A Case Study
|Consultant||:||Design Tree Service Consultants Pvt Ltd|
|Solution for basement waterproofing||:||Fosroc Chemicals (I) Pvt ltd|
Key Challenges at project site
Project is designed for 3 basements approximately -12mt. Below ground level, water table is very high which demanded installation of 4 Pumps of 62 hp and 16 bore wells dewatering at the rate of 400lit/minute. Rainy season posed its own problem aggravating the site condition for project execution.
- City is located in the costal belt and prone to cyclone attacks and the nightmare came true when cyclone “Thane” hit the city in December 2011.
- Sandy soil substrate poses threat of differential settlement of raft foundation, and also possibility of collapse of benching done for basement excavation.
- Retaining wall flushed with the secant piling posing unique challenge for installation of waterproofing system in the absence of working space.
Challenges for the selection of suitable waterproofing system
Consultants M/s Design Tree Service Consultants Pvt Ltd and the clients BVR Mall were keen on waterproofing solution which can address effectively the basement waterproofing requirements of the project.
- They were looking for a right solution which can address the following issues:
- Dewatering: Dewatering system shall be in place and continuous till they complete the raft concreting which demands for installation of perforated pipes and pressure relief valves which could be taken across through the membrane.
- Easy cleaning: During power failure, rains & cyclones lot of slush can deposit on the waterproofing membrane, collapse of benching can deposit sand on the membrane.
- Differential settlement: Sandy soil substrate can lead to differential settlement of the foundation below raft.
- Time and cost Saving: Protection screed on the Waterproofing membrane and re-profiling of secant piles surface using shotcreting should not be mandatory since this activity demands additional time and cost.
- Easy and rapid Installation of waterproofing system: Waterproofing should be a parallel activity and go along with concreting rather than an independent activity for saving time.
- Positive side waterproofing: Waterproofing for retaining wall shall be installed from positive side in the absence of working space.
Fosroc Innovative & Engineered Solutions: Proofex Engage system
After detail discussions and study of project requirement, Fosroc was rock solid confident of providing right solutions to this basement waterproofing.
- Fosroc key success was routed by addressing solution to the issues as below.
Fully bonded system with mechanical bond to poured concrete with non-tracking property, unique mesh provides water tightness for every square mm of concrete, membrane stay in place in case of differential settlement of raft foundation.
- Thickness of the membrane is minimum 4mm, enabled direct placing of re-bars on the membrane without protection screed saving time and cost of protection screed.
- Easy and rapid installation of the membrane just by unrolling the membrane of 1.27mt X 30mt and overlapping using selvedge inbuilt with the membrane, waterproofing goes along with concreting.
- Pre-applied system enabled installation with minimum surface preparation even on wet condition.
- Mechanical bond, no limitation like difficulty or improper removing release film from membrane which affects chemical bond with concrete and possibility of bond failure due to dust, sand and slush due to rains or flooding. Sand and slush shall be cleaned using air and water jet.
- Simple and effective joint detailing for pressure releasing valves piercing through the membrane made easy using standard accessories.
In absence of working space, membrane fixed to the sacrificial shuttering provided on the secant pile for achieving positive side waterproofing, eliminated the demand for re-profiling of secant piles with shortcreting, reused ply was used for re-profiling of the secant piles.
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