cutting roadbed performed by a seam cutter for the subsequent dismantling of a fragment of the road. We carried out these road works in winter conditions at sub-zero temperature, in the amount of 260 linear meters. Roadbed where asphalt and road slabs are cutneeded to be treated with a reagent. Otherwise, the water that enters the saw blade freezes and creates ice, and this is unacceptable for the joint cutter. In summer conditions, this type of work is carried out faster.
New recipes tested by time.
Dismantling of road slabs
road slabs
and asphalt with the subsequent restoration of the road surface.
Dismantling carries out backhoe loader JCB with hydraulic hammer. Dismantled fragments of the roadway are loaded into a dump truck and immediately removed.
The total volume of dismantled concrete is 80 cubic meters. 
trench device
trenching in the roadbed. We cut the asphalt and concrete plates, knocked down concrete and removed earthen crust in the amount of 110 cubic meters. For the export of concrete, 11 containers with a volume of 20 cubic meters were needed. 
Brief conclusions
Road works cost
Road works rates
Roads are the most important means of communication between settlements. In our country, where the spaces are vast, and the range of climatic indicators for the seasons of the year is also very wide - from summer heat to bitter frosts and slushy thaws in winter - maintaining the road surface in working condition is daunting task. Only specialized companies with the help of modern road equipment can carry out road works, including measures for the repair, reconstruction and maintenance of communication lines. The quality of their implementation depends not only on the appearance and ease of use of the road, but also, most importantly, traffic safety. Most often, asphalt concrete is used for paving - a mixture of bitumen with mineral fillers (limestone, sand and gravel). Unlike a paved road, an asphalt concrete surface is much smoother, which means it is much better suited for high-speed traffic. Asphalt, due to its roughness, provides good grip for the wheels of vehicles on the road; it is easy to apply and the markup is firmly held on it. Also to the merits asphalt concrete pavement low cost, durability, maintainability and the fact that the technology of its laying makes it possible to start moving almost immediately after completion of work should be attributed. The calculation of the cost of road works is carried out, taking into account the entire range of measures to replace the road surface, as well as the materials used. The cost of road works depends on many factors and eventually becomes significant. integral part road cost. So, for example, laying a road in a swampy or vice versa mountainous area will be much more expensive than building the same road in good soils. Square meter roads with big throughput will cost much more than the same meter of a rural road. Prices for road works may include the rental of special equipment. A significant part of the cost of the road is the cost of the pavement, which varies greatly depending on the use. various materials and technologies. Currently, in connection with the use of new generation materials and technologies, for example, polymer geosynthetics, which make it possible to qualitatively change the essential properties of soils, there are new opportunities to reduce the cost of roads, pavement and, as a result, the cost of road works.
Slab laying- one of the most effective ways construction of temporary roads. It does not require large financial investments and helps in the shortest time put the cover where it is needed.
Advantages
Construction of roads by laying large reinforced concrete slabs has a number of significant advantages:
- High speed. No need to wait a few weeks until road construction will be completed.
- There is no need to use heavy asphalt paving equipment.
- You can use the coating immediately after the completion of road construction.
- After the need for the coating disappears, it is easily dismantled. Reinforced concrete slabs can be reused later.
Road construction by laying reinforced concrete slabs is carried out everywhere. Such roads can be seen at the entrance to construction sites, in areas with soft, subsiding soil, near parking lots or rural airfields.
Versatility- that's the main difference this method road construction. It is possible to lay slabs on almost any soil, which cannot be said about classical asphalting. There is no need to prepare the foundation, and the cost of renting special equipment will be much lower.
Possibility reuse- another plus in favor of the plates. In fairness, it should be noted that used stoves differ from new ones only appearance and minor chips at the joints. At the same time, they cost an order of magnitude less (an average of 40-45%).
The road surface of the slabs is not afraid of any harsh climatic conditions and no sudden temperature fluctuations. It behaves perfectly in the temperature range from -45 to +55 °C. Moreover, the addition of special admixtures to concrete can further expand this temperature Range.
material requirements
There are a number of requirements for road slabs in the organization of temporary entrances to construction sites and industrial facilities. So, in particular, the thickness of these plates should not be less than 14 cm. Inside in without fail reinforcement must be built in, and the density of the finished product must be in the range from 2.2 to 2.5 t/m. As for the form, it can be arbitrary. Some road equipment is better at laying long rectangular reinforced concrete slabs, some - square.
Depending on the operating conditions, the surface of the plates can be smooth or corrugated. Corrugated plates are more protected from ice formation. On the other hand, if caterpillar vehicles will run mainly on access roads, then there is no point in creating a corrugated surface.
Considerable requirements for road construction of access roads are imposed on the quality of concrete.. It is from this material that it directly depends on what loads the future coating can withstand and how well it will resist atmospheric phenomena. It is believed that the optimal for Russia is concrete, which has high class frost resistance (F150). If in the future it is planned to dismantle the slabs and re-construct a road using them, then it is desirable that mounting loops be built into the concrete. They must be in special recesses so as not to interfere with the movement of vehicles after laying.
Varieties of road slabs
Road slabs vary in shape and size. The size is indicated by the manufacturer in meters, and to determine the shape there is convenient system items. So, for example, rectangular plates are indicated by the letter "P", hexagonal - "W". There are also more complex names. For example, "PPB" means: a rectangular slab with two combined sides.
When carrying out road construction of temporary access roads, it must be remembered that their strength and operational properties directly depend on compliance with the technology of laying plates. As in the case of asphalting, soil preparation is far from being of secondary importance.
Soil preparation is carried out in next order:
- The upper soil layer is removed, and its surface is leveled using road equipment.
- Using the services of special equipment, a trench is torn from 30 to 50 cm deep (depending on the type of soil and the target load on pavement).
- To insure the access road from erosion and weed germination, geotextiles are laid at the bottom of the dug trench.
- A ten-centimeter layer of crushed stone is poured over the geotextile, and about 20 cm of sand is poured over the crushed stone.
- The sand cushion is poured with water.
- The soil is carefully compacted.
For tamping the soil, you can use the services of special equipment with a vibrating plate. If you need to cover with tiles large area, it is better to use a roller. Do not forget to control the level of the ground during the tamping process (for this purpose, use a level and a rope beacon).
After the surface is tamped, the laying of reinforced concrete slabs can begin. If their size does not allow you to manage the services of existing special equipment, you can resort to renting crane on wheels. To avoid distortions, the first row of road slabs is always laid along the stretched cord.
During the construction of access roads, reinforced concrete slabs can be laid with a gap or close to one another. Sand is poured into the remaining cracks. In order to prevent the appearance of cracks on the road surface, the seams are pre-expanded with a wet mortar, and the slabs themselves are covered with a film.
If heavy equipment is expected to travel on access roads, they need to be strengthened. There are several ways to do this. The easiest is to add at the stage of organization sand cushion cement. Often, to improve the strength characteristics of the road surface, the mounting loops of concrete slabs are welded together.
Everything collected from individual elements can be disassembled. Therefore, the dismantling of road slabs is not such a rarity, although their service life can reach several decades. This type of work is one of the stages in the construction of temporary access roads at construction sites. And the second case when disassembly of the road surface is needed is its repair.
Depending on the purpose for which the work is performed, there are features of the dismantling of road slabs and the choice of equipment used. The first case is a violation of the integrity of individual paving slabs. In most cases, the damage is minor and the plate can be used in more gentle operating conditions. But sometimes it takes complete destruction design, as it is unsafe to use it.
When arranging temporary entrances, the use of plates is multiple. Therefore, they are usually not welded at the seams and, if necessary, a truck crane is sufficient to lift them.
Features of the dismantling of road slabs on permanent roads
The main task when dismantling the pavement on the roads is the removal of only one element and maintaining the integrity of the rest. Therefore, the use of shock-dynamic method is not desirable. The vibration from the jackhammer causes imperceptible, but manifested further damage to the entire surrounding canvas. Therefore, individual road concrete slabs are removed today using new advanced equipment.
The first stage, from which the dismantling begins, is cutting the seams. They are filled sand and gravel mix and filled with mastic to be removed. Equipment such as joint cutters and hydraulic shears quickly cope with the task, coping even with durable granite stone and welded reinforcement.
If necessary complete removal pavement previously used shock-dynamic method. But at the same time there is a strong vibration, tons of dust and high level noise. Therefore, today the dismantling of road slabs is carried out in a more gentle way using the technology of impactless destruction. It is based on action. hydraulic system. Pressure is injected into the holes drilled in the slab, gradually destroying the structure. At the same time, the pressure is so high that not only concrete crumbles, but even reinforcing mesh. After that, the debris is easily removed and the freed area is ready for laying a new slab.
TYPICAL TECHNOLOGICAL CHART (TTK)
DEVICE OF TEMPORARY PASSAGE ON A CONSTRUCTION SITE WITH A COVERING OF PRECATED REINFORCED CONCRETE PLATES
I. SCOPE
I. SCOPE
1.1. A typical flow chart (hereinafter referred to as TTK) is a comprehensive organizational and technological document developed on the basis of methods of scientific organization of labor intended for use in the development of Work Production Projects (PPR), Construction Organization Projects (POS) and other organizational and technological documentation in construction .
TTK can be used for the proper organization of labor in construction site, determining the composition of production operations, the most modern means of mechanization and methods for performing work according to a specific technology.
The TTK is an integral part of the Work Execution Projects (hereinafter referred to as the PPR) and is used as part of the PPR in accordance with MDS 12-81.2007.
1.2. This TTK provides guidance on the organization and technology of work on the arrangement of temporary passage at a construction site with a continuous type of pavement made of precast concrete slabs.
The composition of production operations, requirements for quality control and acceptance of work, planned labor intensity of work, labor, production and material resources, measures for industrial safety and labor protection.
1.3. Regulatory framework for the development of a technological map are:
Standard drawings;
Building codes and regulations (SNiP, SN, SP);
Factory instructions and specifications (TU);
Norms and prices for construction and installation works (GESN-2001 ENiR);
Production norms for the consumption of materials (NPRM);
Local progressive norms and rates, labor costs norms, material and technical resources consumption norms.
1.4. The purpose of the creation of the TTC is to describe solutions for the organization and technology of work on the arrangement of temporary passage at a construction site with a continuous type of pavement from precast concrete slabs, in order to ensure their high quality, as well as:
Reducing the cost of work;
Reducing the duration of construction;
Ensuring the safety of work performed;
Organization of rhythmic work;
Rational use of labor resources and machines;
Unification of technological solutions.
1.5. On the basis of the TTK, as part of the PPR (as mandatory components of the Work Execution Project), Working Flow Charts (RTK) are developed for the performance of certain types of work (SNiP 3.01.01-85 * "Organization of construction production") for the arrangement of temporary passage at a construction site with a continuous type of coating from precast concrete slabs.
The design features of their implementation are decided in each case by the Working Design. The composition and level of detail of materials developed in the RTC are established by the relevant contracting construction organization, based on the specifics and scope of work performed.
RTK are considered and approved as part of the PPR by the head of the General Contractor Construction Organization.
1.6. TTK can be tied to a specific object and construction conditions. This process consists in clarifying the scope of work, means of mechanization, the need for labor and material and technical resources.
The procedure for linking the TTK to local conditions:
Consideration of map materials and selection of the desired option;
Checking the compliance of the initial data (volumes of work, time standards, brands and types of mechanisms used building materials, the composition of the link of workers) to the accepted option;
Adjustment of the scope of work in accordance with the chosen option for the production of work and a specific design solution;
Recalculation of costing, technical and economic indicators, the need for machines, mechanisms, tools and material and technical resources in relation to the chosen option;
Registration of the graphic part with a specific binding of mechanisms, equipment and fixtures in accordance with their actual dimensions.
1.7. A typical flow chart has been developed for new construction and is intended for engineering and technical workers (work foremen, foremen) and road construction workers performing work in the III temperature zone in order to familiarize (train) them with the rules for performing work on the installation of a temporary passages at a construction site with a continuous type of pavement made of prefabricated reinforced concrete slabs, using the most progressive and rational solutions for the organization, technology and mechanization of road construction works.
1.8. Parameters of temporary passage with precast concrete slab pavement:
Width of the carriageway for single-lane traffic - =3.5 m ;
Sub-base thickness - =0.15 m;
Track thickness - =0.17 m.
Fig.1. Cross section of a temporary road paved with reinforced concrete slabs
II. GENERAL PROVISIONS
2.1. The technological map has been developed for a set of works on the arrangement of a temporary passage at a construction site with a continuous type of pavement made of precast concrete slabs.
2.2. Work on the arrangement of temporary passage at a construction site with a continuous type of pavement made of precast concrete slabs is carried out in one shift, the duration of net working time during a 10-hour shift is:
2.3. The scope of work performed sequentially when arranging a temporary passage at a construction site with a continuous type of pavement from precast concrete slabs includes the following technological operations:
Geodetic breakdown of the passage structure;
Cutting of the vegetative soil layer, h=0.10 m;
Preparation of a natural base;
The device of the sandy, underlying layer, h = 0.15 m;
Installation of prefabricated reinforced concrete slabs;
Welding slabs and sealing seams with sand-cement mixture.
2.4. Technological map it is planned to perform the work by a complex mechanized unit consisting of: dump trucks KAMAZ-6520 (Q=20 t); soil vibratory roller DU-85 (=13 t, =15-70 cm, =2000 mm); watering machine PM-3U (=6000 l); wheel front loader Volvo L45В (=1.5 m); bulldozer DZ-42 based on the DT-75 tractor (=2.56 m, =0.8 m, =1.5 m, =95 hp); welding generator (Honda) EVROPOWER EP-200X2 (single station, gasoline, P=200 A, H=230 V, m=90 kg); truck crane KS-3577-3K (=14.0 t, =15.5 t, =14.0 m).
Fig.2. Truck crane KS-3577-3 and load capacity chart
|
Fig.3. Dump truck KAMAZ-6520 |
Fig.4. Watering machine PM-3U |
Fig.5. Volvo L45B wheel loader
A - total length 6000 mm; L - max. lifting height 4690 mm; T - excavation depth 200 mm; H - bucket unloading height, 45° 2810 mm; M - bucket reach max. height 830 mm; N - bucket reach 1650 mm; B - 5030 mm; C - 2450 mm; D - 410 mm; F - 2930 mm; J - 3395 mm; K - 3650 mm.
Fig.6. Bulldozer DZ-42
|
Fig.7. Generator EVROPOWER EP-200X2 |
Fig.8. Soil roller DU-85 |
2.5. For the device of temporary passage at the construction site, the following constructions and materials: medium-grained sand from 3 m / day, meeting the requirements of GOST 8736-93 *; reinforced concrete slabs 2P30.18-10 (size 30001750170 mm, m=2.2 t, V=0.88 m, without mounting brackets) that meet the requirements of GOST 21924.0-84; electrodes E-42, meeting the requirements of GOST 9466-75; dry, ready sand-cement mix 1:12, meeting the requirements of GOST 31357-2007.
Fig.9. General form road slabs 2P30.18-10
H=170 mm; H=1750 mm; L=3000 mm.
2.6. Work on the arrangement of temporary passage at a construction site with a continuous type of pavement made of prefabricated reinforced concrete slabs should be carried out in accordance with the requirements of the following regulatory documents:
III. ORGANIZATION AND TECHNOLOGY OF WORK PERFORMANCE
Solve the main issues related to the logistics of construction, incl. conclusion of contracts for the supply of material and technical resources, placement of orders for the manufacture of elements of prefabricated structures, parts and products necessary for the construction of an object (structure);
Get from building control Customer's main sets of working drawings with inscription "In production work" and provide them with a construction site;
Organize a thorough study of design materials containing the initial data for construction by craftsmen and foremen;
Develop WEP for "On-site preparatory work", containing decisions on the organization of construction production, technology of road construction works, to coordinate them with the General Contractor and the construction control of the Customer;
To appoint by order of the construction organization persons responsible for the safe production of work, control and quality of their implementation;
To equip the brigade (link) with workers of relevant professions and machinists of road-building machines with the necessary qualifications;
Familiarize the foremen and link leaders with the Project for the production of works, the Technological map and the technology for the production of work on the arrangement of temporary passage, as well as issue to the teams and links Orders-assignments, Calculations and Limit-fence cards for materials for the entire volume of assigned work;
To instruct members of teams (links) on industrial safety and labor protection during the performance of work;
Provide workers with personal protective equipment;
Establish temporary inventory household premises for storing building materials, tools, inventory, heating workers, eating, drying and storing work clothes, bathrooms, etc.;
Develop schemes and arrange temporary access roads for traffic to the work site;
Arrange temporary storage areas for receiving structures, building parts and materials;
Prepare machines, mechanisms and equipment for the production of work, deliver them to the facility, mount and test them at idle;
Deliver to the work area the necessary equipment, devices for safe work performance, electrified, mechanized and hand tools;
Provide construction site fire-fighting equipment and signaling equipment;
Provide communication for operational dispatch control of the production of works.
3.3. General requirements to work
3.3.1. The construction of temporary roads is carried out in order to provide access to construction sites, or in cases where the main road is closed to civil traffic for repair and construction work. A temporary road is also needed to access construction sites in wetlands or hard-to-reach places, to places of extraction of minerals, to logging. In the construction of temporary roads, road reinforced concrete slabs are widely used, which make it possible to reduce the time for the construction of entrances and ensure their durability and reliability.
3.3.2.
Temporary roads may be covered with crushed stone, gravel or reinforced concrete road slabs on a sandy base.
3.3.3. Roads at construction sites can be dead-end and roundabouts. At the end of the dead ends there must be turnaround areas with a size of at least 12x12 m (see Fig. 10).
Fig.10. Plan of intra-construction roads during the construction of ground structures
1 - ring road; 2 - dead end road; 3 - passing; 4 - turn; 5 - wide turn of the ring road
Fig.11. Scheme of dead-end and turnaround areas
Roads are laid in such a way that the distance from the road edge to the buildings (structures) under construction is at least 0.8 m, and to the edge of trenches or pits located along the roads, at least 1.5 m. At the same time, the roads themselves must be outside the prism of collapse soil.
3.3.4. The width of temporary motor roads is taken:
With two-lane traffic - 6 m (in justified cases - up to 7 m);
For single-lane traffic - 3.5 m with a widening of up to 6.5 m for unloading platforms for vehicles (for heavy vehicles - 7.0 m).
3.3.5. The length of the unloading area is assigned depending on the number of vehicles simultaneously standing under unloading, their dimensions and is taken within 15-45 m.
3.3.6.
The rounding radius of temporary roads depends on the size of the goods and vehicles used for their delivery, and is taken within 12-18 m.
Fig.12. Schemes of turns of temporary roads from slabs
3.3.7. On the construction site with an area of 5 hectares or more, at least two entrances from opposite sides are provided.
3.3.8. The width of the gates at the entrances to the construction site must be at least 4 m.
3.3.9. Each working exit from the construction site is equipped with a point for washing (cleaning) the wheels of vehicles.
3.3.10. At the entrances to the construction site, a fire protection information stand is installed with applied buildings and structures under construction and auxiliary buildings, a traffic pattern, the location of water sources, fire extinguishing and communication equipment, and a fire brigade is appointed.
3.3.11. At the intersection of temporary roads with hazardous areas traffic and safety signs must be installed. In necessary cases, signalmen are specially appointed to regulate the movement of transport and the operation of the lifting machine.
3.3.12. Roads should be provided with speed limit signs. The speed of vehicles on the construction site near the work sites should not exceed 10 km/h on straight sections and 5 km/h on bends.
3.3.13. The main difference between "temporary" and "permanent" coatings is the absence of mounting brackets, which are an indispensable element for the latter. The fact that concrete road slabs can be used several times (dismantled and installed in a new place) makes their use cost-effective. After use, the stove does not lose its performance characteristics, and the construction of temporary roads can immediately begin at a new location.
3.3.14. The installation of a prefabricated cement concrete pavement can be carried out all year round. AT winter time the laying of slabs in the road surface is carried out on the finished subgrade and base (arranged in the summer) in accordance with the requirements for the performance of work in the winter. In snowfall and blizzard, work on the arrangement of pavement is not allowed.
3.3.15. As the construction is completed, the reinforced concrete slabs of the temporary passageway are dismantled and transported to the warehouse of the construction organization for further operation.
3.4. Preparatory work
3.4.1. Prior to the start of the main work on the arrangement of a temporary passage at the construction site, preparatory work must be completed, which include:
Breakdown and fixing on the ground of the route;
Cutting, loading and removal of the plant layer of soil;
Natural foundation preparation.
3.4.2. Works on the arrangement of the passage should begin with determining the location of the building (structure) under construction and marking the boundaries of the passage in the presence of a representative of the General Contractor.
3.4.3. The geodetic breakdown of the passage at the construction site consists in designating its dimensions on the ground. The breakdown is carried out in two planes: horizontal and vertical. With a horizontal breakdown, the position of the axis is determined and fixed on the ground, and with a vertical breakdown, the estimated height of the passage. The axis of the crossing is first visually hung with stakes, giving the direction of the route, then the breakdown is corrected by measuring the distance from the building (structure) under construction to the axis and the marked points are fixed with stakes every 20 m. 0-1.5 m, installed every 10 m. The contours of the storage shafts are marked with stakes.
In order to prevent breakage or backfilling of the established road marking signs on the ground, they should be marked with pegs placed outside the earthworks. After the completion of the construction of the passage, the established breakdown is removed.
The work performed on the geodetic breakdown of the temporary passage at the construction site must be presented to the representative of the Customer's building control for technical inspection. In the absence of defects, and also after the elimination of deficiencies, it is necessary to document these works by signing the Act of breakdown of temporary passage on the ground in accordance with the form given in Appendix 2, RD-11-02-2006.
3.4.4. Before the start of each type of work, the boundaries of potentially dangerous zones should be established at a distance of 5 m. production factors, which include the movement zones of machines (loader, roller, jib crane), their parts, working bodies, as well as places over which goods (reinforced concrete slabs) are moved by a jib crane. At the boundaries of the zones, safety protective and signal fences, warning notices and safety signs should be clearly visible at any time of the day.
Fig.13. Warning signs
Fig.14. The design of the signal fence
3.4.4. In the composition of sequentially executed earthworks for cutting the vegetative layer of the soil, the following technological operations are included:
cut plant soil bulldozer with movement in shafts;
Loading of plant soil with a front loader into dump trucks;
Transportation of vegetable soil to the dump by dump trucks.
The vegetation layer should be cut, as a rule, in a thawed state. In case of difficult terrain of machines, it is allowed to remove the soil in the spring when the soil thaws to the appropriate depth.
Vegetation (fertile) layer h = 0.10 m thick, 3.50 m wide is removed from the right of way allocated for the construction of a temporary passage and placed in shafts, which are located on the passage.
Working according to the "shuttle scheme", the vegetable soil is removed and moved bulldozer DZ-42 across the entire right-of-way.
When cutting vegetable soil according to the "shuttle scheme", filling the dump with soil, its movement is carried out when the bulldozer moves forward, and idling- when the bulldozer is reversing along the same straight line.
In this case, each cycle of cutting and moving the soil is carried out with the overlap of the previous track by 25-30 cm with the movement of the cut soil into a cone for its further loading into dump trucks and removal to designated places.
Each cycle of the bulldozer for cutting the vegetable soil is carried out in the following technological sequence:
Lowering the blade and setting it to the required position;
Cutting and filling the dump with soil;
Moving the soil of the vegetative layer to the place of laying;
Unloading (laying) the soil of the vegetative layer into the dump;
Moving the bulldozer into the face to the next grip.
When removing and storing the fertile soil layer, measures must be taken to prevent the deterioration of its quality (mixing with underlying mineral layers, underlying non-vegetative soil, pollution with waste, construction waste, erosion, blowing, freezing, etc.).
The soil of the vegetative layer is loaded from the dump wheel loader Volvo L45В
in dump trucks KAMAZ-6520
.
Soil is loaded by a loader from the side of the dump truck. The soil is removed to the places determined by the POS, where it is unloaded into a dump for delivery to the land user.
The performed work on cutting the vegetation layer of the soil must be presented to the representative of the Customer's building control for technical inspection. In the absence of defects, as well as after the elimination of deficiencies, it is necessary to document these works by signing the Inspection Certificate hidden works, in accordance with Appendix 3, RD-11-02-2006 and obtain permission to carry out subsequent work on the preparation of the natural base.
3.4.5. The preparation of the soil base for the embankment of the subgrade consists in its alignment, planning and compaction.
Alignment of the surface of the base under the embankment is carried out bulldozer DZ-42 by cutting bumps, backfilling holes, ruts and irregularities (more than ±0.1 m), longitudinal passes in two passes along the track, overlapping the previous pass by 0.5 m.
Alignment of the surface of the base under the embankment is carried out in strips equal to the width of the bulldozer blade, with a working stroke in one direction (see Fig. 15).
Fig.15. Scheme of laying out a natural base by a bulldozer
The surface of the soil base should be planned for a gable transverse profile with a slope of 40‰ to the crests of the passage and ensure the rapid removal of precipitation.
In view of the fact that the soil at the surface zone (5-10 cm) of the natural soil base obtained from cutting the vegetation layer, as a rule, has a slightly lower value than required, due to its horizontal shift by the roller during compaction ("bulldozer effect "), it is necessary, when preparing for the construction of the subgrade, to compact this zone with the help of a road, self-propelled, soil vibratory roller DU-85 for 3 passes along one track, by shuttle passes at a working speed of 6.0 km/h, with the vibrator turned off, starting from the edge of the base, with each pass moving towards the axis by 2/3 of the compacted strip, with each previous pass overlapping by 0.3 m, up to compaction factor 0,98 .
Completed work on the preparation of the natural base must be presented to the representative of the Customer's building control for technical inspection. In the absence of defects, and also after the elimination of deficiencies, it is necessary to document these works by signing the Concealed Works Examination Certificate, in accordance with the form of Appendix N 3, RD-11-02-2006, and obtain permission to perform subsequent work on the installation of a sandy underlying layer.
3.4.6. To ensure the scope of work on the arrangement of the sandy underlying layer, work on the arrangement of the trough must be carried out ahead of at least one shift.
3.4.7. The completion of the preparatory work is recorded in the General Journal of Works (The recommended form is given in RD 11-05-2007).
3.5. The device of the sandy underlying layer
3.5.1. Underlayment created for:
Elimination of irregularities of the natural base;
Ensuring the movement of coating slabs when the ambient temperature changes;
Evenly distribute pressure from cars;
Reduction of stress in the plates;
Increasing the resistance of the surface of the natural base during the construction and operation of the road.
The underlying layer performs the functions of draining, frost protection, leveling and anti-silting.
3.5.2. The construction of the sub-base includes the following work steps:
Transportation of sand by dump trucks;
Leveling the sand with a bulldozer;
Leveling the underlying layer with a bulldozer;
Compaction of the layer with soil rollers;
Watering with water when the moisture content of the sand is less than optimal.
3.5.3. Before starting work on the installation of the underlying layer in winter, the natural base must be cleared of snow and ice in the area of the replaceable grip. In snowfall and blizzard, work on the device of the layer should be stopped.
3.5.4. Sand for the underlying layer is mined in a quarry excavator Volvo EC-290B and delivered to the place of work dump trucks KAMAZ-6520.
Sand is delivered to the prepared base of the trough based on the required layer thickness. The value of the required thickness, taking into account the sand safety factor for compaction equal to 1.10, is found by the formula.
, m,
Design layer thickness, m
Required compaction factor, Table 22, SNiP 2.06.02-85
Coefficient of initial compaction: bulldozer 0.800.85
Sand layer settlement value, 3%
The imported sand is unloaded from dump trucks onto the surface of the base of the trough in heaps. The distance between the centers of unloaded heaps of soil is determined by the formula:
Where is the carrying capacity of a dump truck, tons.
Heap leveling strip width, m
Thickness of the technological layer of backfill, m
Sand compaction safety factor=1.10.
Volumetric weight of sand, t/m.
Maintaining the required distance will not only guarantee desired thickness of the underlying layer and ensuring the quality of its compaction, but will also minimize the work of the bulldozer and motor grader on leveling heaps and save time and fuel and lubricants. Sand is received at the unloading site by a road worker, who gives a signal for the approach and departure of the car, stops at the designated places for unloading materials.
3.5.5. Sand leveling in the layer is performed bulldozer DZ-42 in four passes, with the movement of soil from the heap to a distance of up to 3.0 m in layers = 0.11 m thick, according to the shuttle scheme from the edges to the middle for the entire width of the trough, with overlapping of the previous track by 0.4-0.6 m at operating speed in second gear in the "away from you" way (see Fig. 16)
Fig.16. Scheme of work on the construction of the sandy underlying layer:
1 - distributed sand; 2 - leveling sand with a bulldozer; 3, 4 - delivered sand
3.5.6. For profiling the upper part of the underlying layer, it is carefully planned according to design marks. bulldozer DZ-42 according to the shuttle scheme for two passes along the trail, in 1st gear. Planning should begin with the lowest (in the longitudinal plan) sections. First, they cut off the bumps, the existing "comb", and fill in the holes, and then proceed to the general layout along the entire length of the grip. The overlap of traces during layer planning should be 0.5 m. In the process of profiling, to ensure the evenness of the layer, it is necessary to remove or add sand. The surface of the backfilled layer should be planned for a gable cross profile with a slope of 40‰ to the crests of the driveway and ensure rapid removal of precipitation.
3.5.7. To achieve the required density of the underlying layer =0,98 sand during compaction should have an optimal moisture content of 8-12% or differ from the optimal one by no more than 0.90-1.05.
in dry and hot weather to bring sand to optimal humidity and ensuring its better compaction 20-30 minutes before compaction, the surface of the layer is poured with water using watering machine PM-3U
.
The required amount of water to moisten 1.0 m of the laid layer is determined by the formula
