I. Selection of technical scheme for artificially lowering groundwater level
For areas with rich groundwater and complex soil, the selection of dewatering methods directly affects the quality of waterproof construction and the safety of foundation pit and surrounding environment to a certain extent, so the selection of dewatering methods must be cautious. Appropriate dewatering methods should be selected according to engineering geological conditions, surrounding environment of foundation pit, supporting structure form and dewatering depth. The following are several precipitation methods for reference.
Second, the concrete structure self-waterproof construction technical requirements
1. The impermeability grade of waterproof concrete shall not be lower than P6.
2. Waterproof concrete shall be continuously poured in layers, and the thickness of layers shall not be greater than 500mm. Avoid leakage vibration, under vibration and over vibration.
3. Waterproof concrete should be poured continuously with few construction joints. When leaving construction joints, the following requirements shall be met:
1) The horizontal construction joint should not be left at the place where the shear force is maximum or at the junction between the bottom plate and the side wall, but should be left on the wall not less than 300mm above the bottom plate surface. The horizontal construction joint combined with the arch (slab) wall should be left below the arch (slab) wall joint 150 ~ 300mm. When there are reserved holes in the wall, the distance between the construction joint and the hole edge should not be less than 300 mm.
2) The vertical construction joints should avoid areas with more groundwater and fissure water, and should be combined with deformation joints.
4. The construction of construction joints shall meet the following requirements:
1) Before pouring concrete for horizontal construction joints, the surface laitance and sundries shall be removed, then clean cement slurry or concrete interface treatment agent, cement-based permeable crystalline waterproof coating and other materials shall be laid, and then 30 ~ 50m thick 1: 1 cement mortar shall be laid. And should be timely pouring concrete.
2) Before pouring concrete for vertical construction joints, the surface shall be cleaned, and then the concrete interface treatment agent or cement-based permeable crystalline waterproof coating shall be painted, and the concrete shall be poured in time.
5. Waterproof concrete shall be cured by heat preservation and moisture preservation before final setting, and the curing time shall not be less than 14d.
Three, the basement waterproof coiled material and waterproof coating construction technical requirements
1, coiled material waterproof layer construction
1) The coiled material of the concrete part of the structural floor cushion can be constructed by empty laying method or point bonding method, and the coiled material of the side wall part and the coiled material of the roof part should be constructed by full bonding method. When laying the waterproof layer of the facade coil, measures should be taken to prevent the coil from falling off.
2) When laying double-layer coiled material, the seams of upper and lower layers and adjacent two layers of coiled material should be staggered by 1/3 ~ 1/2 width, and two layers of coiled material shall not be laid vertically.
3) When laying the external waterproofing membrane, the following requirements shall be met: first lay the plane, then lay the facade, and the junction shall be overlapped.
4) When the waterproof layer of coiled material is laid by the method of external defense and internal sticking, the following requirements shall be met: the coiled material shall be paved with elevation first, and then with plane; When the facade is paved, the corner should be paved first, and then the bedding face should be paved.
2, coating waterproof layer construction
1) Before coating construction. At the grass-roots level, the angle of Yin and Yang should be arc-shaped, the diameter of the angle of Yin should be greater than 50mm, and the diameter of the angle of Yang should be greater than10 mm..
2) Waterproof coating should be painted or sprayed by layers, and the painting should be uniform, and it is not allowed to be painted or painted. Brushing should be carried out after the previous layer of paint is dried and formed into a film, and the brushing direction changes alternately every time, and the width of the same layer of paint is 30 ~ 50 mm in turn.
3) In corners, deformation joints, construction joints, through-wall pipes and other parts, matrix reinforcing materials and waterproof coatings should be added, and the width should not be less than 50 mm ... The lap width of matrix reinforcement should not be less than100 mm.
Four, underground waterproof engineering construction quality problems.
1 leakage of waterproof concrete construction joints
cause analysis
1) Improper position of construction joint.
2) In the process of formwork support and steel binding, sundries falling into the joint are not removed in time. After the last concrete pouring, an interlayer was formed between the old and new concrete.
3) When pouring the upper concrete, the construction joints are not treated as required, and the upper and lower concrete cannot be firmly bonded.
4) The steel bars are too dense, the spacing between internal and external formwork is narrow, the concrete pouring is difficult, and the construction quality is not easy to guarantee.
processing method
1) According to the leakage situation and water pressure, accelerate coagulation slurry or cyanation grouting is used to stop the leakage.
2) Non-leakage construction joints can be chiseled into splayed grooves along the joints, the loose stones will be cleaned, the base will be made with cement slurry, and leveled and compacted with 1:2.5 cement mortar.
2) Non-leakage construction joints can be chiseled into splayed grooves along the joints, and loose stones can be hoisted out and scrubbed clean.
2, waterproof concrete crack leakage
cause analysis
1) concrete is mixed unevenly, or cement varieties are mixed, resulting in cracks due to different shrinkage.
2) The lateral pressure and water pressure of soil are not well considered in the design, and the structure lacks sufficient stiffness.
3) Local fracture or annular crack occurs due to design or construction reasons.
processing method
1) use accelerating slurry or cyanation grouting to stop the leakage.
2) For non-leakage cracks, mortar or cement grouting method can be adopted.
3) For the annular cracks in the structure, buried rubber waterstops, buried waterstops and bonded neoprene sheets can be used.
3. Coil drum
cause analysis
There is moisture and gas in the parts where the waterproof layer of the coiled material is not firmly bonded; When affected by solar radiation or artificial heat source, the volume expands and bubbles are produced.
processing method
1) Small and medium-sized bubbles with a diameter less than 100mm can be treated by glue extraction and glue filling, and a few bricks can be pressed, and the bricks can be removed in a few days.
2) For bubbles with a diameter of 100 ~ 300 mm, the protective layer at the bubble can be removed first, and then the bubble can be cut into an oblique cross shape with a knife to release the gas in the bubble, dry the water, remove the old cementing material, and blow dry the coil with a blowtorch. Then re-glue the old coil pieces in sequence, and then glue a new square coil (the side length of which is larger than the operation range 100mm) and press it into the coil; Finally, paste the covering coil, lap it on four sides, and re-do the protective layer.
3) Cutting and repairing the bubbles with larger diameter. First, cut off the bubbling coil with a knife, clean up the base according to the previous practice, and then bake the old coil with a blowtorch. After removing the old cement, paste the old coil in turn, spread a new coil (the overlap with the old coil is not less than 100mm), and then paste the old coil. Then paste the old coil in turn, then cover the second layer of new coil, and finally paste the coil, compact and scrape off the periphery, and redo the protective layer.
The above are collected and sorted by Zhong Da Consulting Company.
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