What are the newly added construction methods in the "Technical Specification for Underground Waterproofing Engineering"?

For polymer self-adhesive membrane rolls, the construction method of "pre-paving and reverse adhesion" is advocated. They can be laid on a flat, firm, and damp base with no obvious standing water. This construction method not only accelerates the construction progress and shortens the construction period but also helps prevent the common problem of water channeling between the waterproof membrane layer and the base, which easily leads to leakage.

When laying the polyethylene polypropylene fiber composite membrane waterproof layer, it is clearly required to use the matching polymer cement bonding material, and the bonding area shall not be less than 90%.

When laying the plastic waterproof sheet layer, the construction measure of "preferably setting up a zoned pre-embedded grouting pipe system" is added, which helps avoid the problem that a single leakage point may easily affect the entire line due to water channeling.

Clear and specific regulations are made on the design and construction of the bentonite waterproof material layer to ensure the waterproof quality of this material in underground projects.

To meet the needs of fully developing and utilizing underground space, specific regulations are formulated for the design and construction of waterproofing and drainage for the planted roof of underground projects. The new specification emphasizes that a root-resistant waterproof layer must be laid on top of the ordinary waterproof layer for the planted roof.

In view of the many problems in the waterproof treatment of pile heads, the new specification clearly states that the materials used for pile head waterproofing construction should have good adhesion and wet-curing properties with the base, and should be integrated with the cushion waterproof layer. When using cement-based permeable crystalline waterproof coating, it should be applied continuously and evenly on a solid, clean, and damp base, with no under-application or missed application, and mist-like water should be sprayed in time for curing.

For the external waterproof coating of shield tunnel segments, it is advocated to use permeable and self-healing materials such as highly permeable modified epoxy coatings or cement-based permeable crystalline waterproof coatings.

The performance index requirements for concrete expansion agents used in post-cast strips shall comply with the provisions in Table 4.8.

In the cement mortar waterproof layer, the provisions in the original specification regarding "ordinary cement mortar" and "the strength grade of cement used shall not be lower than 32.5MPa" are deleted.

In the polymer emulsion, the provisions in the original specification that the solid content should be greater than 35% and that special products should be preferred are deleted. Instead, it is added that their quality shall comply with the current national standard "Polymer Emulsions for Architectural Waterproof Coatings", which facilitates coordination with material standards.

In the polymer cement waterproof mortar, the content "shall be used up within 1 hour after mixing" is deleted and replaced with the requirement "shall be used up within the specified time", making it more in line with the actual construction situation.