Tunnelling work blamed for Israel sinkhole

Construction work on a new tunnel in Jerusalem has been blamed for the appearance of a sinkhole which swallowed three vehicles parked in a hospital car park.

Work on Highway 16 close to the Shaare Zedek Medical Center in the Israeli city has been blamed by the head hospital for the hole, which appeared on Monday afternoon. According to the Times of Israel, Dr. Ofer Marin said that the hospital was deemed safe and operating as usual.

Security camera footage from a nearby building captured the moment the sinkhole swallowed one car then two more moments later as earth and rubble fell into the chasm. There were no reported injuries.

Sinkholes occur fairly regularly, in the UK and elsewhere in the world. They are caused by large voids in the ground, and these voids can either be caused by natural or man-made mechanisms.

Former British Tunnelling Society chair Bill Grose said: “I’m not familiar with the situation in Jerusalem, but if there was a tunnel being constructed beneath or near to the sinkhole the engineers working on the tunnel should have a good idea about the ground conditions and their construction activities and hence have an opinion on the cause of the sinkhole.”

Some types of ground are soluble in water, and the passage of rainwater, which is often slightly acidic, through for example chalk or limestone can, over time, cause voids. Natural caves and potholes are created in this way.

Grouse added: “Man-made holes such as tunnels and shafts can result in sinkholes if more soil is removed during excavation than is required to install the lining. For example, it is possible for unstable ground to flow towards a TBM and be removed during the tunnelling process creating a void larger than the swept volume of the TBM.

“Tunnellers are aware of that risk and there are of course precautions that they take to avoid that happening.”

Independent tunnelling consultant Martin Knights, who is also former president of the ITA, said: “It is difficult to say what is the specific cause in this particular incident, but the tunnel is near enough [to the sinkhole] to warrant scrutiny.

“This happened on some metro projects in cities in Europe in the latter part of the 20th century and also particularly in China on metro projects during the early 2000s either above or adjacent to ongoing tunnel construction.”

Source https://www.newcivilengineer.com/latest/tunnelling-work-blamed-for-israel-sinkhole-09-06-2021/

Department of Civil Engineering https://www.ibu.edu.ba/department-of-civil-engineering/