The room below the first floor of a building is called the basement, which uses underground space and saves construction land.
Basement is divided into ordinary basement and air defense basement according to function; According to the roof elevation, there are semi-basement (buried depth is 1/3 ~ 1/2 times of the clear height of the basement) and full basement (buried depth is greater than 1/2 times of the clear height of the basement); According to the structural materials, there are brick basement and reinforced concrete basement.
A. Composition of common basement
The basement consists of five parts: wall, bottom plate, top plate, doors and windows, and elevator.
1. The external wall of the wall basement shall be designed according to the retaining wall. If reinforced concrete or plain concrete wall is used, it should be determined by calculation. Its minimum thickness should meet the structural and impermeability requirements. Its minimum thickness is not less than 300mm, and the external wall should be moisture-proof or waterproof. For example, the thickness of brick wall (rarely used now) is not less than 490 mm ..
2. The roof can be made of precast slab, cast-in-place slab or cast-in-place layer on precast slab (assembled integral floor slab). If it is a civil air defense basement, cast-in-place slab must be used, and its thickness and concrete strength grade should be determined according to relevant regulations. On the roof of the unheated basement, that is, the first floor, an insulation layer should be set to facilitate the comfortable use of the first floor rooms.
3. When the floor is above the highest underground water level and there is no possibility of bearing pressure, it can be treated as general ground engineering, that is, the cast-in-place concrete on the cushion layer is 60~80mm thick, and then the surface layer is made; If the floor is below the highest groundwater level, the floor will not only bear the vertical load of the upper part, but also bear the buoyancy load of the groundwater. Therefore, the reinforced concrete floor should adopt double-layer reinforcement, and a waterproof layer should be set on the cushion under the floor to prevent leakage.
4. Doors and Windows The doors and windows of the ordinary basement are the same as the rooms on the ground. When the local lower outdoor window is lower than the outdoor floor, a lighting well and a protective grille should be set to facilitate indoor lighting, ventilation and outdoor walking safety. General air defense basement is not allowed to open windows. If it is necessary to open the window, strict measures should be taken in wartime. The outer door of air defense basement should be equipped with corresponding protective structure according to the requirements of air defense grade.
5. Stairs can be set in combination with rooms on the ground, and single stairs can be set in the basement with smaller floors or used as auxiliary rooms. The basement required for air defense should have at least two safety exits to the ground, and there must be an independent safety exit. There should be no tall buildings around this exit, in case of air raid collapse, blocking the exit and affecting evacuation.
Moisture-proof and waterproof structure of basement
1. The basement moistureproof and waterproof principle
According to the waterproof grade of basement, different foundation soil and groundwater level, and the possibility of water accumulation, the moisture-proof and waterproof scheme of basement is determined.
When the designed maximum underground water level is higher than the basement floor, or the soil around the basement is weakly permeable, and there is a possibility of water accumulation, waterproof measures should be taken. When the soil around the basement is highly permeable, the designed maximum underground water level is lower than the basement floor, and there is no possibility of water accumulation, moisture-proof measures should be taken.
2. The basement moistureproof
When the designed maximum groundwater level is lower than the basement floor, and there is no possibility of stagnant water in the upper floor, groundwater cannot be immersed in the basement, and the basement floor and external wall can be moisture-proof, and the basement moisture-proof is only suitable for preventing diving.
The structural requirements of basement moistureproof are: the brick wall must be built with cement mortar and the mortar joint must be full; The outer side of the outer wall is provided with a vertical moisture-proof layer. Generally, the method of moistureproof layer is: 1: 2.5 cement mortar leveling, cold priming oil once and hot asphalt twice. Outdoor aproll is used as moistureproof layer, and then low-permeability soil such as clay and lime soil is backfilled on the outside of the moistureproof layer, and compacted layer by layer, with a bottom width of about 500mm. In addition, all walls in the basement must be provided with two horizontal moisture-proof layers, one near the bottom, generally between structural layers. The other is located above the outdoor ground apron 150~200mm.
3. The basement waterproof structure
At present, there are two waterproof measures: coiled material waterproof and concrete self-waterproof.
(1) waterproofing of coiled material
There are two construction methods for waterproofing coiled materials: external waterproofing and internal waterproofing. When the coiled material waterproof layer is located on the outside of the underground engineering envelope (that is, facing the water surface), it is called external waterproofing, which has good waterproof effect; When the coiled material is stuck on the inner surface of the structure, it is called internal waterproofing. This method has poor waterproof effect, but it is simple in construction and convenient in maintenance, and is often used in maintenance projects.
External defense and external sticking method: firstly, build a permanent protective wall around the concrete cushion with cement mortar leveling layer, dry lay a layer of coiled material at the lower part as isolation layer, and build a temporary protective wall with lime mortar at the upper part, then lay a plane first, and then lay a facade, and the plane and facade should overlap. After the waterproof layer has been laid and passed the inspection, the protective layer shall be constructed immediately, and then the main structure shall be constructed. After the completion of the main structure, dismantle the temporary protective wall, and then make the waterproof layer of the external wall. The construction method is shown in Figure 2. 19. The waterproof layer of the coiled material is directly pasted on the external surface of the main body, and the waterproof layer is synchronized with the concrete structure, so it is less affected by the settlement and deformation of the structure, and it is not easy to damage the waterproof layer during construction, and it is also convenient to check the waterproof quality of the concrete structure and the coiled material, and it is easy to repair problems when found. The disadvantage is that the waterproof layer needs to be constructed many times, with many processes, long construction period, large working face, large earthwork and formwork, and the seam of the coiled material is not easy to protect, which easily affects the quality of waterproof engineering.
External defense and internal sticking method: firstly, a permanent protective wall is built on the cushion of waterproof structure, and a 1: 3 cement mortar leveling layer is painted on the inner surface of the protective wall. After basic drying, stick the waterproof layer of the facade coil on the wall. Permanent protective wall can replace external formwork, but reinforcement measures should be taken. After the protective layer is prepared on the surface of waterproof layer, the waterproof structure can be constructed. The construction method is shown in Figure 2. 19. Waterproof layer construction can be completed at one time, with simple process, short construction period, less construction land, less earthwork and less external formwork. The waterproof layer of coiled material can be continuously laid without temporary stubble fixation. Its disadvantage is that the waterproof layer of vertical wall is difficult to synchronize with the three-dimensional structure, and it is easy to be damaged due to structural settlement and deformation. It is difficult to check the quality of waterproofing membrane and structural concrete. If there is leakage, it is very difficult to repair the waterproof membrane.
(1) Self-waterproofing of reinforced concrete
The impermeability label is determined according to the ratio of the highest calculated water head to the minimum wall thickness of waterproof concrete structures.
The preparation of waterproof concrete can adopt aggregate grading method and waterproof admixture method. The aggregate grading method is to relatively weaken the stone skeleton and appropriately increase the sand ratio and cement dosage. Cement mortar can not only meet the full bonding effect, but also form a certain number of high-quality wrapping layers around the coarse aggregate to separate the coarse aggregate, thus improving the compactness and impermeability of concrete. Waterproof admixture method refers to adding a certain amount of admixture to concrete, such as air entraining agent, water reducing agent, triethanolamine, ferric chloride, alum, UEA and other expansion agents, to improve the waterproof performance of concrete itself.
In addition to the above waterproof measures, auxiliary drainage and drainage measures can effectively enhance the waterproof effect of the basement.
Dewatering and drainage methods can be divided into external drainage method and internal drainage method. The so-called drainage method means that when the water level in the basement is higher than the basement floor, permanent drainage facilities are set around the building, and blind ditch drainage is usually used, that is, perforated sleeves are buried around the building and below the elevation of the basement floor. Fill pebbles, coarse sand and other materials that can filter water around the casing, so that the groundwater can flow into the collecting well in an organized way, and then be discharged into the urban drainage pipe network by gravity or mechanical drainage, so that the groundwater level is lower than the basement floor, and the confined water becomes diving. Reduce or eliminate the influence of groundwater.
Drainage method is to drain the water seeping into the basement to a low-lying place or mechanically through a permanent gravity drainage system. However, the latter should fully consider the impact of water level rise caused by power outage. Structurally, the basement floor is often overhead, or a water-resisting layer is set to keep the indoor wall and floor dry, and then discharged to the water storage well through the collecting well, and then pumped away by the water pump. For insurance, some important basements have both external waterproofing and internal drainage facilities.
B. Matters needing attention in the construction of air defense basement
The construction of air defense basement shall be carried out in accordance with relevant design and construction specifications such as civil air defence basement Design Code (2003 edition), Civil Air Defense Engineering Construction and Acceptance Code (GB50 134-2004), Civil Air Defense Engineering Quality Inspection and Evaluation Standard and Underground Waterproofing Engineering Quality Acceptance Code (GB50208-2002). Combined with the construction site inspection, the specific problems encountered in the actual construction are as follows:
Construction drawings must be approved by the municipal civil air defense office or the design review agency entrusted by it before construction.
First, floor pouring
1. According to the bottom plate load, it mainly bears loads such as water pressure and equivalent static load of civil air defense from bottom to top, and the upper reinforcement of the bottom plate generally passes under the upper main reinforcement of the bottom plate beam.
2. Setting of sealing groove. According to the General Staff Atlas, external entrances and exits are blocked by 500× 150 groove (HFL series) or 300× 150 groove (GLF series); The communication port between FMDB series protection units is sealed with a frame sealing groove of 140× 130, and the elevation of the bottom frame should be flush with the building elevation. When the concrete thickness of the surface layer of the floor post-pouring belt is less than 150, the floor structure must be treated with local groove structure, such as lowering the floor locally in the form of gutter and strengthening it with steel bars; If it is greater than 150, a groove can be set on the back pouring surface. The corner of the groove should be strengthened by angle steel welded with anchor hook.
3. Before pouring the basement floor, the embedded bottom frame (HFL series or GLF series) is used for external entrances and exits; Interpolation (FMDB series) must be manufactured and installed as a whole and cannot be separated. When the thickness of the screed-coat after pouring concrete on the bottom plate is greater than 150, it can be installed together with the protective door frame before pouring the side wall.
4. Frame reinforcement shall be set at the bottom of the threshold. In immovable civil air defense doors, the building elevation of reinforced concrete civil air defense threshold is generally 150 (the lowest can be 120), and the steel door varies from 30 to 200 according to the specific model. The movable threshold requires the thickness of the leveling layer on the ground to be greater than 100, so that the angle steel of the door frame bottom frame L 100 can be buried. When the thickness is less than 100, the cushion layer should be raised locally. Considering the design resistance, except that the elevation of reinforcement is higher than the bottom frame threshold 150, U-shaped vertical reinforcement should be set under the bottom frame as the bottom frame threshold. At this time, two 1000 long 16 steel bars should be embedded in each corner of the door and valve frame wall.
5, explosion-proof floor drain, call ammonium button and sewer pipe embedded. If the cushion of the post-pouring belt of the basement floor is below 150, it is suggested that the construction unit connect the explosion-proof floor drain with φ 80 steel pipe and embed it to the design elevation before pouring the floor concrete. In addition, wartime water tanks, wartime dry toilet floor drains and drainage pipes should not be buried.
6. Several protection units are connected. If there is only one explosion-proof cable well, the wartime power supply connection between cross protection units must be connected with galvanized steel pipes in the bottom plate for threading (cables), and cable threading pits should be set at the bottom plates on both sides of the partition wall of the protection units.
Second, the side wall pouring
1, the width requirement of the portal stack. According to Article 3.4. 1 1 of Code for Design of Air Defense Basements (2003 edition), when the width of the protective door opening is less than or equal to 1000, the widths of the two cribs should be greater than 350 and150 respectively; If the width of the protective doorway is greater than or equal to 1200, the two cribs must protrude more than 400 and 200 respectively. According to the atlas of the General Staff Department, the number of doorframes blocked and protruding before the war should be more than 300. Considering the structural resistance and the masonry space of the internal brick wall, the thickness of doorframe wall should be more than 500. The side of the blocking side should be flush and the side of the inner side should be flush. In addition, the wall thickness of two doors in a frame should be above 500.
2. The horizontal reinforcement of the door frame wall of the protective door is a stressed steel bar, which should be arranged on the outside. Unlike the horizontal reinforcement of other walls is an internal auxiliary reinforcement, the stressed steel bar of the door frame wall should be closed.
3, door frame template inspection. According to Article 6. 1.9 of the Standard for Quality Inspection and Evaluation of Civil Air Defense Engineering (RFJ0 1-2002), the allowable deviation of the door frame wall is 2.5‰, that is, the vertical deviation of the door frame wall is generally 2 meters high, which should be controlled within 5 mm Civil air defense door manufacturers have generally adjusted the door frame vertically and horizontally when installing the door frame, and formwork support may cause the door frame deviation. Supervision units shall, in accordance with the standards for civil air defense quality inspection and evaluation, inspect the civil air defense equipment entering the site, and put an end to unqualified products.
4. When installing reinforced concrete civil air defense wall formwork and concrete beam formwork at the separation point of the protection unit, wall bolts with sleeves shall not be used, and disposable bolts with water stop wing rings shall be used to avoid causing holes in the walls and beams.
5, ventilation, water supply and drainage, electrical related embedded casing can't leak buried, each major should review in time, generally highlight the wall, specific methods can be found in the detailed drawings of each major; When the pipeline of equipment, electricity, etc. When crossing the external wall and the protective sealing wall/mouth sealing wall, a fixed sealing plate should be added. See the drawings and reference atlas for the reserved embedment of wind protection and water and electricity.
6, civil air defense door frame Angle reinforcement should be 50 apart from each other. The civil air defense door is selected according to the General Staff Atlas, and two lock boxes (attached to the angle steel side of the door frame) are respectively arranged on both sides of the civil air defense door. In order to prevent the vertical steel bars at the corner of the door frame from colliding, the steel bars should be pulled away from the door frame 50 when binding the steel bars, so as to prevent the steel bars from being cut off after the civil air defense door is installed, or even if it is squeezed in, it is easy to cause the door frame and the wall steel mesh to shift and tilt together.
7, civil air defense door embedded frame should be fixed firmly. In order to ensure the correct installation of the civil air defense door and prevent the dislocation and pouring deformation of the nail template, steel pipes or angle steels are generally used as temporary supports to fix and reinforce the civil air defense door and the sealing frame, and cannot be knocked off at will during construction. If it is really necessary for temporary demolition due to construction traffic, it must be welded back before concrete pouring, and adjusted horizontally and vertically, otherwise it will easily cause the door frame to tilt or deform, which will affect the normal opening of the protective door.
8, play the wall and give the relevant civil air defense door threshold elevation. After the pouring of the bottom plate is completed, before the installation of the civil air defense door, the formwork worker pops up the edge line of the door frame wall in time, and according to the requirements of slope finding, the building elevation of each door sill is given horizontally, which is convenient for the installation and frame sealing positioning of the civil air defense door. At this time, it must be noted that if the basement wall is brushed with mortar for leveling during decoration, the formwork must be recessed into the angle steel surface of the civil air defense door frame with a certain thickness when shuttering; If the basement wall is decorated with white paint, the template can be attached to the door frame. At this time, the flatness of the formwork and the quality of concrete pouring are required to be higher.
9, threshold concrete can't leak pouring. When pouring the side wall, the concrete under the civil air defense door and the threshold of the emergency stop frame must be poured together, otherwise it is easy to bend and deform the angle steel of the door frame due to carrying things when leaving the door frame blank, and the concrete under the emergency stop frame with cushion must be poured first.
10 and * * install fire doors on the door frame wall. If the design is limited by space, fire doors and protective sealing doors should be installed on the wall of civil air defense door frames. At this time, it should be noted that the civil air defense door is equipped with a locking device, which protrudes about 100. In order to ensure the normal opening of the civil air defense door and facilitate the opening of the fire door, the fire door should be installed along the inner side of the corner of the door frame, so as to be both protective and fireproof.
1 1. The explosion-proof call ammonium button on the opening side of the air-tight door of the air outlet shall be embedded in place before pouring the side wall.
12, the anchorage length of reinforcement must meet the requirements. According to Article 3.6.4 of National Technical Measures for Civil Building Engineering Design-Air Defense Basement, the anchorage length of tensile reinforcement in explosion-proof structure is laB= 1.05la, and the lap length of longitudinal tensile reinforcement is llB= 1.05ξ 1la.
13. The door frame wall, airport wall and reservoir retaining wall that protect the sealed door and sealed door must be built as a whole without horizontal construction joints.
14, please be careful not to miss the construction of explosion-proof cable shaft on the side wall.
Third, the roof casting
1, the roof hook is embedded. Facing the war, civil defense doors blocked on the roof and civil construction units with embedded hooks cannot be buried. There are three main hook positions: the protective door is buried in the side door opening, 200 reinforced concrete doors (including 400 movable civil air defense doors) and 400 steel doors; The external seal of the external inlet and outlet is located at the center of the inner side of the sealing frame 300 away from the edge of the door opening; The internal plug between the protection units is set at the center of each meter on the plug side, which is 100 away from the edge of the door opening.
2. Inlet roof overpressure pressure measuring device DN 15 galvanized steel pipe is embedded.
Fourth, the intermediate structure acceptance
Requirements: bottom plate, side wall and top plate are dry without leakage; The installation of the door frame of the civil air defense door meets the requirements of accuracy, and there is no big deviation; All embedded sleeves, pipes, ironware, hooks, etc. Construction in place, no leakage;
Five, paint and equipment installation and debugging
Equipment should be installed in place according to the construction drawing design, and there is a debugging report.
Six, civil air defense special acceptance
According to the special acceptance criteria for civil air defense, the construction unit shall, jointly with the construction unit, sort out the construction technical data related to the acceptance, do a good job in the conversion scheme of peacetime and wartime functions, fill out the application form for special acceptance of civil air defense projects, and report it to the civil air defense special acceptance office of our bureau before the general acceptance. Our bureau will carry out special acceptance of civil air defense within 5 working days, and issue preliminary acceptance opinions on special acceptance of civil air defense. After the relevant problems are rectified and qualified, the relevant personnel's special acceptance materials shall be submitted in full, and the approval opinions for the special acceptance of civil air defense shall be issued.