BENGALURU: Passengers on the Purple Line faced severe inconvenience on Wednesday morning due to disruption in Metro services A BMRCL spokesperson said they could operate trains only on one track in the morning due to repair work at Trinity Station. “We had operated short loop services between MG Road and Mysuru Road stations as well as Indiranagar and Byappanahalli stations to reduce the peak hour rush,” said a BMRCL official. Normal operations were resumed around 10.20 am.Many passengers complained there was no advance information about the repair work and no announcements at stations. "The staff were clueless about the delay. They should have informed public about the repair work in advance. I had to take a cab from Indiranagar to Kengeri and paid 10 times the Metro fare,” said Nagesh A, a passenger. There were huge crowds and long queues at stations like Kempegowda and Byappanahalli. Several passengers could not make it to office on time due to the delay.Panic among passengersPassengers panicked after messages started doing the rounds that there was a tilt in a viaduct near Trinity Station. Many regular commuters were also afraid to use the Metro. “There were so many messages on social media about the tilted viaduct that my husband asked me to take a cab instead of the Metro,”said Anitha S, a passenger at MG Road. However, some passengers misunderstood ‘honeycomb formation’ as a gathering of honeybees and slammed BMRCL.BMRCL officials dismissed the rumours. “If it was tilted, then we would have stopped operations,” said an official.Traffic police had a tough time managing traffic near Trinity Station after several people gathered to take pictures. BMRCL barricaded the affected area which further shrunk the width of the road. BMRCL spokesperson BL Yeshwanth Chavan clarified there’s no twisting of any pillar. Meanwhile, BMRCL Employees' Union demanded a thorough probe into the structural flaw.Honeycomb effectConcrete honeycombing is caused by a number of reasons including poor cement-to-water ratio, placement of reinforcing bar that affects the oncrete from filling up well and imbalances in materials added. Experts said honeycombing can become a concern when steel is exposed. This can weaken the steel over time due to corrosion.BMRCL MD Seth said, “A detailed inspection of concrete is needed through non-destructive method to ensure it’s adequately strong. A raised steel platform is being erected duly blocking a part of the road so that engineers can carry out tests. The affected portion is very small and will not affect overall safety of the structure. The rests are being conducted as a matter of abundant precaution.”BMRCL will take up repair work after 11pm for the next few days. Chief minister HD Kumaraswamy, who is in Belagavi for the winter session of the legislative assembly, called up Metro authorities and asked them to expedite the repair work.A R Shantha Kumar, former dean, civil engineering, Anna University, Chennai, said: “The presence of a honeycomb is also an indication of poor quality of construction. The strength of the structure will be reduced if it is unattended”.Ultrasonic technologyBMRCL will conduct a survey along the 42-km Phase 1 network. Ajay Seth said, “We will use ultrasonic technology to detect honeycombs. The recent case cannot be attributed to low-quality work but we have decided to conduct more quality checks for Phase 2 structures at casting yards.”While honeycombs on sides and bottoms are visible to the naked eye, those inside concrete can be detected only by advanced techniques like ultrasonic testing. Honeycombs will reduce the load bearing capacity and water finds an easy way to reinforcement rods and rusting and corrosion starts. This will result in losing grip between rods and concrete which affects safety and life of concrete structures.What is a honeycombEmpty spaces are formed between concrete and reinforcement, mainly due to air bubbles and it looks like honeybees are based there and therefore its called a honeycomb.How it’s formed* Insufficient compacting or vibrating* Inappropriate water-cement ratio while mixing concrete material* If framework is not done properly or if it’s not rigidHow to prevent it* Framework should be in good condition before concrete is poured* Vibrate concrete while pouring it so it helps consolidation. Too much vibration may lead to shuttering oscillate and this causes concrete to bleed out* In places like beams, honeycombs are due to jumbling of reinforcement of beams and column rods at one placeHow to fix it* Concrete particles and loosened aggregates should be removed by using chipping hammer and wire brush* Should be cleaned thoroughly with wire brush to remove fine particles* Remove honeycomb area by chipping fresh concrete or cement grouting* Honeycomb chemical adhesive should be injected into spot* Ensure mix has sufficient fine particles to fill voids between coarse aggregateHow it affects* Reduces load bearing capacity of structure* Water and air enters concrete* Reduces durability of concrete* Rusting and corrosion of reinforcement occurs* Causes weakening of structural strengthTWEETSAnger and confusion* Waited for almost half an hour @ Vijayanagar metro station from 7:35am till 8am and there was no single announcement nor any message on the display board. All the people calmly waited for a train patiently-really appreciated that. Request to plan & communicate properly. Thank u.Rohan S Rao @rohansrao* BMRCL had to notify at night or early morning Without putting commuters into trouble. Many students who had exam were extremely troubled as they relied completely on metro for travellingSrinidhi S U @SRINIDHISU* There were no announcements in any of the station and staffs were not aware of the situation.. Maturity is required in metro operationNaveen @krn045* Should have been notified long before. There wasn't a single announcement at stations. And you tweet after 2-3 hrs. Anyway public would read in tomorrow's newspapers.Suresh Belgundi @sbelgundi* Metro Phase 1 construction is pathetic. One can see honeycomb in concrete structures all over.Prajwal @PrajwalByreshQUOTEAn inquiry has been conducted and experts said there’s no problem in running trains at a slower speed. However, I’ve asked them to crosscheck before taking a decision. I’ve been informed that the technical problem can be rectifiedHD Kumaraswamy, chief minister

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