Hengshui Kaixiang explains the outline of underground engineering subway construction waterstop project

Subway stations constructed with grading and large-scale excavation methods: The general waterstop method is basically: double-sided (or single-sided) self-adhesive waterstops are used for the structural floor and side walls. The waterstops (must be attached) are used for the side walls and top plates. Component polyurethane waterstop coating This type of subway waterstop construction is easy to achieve a more satisfactory waterstop effect. In terms of waterstop construction management and specific quality control, this type of complete waterstop project is roughly as follows: ), start Excavation and slope protection: Generally, the depth of soil excavation is about 1 meter and is not too deep. Generally, foundation treatment, reinforcement, slope protection and grading are carried out in order to improve the bearing capacity of the foundation and slope protection design. In some cases, it may be affected by land acquisition and other factors. Make it grading restricted. It is more or less possible to be affected by some adverse effects of underground confined water and the surrounding environment, such as the surrounding drainage system. Appropriate drainage, precipitation, soil dynamic monitoring and reinforcement must be used to ensure the stability of the construction site. Some good soil layers (or improvements) during excavation can be used as good backfill water-blocking layers. The order of backfill soil must be well organized and the backfill soil reserved for excavation should be properly preserved to prevent the inclusion of bad miscellaneous soil and maintain good soil mass. Properly improve the soil layer in its natural state to maintain the moisture content of the soil layer of the backfill water-proof layer at the optimal moisture content, compact it in layers (∽), and ensure that the soil compaction coefficient d is not less than. And ensure that the thickness of the water-proof backfill soil layer is not less than Less than. Basically, it can make up for the construction defects of the waterstop project and the structure itself.
), orderly and well-organized construction means to strictly organize various constructions according to the construction organization design requirements to ensure that each process has a reasonable construction period. How to determine and ensure a reasonable construction period is difficult to achieve in actual construction. Various reasons lead to overlapping, occupation, delays in the construction of related processes, or shortage or delay due to unexpected circumstances
). For each construction unit and supervisor, the process requirements for the waterstop construction to be carried out are very important. Have a complete waterstop construction plan and waterstop construction organization design and conduct strict training: at least have a complete concept and clear instructions for the acceptance and inspection standards of waterstop materials and construction processes, and also have a clear understanding of the waterstop construction. There are strict regulations on the environment and mutual cooperation required by the process, and the written handover between the processes is carried out by the relevant personnel and the supervisor's signature
). It is particularly important to fully protect the rubber waterstop in subsequent processes, especially in During and after concrete pouring, timely inspection, damage and tear prevention, repair, maintenance and anti-aging treatment are required to ensure the integrity of the waterstop project. There must be a complete written record and signature certification from the supervisor.
). For the excavation and grading construction method, the quality and working conditions of each process are much better than other construction methods. At the same time, the characteristics of water leakage in common underground projects can be strengthened purposefully here. The main tasks are:
The key to the quality of the waterstop of underground structures lies in the construction quality of the concrete. Reasonably select the concrete mix ratio to meet the needs of the waterstop concrete. Mix high-quality fly ash and high-efficiency water-reducing admixture into the concrete to reduce the cement dosage and the water-cement ratio. This can reduce the heat of hydration and reduce the probability of initial cracking of the concrete. Before concrete construction, special clarifications were made to the vibrators and reward and punishment measures were formulated to enhance the sense of responsibility of the vibrators. Layered and segmented pouring was used for the pouring of the concrete structure to ensure the tightness of the concrete pouring. After the concrete pouring is completed, a special maintenance ledger shall be established to take measures such as covering or water storage to control the temperature difference between the inside and outside of the concrete to not exceed ℃ and the curing time shall not be less than 3 days.
, Carefully handle the relevant concrete construction joints). In addition to chisel cleaning before pouring, the concrete interface agent should also be applied to the connection processing of the construction joints so that it can effectively combine with the subsequent concrete pouring.
), to deal with deformation joints, in addition to installing water-swelling rubber waterstops according to specifications, the exposed parts are also poured with polyurethane sealant and double-layer waterstops to strengthen treatment, and an hourly water storage test is conducted to prevent leakage. Concrete pouring at the waterstop: The center-mounted waterstops on the top and bottom plates should be tilted upward according to the design requirements ~ to facilitate the pouring of concrete. In case of special circumstances where the dense concrete cannot be completely vibrated, grouting should be added. Before sealing pipes or partial openings with waterstops, side walls, and roofs, the defects in the concrete surface layer should be strictly and carefully inspected, records should be kept, and the repairs should be made with the signature of the relevant person in charge and the supervisor for acceptance. .
D. Treatment of Yin and Yang Angle: The method of Yin and Yang Angle (the side wall waterstop here is a single-component polyurethane waterstop paint. Thick). According to the specification, the flange part of the bottom plate waterstop is pasted on the side wall. The side wall polyurethane waterstop is then covered and sealed with a coating film. This may cause quality hazards in actual construction. (The waterstop is too thick and cannot be effectively adhered to the side wall in a straight line.) The polyurethane coating can be applied to the bottom at one time and a double layer of paint film can be applied on the bottom to reinforce it, and then the viscosity of the paint can be used to cut the waterstop of the corresponding width. The tape is bonded to the side wall paint film layer and the swinging part of the floor waterstop. But remember that the sealing of the upper end of the swinging part of the floor waterstop is the most critical here. The upper end of the additional layer of waterstop should be covered with waterstop paint to show the shape of the water to prevent the paint from being too thick and easy to peel off.
For the roof structure, perform a water storage test before constructing the waterstop. The surface protrusions and bubble holes on the base layer of the structure must be processed before the construction of the coated waterstop. The waterstop layer should be constructed in layers and submitted for inspection. . The tie rods used to reinforce the formwork (only the grading excavation method can use tie rods to fix the formwork) are replaced by the old-fashioned single external screw rod with a three-section detachable screw rod, and a water stop ring is installed in the middle and at both ends to be removed. It not only avoids cutting damage to the structural entity, but also effectively prevents water seepage in tie rod holes and tie rod corrosion.
, a subway station constructed by excavation with concrete ground walls as the enclosure structure and steel pipes or reinforced concrete beams as the support of the enclosure structure). Compared with the subway station constructed by the grading and large-scale excavation method, it is The construction of the waterstop is more difficult. The first thing to face is the construction of the ground connection wall to ensure that the ground connection wall is basically smooth and has no major unevenness and is basically impervious to water. The key lies in the geological conditions and construction experience. The height of the ground connection wall in Wuhan Metro is generally ~ meters. The floor of the left and right subway stations is located at a depth of about 10 meters underground. The width of the station is generally about 10 meters. The ground connecting walls are faced with collapse, sand gushing, silt, methane, and underground obstacles from surrounding buildings: the basement foundation of adjacent buildings and the unknown reserves reserved during construction. Obstacles, box culverts, pipelines, etc. are generally between ~ meters underground. The underground confined water is located about ~ meters underground, and the impact of upper layer diving is generally ~ meters. Generally, overall precipitation is used to ensure the normal construction of station excavation for the sake of safety. Within the depth range of the floor, cement mixing piles are generally used for reinforcement. Relatively speaking, if the foundation is not handled properly, it will easily cause underground water and sand to surge, which will have an impact on the surrounding areas. Generally speaking, connecting walls in various places basically achieve water blocking, water isolation, and prevention of large water leakage. But as the first line of defense of underground stations and the waterstop and waterstop base surface, it has some shortcomings that need to be addressed.
), waterstop base surface treatment. Judging from some floor-to-ceiling walls that have been completed so far, the unevenness on the back surface, steel bars, and sharp objects require a lot of time to repair. At the same time, there are The supporting parts cannot be leveled and repaired in one go. The laying of waterstops leaves hidden dangers of water seepage. Currently, some construction units are not completely satisfied with the base surface of the waterstops. This is a long-standing problem for waterstops. The process of water belt base surface treatment is a tedious, meticulous, technical and patient construction process: first, various exposed iron parts are removed and rust-proofed. The anti-rust here requires that the iron parts be polymerized Secondly, repair the defects in the ground-to-ground wall: where there is water seepage, grouting should be used to repair uneven areas, smoothen the uneven areas and fill them with polymer mortar, and then use polymer mortar to find out the defects. Smooth everywhere to meet the relevant smoothness and smoothness requirements stipulated in the specification, and the waterstop will not be torn off when laying the waterstop. There are two main reasons. One is that it is labor-consuming and time-consuming and difficult to fully satisfy. The other is that the next process is made of The waterstop construction team expects them to be able to complete the construction. Therefore: the waterstop base surface treatment is the second key to the waterstop construction. There must be detailed written records and complete forms and strict handover and acceptance regulations, and should be obtained from the relevant responsible parties. and signed by the supervisor.
), the laying and protection of waterstops on the side walls of structures:
, since the laying of waterstops is the first step that crosses with tying steel bars, mold making, concrete pouring, etc. The laying is okay and there is enough working surface, but the subsequent laying and repairing are basically done on the steel bars in areas where the working surface is insufficient and the base surface of the waterstop is not well prepared (often also difficult to construct) or the Yin and Yang corners. And due to the construction progress or some other reasons, the construction of the first waterstop and the second waterstop will take a long time. The originally affixed waterstop may need to be reattached or major repairs must be made. When the steel bars have been tied, the work is more difficult and some of them are blind spots where the laying quality cannot be guaranteed.
Damage to the waterstop caused by side wall lashing steel bars and fixed formwork: Since it is impossible to use pull bolts to fix the upright formwork (it is recommended to add improved knotted tie bolts to fix one end if feasible) The other end of the formwork is fixed on the auxiliary steel bar and the pull bolt is set into a male and female type. The thread length and the adjustable length are lengthened to meet the needs of formwork adjustment. The bolts fixed on the formwork can be taken out directly) and due to the large molding area, Irregularities generally use wooden formwork (which can save time and labor, but its turnover times are limited and its rigidity is insufficient) to support the fixed formwork throughout the hall, but it is necessary to ensure that the distance between the formwork and the steel bars remains unchanged, or that the tie bars and waterstops are not watertight It is difficult to achieve this if the belts collide with each other. At the same time, due to insufficient stiffness, it is easy to run out of the formwork and leak slurry. Because of this, the vibrating strength of the construction workers is limited, and the density of the concrete cannot meet the requirements. At the same time, due to the collision between the tie bars and the waterstop, the waterstop will inevitably cause damage to the concrete. Damage to the water belt can easily cause water seepage, which is also one of the reasons why various joints are prone to water seepage during on-site inspections.
The laying of waterstops is a meticulous, time-consuming and closely related to the surrounding environment. The temperature, humidity, dust, etc. during laying are all closely related to the completed waterstops of these stations. The waterstop uses thick double-sided self-adhesive polymer modified asphalt waterstop. The waterstop (must be applied) is relatively thick and difficult to stick tightly at the inner and outer corners and concave and convex areas. Although it is fixed with cement nail pressure sheets, if the nails are fired too If the waterstop is pressed too hard without a cushioning pad, it is very easy to injure the waterstop at the joint. On the other hand, if the nailing force is insufficient or the length of the cement nail is too short or the diameter is too small, it will be difficult to fix the waterstop, so the waterstop has already been fixed. The waterstops often fall off. At the same time, each station directly lays the waterstop without applying the interface agent first (this is because the base surface of the waterstop itself is rough and uneven and it is difficult for the interface agent to work). The result is that as long as there is a waterstop If water seepage is damaged, the entire waterstop will fail and water will flow everywhere. It will be very difficult to find out where the source of water seepage is.
Protection of waterstops: The laying of waterstops is not laid completely in place at one time, but is constructed in sections, at different heights, and with various processes such as tying steel bars, molding, and concrete pouring. It is very easy to damage the waterstop. Although the waterstop is protected by a double-layer thin mold, the thin mold must be torn off at different times according to the progress of the process, and the thin mold must be retained at the reserved overlap as required. Check out some waterstops at the construction station. The film of the waterstop is not torn off prematurely, or forgets to tear it off and pour it into the concrete together. In this way, the waterstop is exposed to the air prematurely, causing it to age, become brittle, and lose its elasticity. and adhesion, or due to the thin mold that loses its water barrier and becomes a water bag, the sewage, waste residue, cigarette butts and other waste generated during the construction, as well as electric welding, etc., all give certain damage to the unprotected laid waterstop. Damage can often be seen during station inspections. The key to waterstop protection lies in management. The first is strict management system. The second is timely training at all levels to clarify the matters that everyone should pay attention to and the principles to be followed. The third is strict supervision. Repair and clean the damaged waterstop in time to prevent the hidden danger of the waterstop from entering the concrete. Fourth, when pouring concrete, be careful not to collide with the steel bars at will and strictly prohibit the vibrator from colliding with the waterstop.

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