team of workers, consisting of assemblers, slingers, riggers and crane operators. In order to maximize the use of cranes in time during the day, installation work is organized in two or three shifts. The brigade is divided into units that work in shifts. Links in which the foreman does not work are led by the link.
During the first and second shifts, the installation of structures is carried out directly, in the third shift, the parts arriving at the on-site warehouse are unloaded and materials are delivered to the floors for work inside the building. When mounting "from the wheels", when there is no need to perform loading and unloading operations, installation work is carried out during all three shifts.
At certain stages of the construction of buildings and structures, the organization of work can be changed: for example, in the first shift, sanitary work is performed or technological equipment is installed, and during the next two, structures are mounted.
A possible variant of the advanced organization of labor is shown (Fig. 161) on the example of the installation by a truck crane of the underground part of a residential building from prefabricated elements.
The workplace of the installers is the assembly grip, the dimensions of which are established by the project for the production of works, based on the need to ensure parallel conduct of sanitary and electrical work in compliance with safety regulations.
A link (three workers of the 4th, 3rd, 2nd categories and a machinist of the 6th category) mounts the foundation elements on a pre-prepared base. First, pillows are laid, along them - corner and lighthouse blocks. Intermediate blocks begin to be laid from the grip that is most distant from the crane, located in the zone of its work. Further, the installation is continued at the sites for installing wall panels of the basement floor, where the work is carried out by a link of four installers of the 5th, 4th, 3rd, 2nd categories, a machinist of the 6th category and an electric welder of the 5th category. Installation of wall panels and partitions begins with preparing them for slinging. During this time, two installers at the installation site of the panel arrange a bed of mortar, after which the driver brings the panel there, and three installers, using mounting crowbars, install it in place according to the marked risks.
Floor slabs are laid by four installers who were previously engaged in the installation of foundation elements and panels. When laying the part in the design position, the driver must lower it smoothly, using the landing speeds of the load lifting mechanism.
To Category: - Organization of the work of truck cranes
Classification of construction cargo and modes of transport. Transportation of building materials
During the construction of any building or structure, certain transport and handling operations are performed related to the delivery of various materials, semi-finished products and products from the places of manufacture to the construction site. The elements delivered for the construction of the structure are called construction materials.
Depending on the physical and geometric characteristics, building materials are divided into 9 types: bulk (sand, crushed stone, gravel, soil); powdered (cement, lime, gypsum, chalk); doughy (concrete mixture, mortar, lime dough); small pieces (brick, blocks, etc.); piece (window and door blocks, floor slabs and coatings); lengthy (trusses, timber, columns); liquid (gasoline, lubricants); large-volume (sanitary cabins, block rooms, etc.); heavy (reinforced concrete elements of considerable mass, construction machines etc.).
Based on the variety of construction cargoes, a wide variety of means of their transportation have been used in construction, and appropriate means of loading and unloading them have been developed.
Transportation of building materials is carried out by vertical and horizontal transport.
Vertical transport is designed to perform loading operations at the factories supplying building structures, unloading operations during the acceptance of materials and products arriving at the construction site, during the transportation of goods vertically from the ground to the place of work.
Horizontal transport they transport construction goods from the place of their receipt to construction sites and directly at the facilities themselves, if not individual buildings are being erected, but a whole construction complex.
Horizontal transport in relation to the construction site is divided into external and object. By external transport, building materials, structures are delivered to the construction site from supplying plants, quarries, warehouses to the facilities under construction. Object transport move construction cargo within the construction site.
In construction, the transportation of goods is carried out by all types of modern transport. The choice of vehicles depends on the type of cargo being transported; dimensions and weight of structures and parts; method of transportation; dimensions of spatial elements; transportation distance; permissible speed of cargo transportation; method of unloading cargo; type of road, slopes, outdoor temperature and transported cargo; transportation conditions.
Vehicles are:
- cyclic action: a) rail - railways of normal (broad) or narrow gauge; b) trackless - automobile and tractor;
– continuous action – hydraulic; conveyor (with the help of a conveyor) and suspended.
Vehicles are selected on the basis of their technical and operational indicators (carrying capacity, possible speed of movement, productivity, road requirements, coverage, cost of operating vehicles and roads, ease and reliability in operation and the possibility of using to move other goods); conditions in which they will be used (the relief of the construction site, the dimensions of the structure in the plan and the relative height position of cuts and embankments, volume earthworks, deadlines, operating parameters, availability and condition of roads, etc.).
Automobile transport widely used for the delivery of construction materials to the construction site. In construction, vehicles with a carrying capacity of up to 12 tons and trailers for caterpillar tractors with a capacity of 9–12 m 3 are most common. This is due to the possibility of their wide application for the transportation of various materials, a large range of carrying capacity, and a relatively simple road design.
Tractor transport used to deliver goods over short distances and in case of off-road. Advantages: high productivity, the ability to use on objects with different volumes of work, less demanding on roads and dependence on weather conditions in comparison with road transport, the ability to use on steep slopes (up to 0.15).
Disadvantages of tractor transport: low travel speeds, limited use for long hauling distances. The economical hauling distance, when caterpillar tractor transport can compete with automobile transport, does not exceed 600–800 m.
Railway transport is mainly an external transport for transportation over long distances.
Railways the construction site is arranged with a wide gauge 1520 mm wide, if railway transport is provided for in the project of the enterprise under construction; as well as with a large volume of cargo delivered by him to the construction site (more than 1 million tons per year). Narrow-gauge roads with a width of 750 mm are used when transporting goods from quarries to a construction site, if for some reason it is impossible to use more efficient modes of transport - cars, trolleys, long-range conveyors.
The use of railway transport is limited by the high cost of the railway track, as well as the track conditions: maximum slopes - 0.03–0.05; curvature radii for wide gauge - 200–300 m, for narrow gauge - 60–100 m.
Special modes of transport
Specialized vehicles are designed to transport certain categories of goods: concrete mix, mortar, powdered building materials, large-sized reinforced concrete structures, etc.
For bulk transportation of powdered materials (cement, lime, gypsum, etc.), cement trucks equipped with self-unloading devices are used.
Large-sized reinforced concrete structures are transported mainly by road trains, consisting of an automobile tractor and specialized trailers and semi-trailers.
Depending on the type of transported construction cargo, semi-trailers are used: plate carriers, bulk carriers, panel carriers, farm carriers, sanitary cabin carriers, block carriers.
Special types of transport include vehicles for technological purposes, in which the processes of transportation are combined with the technological processing of this construction cargo:
- truck mixers - they simultaneously carry out the processes of preparation and transportation of the concrete mix to the construction site;
- truck-mounted concrete pumps - combine the transportation of the mixture over long distances and its laying;
- concrete trucks - combine the transportation of the mixture and its mixing.
Of the special types of (in-building) transport, belt conveyors, cable cars and pipelines are used.
Belt conveyors are most widely used in factories of reinforced concrete products (concrete products) for the transportation of aggregates, concrete mix, small-piece materials (bricks, etc.).
Suspended rope transport is used to deliver construction materials in conditions of rugged terrain and water barriers.
Pipeline transport is used to deliver some building materials: soil washed out by water, concrete mixture, mortar for plastering, cement, etc. are moved through pipes.
Loading and unloading work at a construction site
playground
Loading, unloading and warehousing of materials are the most time-consuming in the overall process of moving goods. In order to reduce manual costs in loading and unloading operations and to facilitate heavy labor, it is necessary to increase the degree of mechanization of these works.
The organization of loading and unloading operations should ensure their comprehensive mechanization with the utmost reduction in the number of transshipments. The composition of mechanized complexes includes both general construction and special machines and mechanisms.
General construction machines (tower, shooting, gantry, overhead cranes, beam cranes, excavators of various types) are used for loading and unloading piece, heavy, long and large-volume structures and materials, as well as bulk materials and containers with low-flowing materials.
The use of special loading and unloading machines determines the type of cargo.
Special loading and unloading machines are cyclic and continuous.
The most widely used in construction are various self-propelled loaders and belt conveyors.
Loaders (universal single-bucket, multi-bucket, auto-loaders) have high mobility and versatility.
Universal shovel loaders can be equipped with a bucket, fork lift, jaw gripper, dozer blade, ripper, excavator bucket and other working parts. They are used not only for loading and unloading operations, but also for moving various goods over short distances.
Forklifts, as well as universal shovel loaders, have various interchangeable working equipment - crane booms, jaw grippers, buckets, forklifts and other devices. They are used on sites with a hard surface.
Bucket loaders are classified as continuous machines and are used to load bulk materials into vehicles.
Belt conveyors are also continuous machines and are used for loading and supplying loose, small-piece and some dough-like materials (concrete mixtures) to the place of laying.
Conveyor systems consisting of individual conveyors can be several kilometers long.
In order to reduce manual labor, increase the productivity of vehicles, ensure better safety of transported goods and create conditions for the mechanization of loading and unloading operations in construction, containerization and packaging methods are widely used. The essence of these methods is to combine small-piece building materials at factories that produce them (brick, ceramic stones, small wall blocks, etc.), or at the bases of production and technological equipment (finishing materials, roofing, electrical materials, etc.) into enlarged packages or containers.
A package is a batch of cargo laid on a special pallet, a container is a multi-turn volumetric device. There are universal containers used for the transportation of various categories of goods, and special ones, designed for the transportation of a certain type of cargo. With the help of handling and transport vehicles, packages and containers are moved from the place of production or assembly to the construction site or factory.
→ Construction work
Loading and unloading works
Among the goods, the loading and unloading of which is carried out mainly by hand, are packaged construction goods. At the same time, it spoils a large number of building materials.
The main directions of development National economy and increase the efficiency of transport and loading and unloading operations in construction, it is envisaged: - to significantly improve the structure of the transport fleet, expand the production base, which ensures the maintenance of vehicles in good condition; - improve the structure and organization of construction transport management in order to massively introduce centralized transportation; – improve methods of mechanization and automation of loading and unloading operations; - create a network of mechanized cement warehouses, introduce inventory metal silos for on-site warehouses; – to develop the transportation of building materials using containers, pallets, packaging and pre-bundling of goods.
Transportation of small-piece cargo and bricks with mandatory application containers, packages and pallets will make it possible to almost completely mechanize loading and unloading operations on vehicles, reduce unproductive costs and the number of loaders employed in these operations.
In construction, specialized vehicles of increased productivity with heating of the driver's cab and engine warm-up should be widely used. For construction in hard-to-reach areas, it is advisable to expand the use of helicopters.
In order to reduce heavy physical labor in loading and unloading operations and increase the output of workers, it is planned to: - Significantly increase the use of universal loaders instead of using excavators in loading and unloading operations;
to introduce the most advanced pneumatic wheel loaders with sets of interchangeable working equipment, allowing to expand the possibilities of using loaders; - significantly expand the use of grippers and other equipment for various types of cranes (tower, pneumatic wheel, crawler, etc.).
In order to mechanize work on the intra-object transportation of materials, it is advisable to use motorized carts with a carrying capacity of 0.3-1 tons and other machines. Particular attention should be paid to the creation and implementation of means for transporting materials along the floors of buildings under construction.
Loading and unloading facilities. In the process of transporting building materials, the most time-consuming operations are loading and unloading. The mechanization of the latter is carried out by using1 self-unloading transport vehicles (dump trucks, gondola hopper cars, dump cars, etc.) and special loading and unloading machines and devices.
Currently, for the production of loading and unloading operations at construction sites, cranes, single-bucket excavators, forklifts, universal single-bucket loaders, loaders and unloaders of continuous action (bucket), mechanical and pneumatic unloaders, etc. are used.
When loading and unloading prefabricated concrete products, metal structures, equipment, materials transported in bags and containers, special loading and unloading cranes and conventional cranes designed for construction and installation work (beam cranes, overhead cranes, gantry cranes, cable cranes, tower, boom on pneumatic-wheeled and caterpillar tracks, truck cranes, etc.). Cranes can also be used for loading and unloading crushed stone, gravel, sand and other bulk materials. For these purposes, they are equipped with special gripping devices and grabs.
A forklift truck is a general-purpose loading and unloading machine designed for mechanization of handling and lifting and transport operations, mainly on hard-surfaced sites. The main working body is a telescopic lift with forks; bucket, clips for piece cargo, crane boom and other devices can serve as interchangeable equipment. Such machines are produced with a carrying capacity of 0.5; one; 2; 3.2 and 5 tons.
Universal single-bucket self-propelled loaders are equipped with a bucket for loading and unloading bulk and lumpy materials, in addition, fork lifts, jaw gripper, bulldozer blade, ripper, excavator bucket (backhoe), etc.
Single bucket loaders are available with front dumping of the bucket, with unloading to the side by turning the boom (half-turning) and with unloading back.
In urban construction, universal loaders can be used to unload and move materials over short distances, feed them to hoisting and transport machines, load receiving devices for mortar and concrete units, as well as for various auxiliary works.
Lifting capacity of loaders 0.3; 0.5; 0.8; 1.25; 2; 3.2 and 5 tons.
Continuous loaders (multi-bucket) are designed for loading bulk and small-sized materials into dump trucks and other vehicles. A bucket loader is a self-propelled machine, on the frame of which a scooping feeder and a bucket elevator or conveyor are mounted. Such machines are produced in several types, differing mainly in the design of the scooping body (raking propellers, scooping ball head, raking paws, etc.).
Mechanical unloaders (scraper shovels) are used to unload cement, lime, sand, gravel, etc. from wagons and barges. To unload cement and other powdery materials, it is more expedient to use pneumatic (suction) unloaders, which exclude the possibility of dusting the unloaded material.
Delivery of cement, lime and gypsum to construction sites should be carried out by cement trucks with their automatic loading from bunker warehouses and pneumatic unloading at the consumer.
In order to reduce the cost of handling operations, it is necessary to deliver small-piece materials to objects in containers or on pallets with mechanical unloading and feeding directly to workplace without additional overload.
Depending on the method of delivery, goods are divided into piece, bulk and bulk. All of them, in turn, are divided into other types:
piece - into small pieces (weighing up to 50 kg) - wooden and metal products, roofing and heat-insulating materials, packages, packaged pieces, etc.; building construction- panels, farms, blocks (sanitary cabins, elevator shafts); rolled metal - rod, corner, channel; and lashes of pipes; containers and packages; sets of cargoes (piece cargoes selected for the technological stage); lengthy; technological equipment and construction vehicles (when transported to facilities); forest - round wood,;
bulk - for bulk (, non-metallic materials) and blocky (rock, rubble); porous aggregates for concrete (thermolite, agloporite); powdery and dusty materials (cement, lime, ash, mineral powder); bulk - on water; semi-liquid cargoes (concrete and mortar mixes); bitumen and mastics (heated up to 200°С); binder load - hot asphalt; lime milk; liquid fuel.
The most effective form of material and technical support (MTO) of the facilities under construction is a complete set - a complete supply of materials, products and structures on time, subordinating the MTO system to the technological rhythm of in-line industrial construction. Complete delivery of goods to the construction site is calculated in advance and prepared by the production and technological equipment management service (UPTK).
There are three main types of kits: technological, delivery and transport. Technological kit - set material resources required during the construction of an object or its part (floor, section, grip), delivery kit - part of the technological kit delivered to the construction site in order of priority by date, transport kit - part of the supply kit delivered to the construction site in one flight, taking into account technological sequence of the construction of the object.
In order to improve the storage of goods in the UPTK and at the facility, as well as to increase the level of mechanization of loading and unloading operations, containers and packages are widely used during picking. A container is an inventory special reusable container for bulk piece building materials and products, adapted for mechanized loading, unloading, short-term storage of goods. By carrying capacity, containers are divided into low-tonnage (0.625 and 1.25 tons), medium-tonnage (2.5 and 5 tons) and large-tonnage (10, 20 and 30 tons). A package is an enlarged batch of piece cargo (boards, joinery, bricks). Packaged goods are transported on pallets, which by their design are divided into flat, rack and box.
In addition to the advantages discussed above, the equipment provides: centralized delivery of material resources directly to the construction site; improvement of warehousing and loading and unloading operations; reduction to a minimum of stocks of materials at the construction site; liquidation of intermediate warehouses of materials in all links construction organizations; high labor productivity.
Loading and unloading works currently continue to be very labor intensive, they employ about 10% of all workers in construction. To reduce the labor intensity of these works, they should be carried out in strict accordance with the PPR, which reflects the volume of cargo transportation by nomenclature and terms, the organization of storage facilities at the facility, the location and equipment of construction cargo unloading points, the procedure for unloading and storing main cargo.
Loading and unloading operations must be carried out in a specially designated area with an even and durable surface (concrete, crushed stone, plank) and in compliance with. It is allowed to perform work on planned ground areas that can take the design (according to the project) load from the stored goods, vehicles and lifting and transport vehicles.
Carrying out loading and unloading operations should be mechanized as much as possible. The level of mechanization is determined by the coefficient
where Q - the amount of cargo loaded or unloaded in a mechanized way 20bshch - the total amount loaded or you. loaded cargo.
A large number of specialized loading and unloading machines are used in construction. According to the principle of operation, they are divided into machines and installations of cyclic, continuous and pneumatic action, as well as machines designed to work with bulk materials in railway transport:
cyclic action machines - used when working with bulk cargo: equipped with a straight shovel, dragline, loading buckets or special loading equipment; planner excavators; single-bucket universal loaders; electric forklifts; special loaders and unloaders; cyclic machines used to work with piece cargo include various types of self-propelled jib cranes; conventional design and loader cranes; gantry loader cranes, timber loaders, electric pilers, electric hoists;
machines of continuous action - designed for scooping, transportation and loading of bulk and small-piece cargo in a continuous stream: bucket loaders; conveyors (belt, bucket belt, elevators, screws);
pneumatic machines - used for cargo processing of powdered and pulverized building materials: pneumatic unloaders of suction and suction-pressure action; pneumatic screw lifts and pumps; chamber and jet pumps; aeration installations; pneumatic bottom and tank unloaders;
machines and installations for unloading railway cars and platforms with bulk cargo: various types of unloading machines operating on the conveyor principle of loading and transporting cargo; machines and installations for restoring the flowability of frozen materials based on loosening (vibratory rippers, vibroimpact action, drill-cutting rippers) and cutting; gondola car cleaning machines; hatch lifts; shunting devices (for the movement of wagons along the unloading fronts).
