With the development of society, urban construction attaches more and more importance to urban soil and water conservation and environmental protection, because permeable bricks have excellent water permeability and ventilation functions, can absorb moisture and heat, regulate the temperature and humidity of some surface spaces, and reduce the pressure of urban drainage and flood control Therefore, permeable bricks will be used more and more widely in urban construction.
1 the effect of permeable bricks in the laying of municipal roads
There are three effects of laying permeable bricks in the city. The top of the list is to prevent water in road areas and repair groundwater. Rainwater is an important water resource, and permeable bricks can quickly absorb standing water. After the brick body is soaked, water moves in the open space between the bricks, and laying a permeable brick pavement in the city can reduce municipal drainage capacity and prevent road area water during heavy rainfall. On the other hand, rainwater infiltrates the soil through permeable bricks , increases soil water storage, circulates water resources naturally, and improves ground settlement. Second, it can reduce the urban heat island effect. Compared with hardened roads, permeable bricks can absorb heat and adjust the temperature and humidity of some parts of the ground surface, which is equivalent to changing the thermal properties of the underlying surface. The heat absorption is slow and the heat capacity is large. Under the same solar radiation conditions, the temperature rises slowly. The exterior temperature is significantly lower than the hardened pavement. Because of its good water retention and large amount of heat dissipated by evaporation, it has a greater effect on mitigating the urban heat island effect. Third, permeable bricks deepen the underground water and steam the declared moisture, which can increase humidity, improve climate, and reduce respirable dust and particulate matter.
2 Application of permeable bricks in the practice of municipal engineering
In a municipal project in Linyi, the pavement is 9m wide with 3m sidewalks and 3m green belts on each side. The pavement uses a two-way cross slope of 2%, a sidewalk cross slope of 2%, and a green belt cross slope of 3%. Drawing planning requirements: the bottom layer is compacted soil foundation, the compaction degree is controlled above 95%; the upper layer is laid with 20cm thick graded crushed stone, and the compaction degree is controlled above 96%; the upper layer is covered with 2cm thick grit Leveling layer; the surface layer is a 25cm × 25cm × 6cm thick permeable brick with a compressive strength of 30mpa. The joint is filled with 1: 2.5 (volume ratio) cement mortar.
3 Preparation for construction of permeable bricks
According to the conditions of the construction site, do a good plan for the layout, draw water and electricity into place for construction, and do temporary drainage.
Original data preparation: Select sand-free fine stone concrete compacted bricks, the surface layer is the combination of cement and quartz sand, the permeability of permeable bricks is 1mm / s, the processing of permeable bricks is machine-pressed, and the production process is relatively simple; the paving materials are mainly Conventional medium coarse sand and graded stone. Sampling and testing of the permeable bricks and sand and gravels on the scene, and the products can be used only after the quality is qualified.
When the permeable bricks are stacked, they should be handled with care, organized and stacked separately in batches, colors, and categories. Plates with cracks, corners, warpage and appearance defects should be removed. Permeable bricks of different types must not be used in a turbid manner.
According to the construction organization plan and plan, organize machinery and equipment and workers to go out for construction.
In particular, how to ensure the horizontal and vertical joints of the permeable bricks are consistent with the horizontal and vertical joints of the curbstones on both sides of the highway. The vertical elevation and flatness are coordinated with the highway. The measurement and control is the main point of this project. For this purpose, two j2 theodolites and one ds3-1 level are equipped.
4 Pervious brick laying construction technology
4.1 Construction control measurement
In order to ensure that the plane orientation and elevation of the pavement meet the requirements of the drawing plan and reach excellent standards, the plane control is implemented in three levels. The first level of the list is the highway control point, which is used as the measurement control basis for this standard section. The second level is to determine the sidewalk orientation of the sidewalk, and to control the pile position along the sideline. The third level determines the pavement area to control the grid. Demand for paving permeable bricks . During field measurement, the elevation is marked on the φ10 steel bar, and the nylon rope with better elasticity is used as the basis for the elevation control of the pavement construction.
4.2 Site leveling
Because the sidewalk foundation is backfilled earth subgrade, it is backfilled synchronously with highway subgrade, layered and rolled to ensure that the compactness of each layer meets the planning requirements, and the compaction degree of the road bed is ≥95%. According to the calculation results, level the piles manually according to the leveling line. After leveling, use a 2.5t small roller to level it again.
4.3 Paving curb
Construction stakeout-sorting out the underlayer-device. (1) After the construction is set up and the ground floor is paved and photographed, the curb stone construction is set out, and the curb stone device control points are released according to the kilometer center line (one point every 10 meters). (2) After staking out, sort out the surface of the lower layer, and remove debris, sand, soil and other debris from the surface to make the surface clean and tidy, and sprinkle water on it before the curb stone device. (3) Install curbstone, firstly lay a layer of mortar along the curbstone device control line to ensure the plane orientation and elevation of the curbstone are accurate; secondly, place curbstone and smooth the mortar after the mortar is smoothed. Check the curb stone to see if its side, top surface is smooth, and whether the width of the seam meets the requirements. If it is unqualified, adjust it from the beginning and then sew again. After the laying of curbstone, the quality inspection team inspected targets such as straightness, seam width, the height difference between the two adjacent blocks, and the top surface elevation. Unqualified sections were laid from the beginning.
4.4 Graded crushed stone layer construction
Measuring and laying line-laying grading gravel-rolling grading gravel. (1) Measure and stake out: According to the calculated measurement data, the surveyor marks the elevation points with paint on the curbstones on both sides, and presses the same amount to return to a certain height as the top surface of the grading gravel cushion. (2) Laying graded crushed stones: When the graded crushed stones are on the field, each batch must be inspected, and paving can only be performed after passing. In order to prevent the disturbance of the bottom layer, the graded crushed stones are transported by agricultural transport vehicles, and paved artificially, with a thickness of 3 cm. (3) Rolling graded crushed stone: 2.5t vibrating roller is used for rolling. Before rolling, 3 to 4 kg of water is poured per square meter. After rolling by the roller for 3 times, vibrating and rolling for 2 times, and then static pressure for 1 or 2 times. After survival, the compaction degree of 20cm thick graded crushed stone is ≥96%.
4.5 Permeable brick construction
Preparation for construction-measurement and staking-grit screed-trial assembly and test layout-laying of permeable bricks -fine and medium sand sweeping. (1) Preparation for construction and understanding of drawings: Based on construction drawings, understand the dimensions of various parts and the orientation of permeable bricks . Bottom finishing: clean up the debris on the ground floor. Equipment preparation: check whether the transport vehicle is operating normally and supply iron trowels, buckets, rubber hammers, etc. that are required for paving. (2) Measure and stake out: The pavement brick datum point should be set on the curb stone edge, and the vertical and horizontal hanging lines should be set according to the elevation, and paved on the hanging line. (3) When paving the sidewalk tiles, first lay a layer of 2cm coarse sand for leveling. After paving, lay it down and level it with a trowel. The thickness should be 2 to 3mm higher than the horizontal line, and then permeable bricks should be laid. (4) Trial spelling and trial rowing: Trial spelling of each permeable brick according to orientation and viewpoint before laying. In order to check the gap between bricks, check whether the orientation of the bricks is consistent with the plan drawing. Before the official paving, a trial run is required. (5) When paving permeable bricks , place the bricks on the paving orientation to the horizontal and vertical joints, and then tap the center of the plate with a rubber hammer to make the coarse sand dense and hammer to the paving height. Use a rubber mallet to tap the wooden pad placed on the board to make the board level. Use a spirit level to level the board according to the horizontal line. Check at any time during paving. If there is any open space, the permeable bricks should be lifted up with coarse sand and then be laid. (6) After the pavement is finished, organize the seam stitching. Before the seam stitching, it is necessary to hang the thread again and adjust it to be straight, smooth and flat before the seam stitching can be performed. First remove the soil and debris in the joint and clean it, and moisten it with water. Then fill the joint with 1: 2.5 (volume ratio) cement mortar to fill the joint.In summary, the application of permeable bricks in municipal road projects has a broad prospect for promoting urban soil and water conservation and environmental protection.