Features, News

Alasdair Webb: Leading an innovative approach to landslide management

 

Alasdair Webb is the latest recipient of the IQA’s Excellence in Innovation Award – for leadership and strategic planning that enabled Holcim Dubbo Quarry to successfully prepare and predict a potentially catastrophic landslide that struck the site in 2019. Nickolas Zakharia reports.

In the children’s book Who Sank the Boat? by Pamela Allen, five animals attempt to fit onto a rowboat, one by one, making it gradually sink. A mouse causes the boat to capsize, despite making the smallest impact. Like the “straw that broke the camel’s back” maxim, this story tells us not to wait until it is too late to notice an arising problem. 

“Something small is an indication that there’s something big that’s wrong,” Holcim Dubbo Quarry manager Alasdair Webb tells Quarry. “It doesn’t matter what it is, whether it’s a structural problem, an electrical problem or a safety or health issue of any kind. Quite often there are small warning signs that you need to pay attention to and take heed and act and do something about. Many big failures, no matter what, you can forecast them by a lot of small things going on, you have just got to be in tune with what’s going on in order to be able to recognise those signs.

“Issues are like Swiss cheese, there’s lots of holes in everything we do but when these holes line up they can add up to a big problem. You can have lots of small issues every day but sometimes they can add up to something big. You have to recognise those small issues may interconnect and act on them to stop the unwanted outcome before it happens.”

Alasdair Webb (right) receives the IQA Innovation Award, sponsored by Trimble, from Dale Cameron, the Australian regional manager of Trimble Aggregates & On-board Weighing.

When a landslide struck the Holcim Dubbo Quarry in February 2019, the quarry had been vigorously preparing for it in the months prior – all from the moment that a supervisor noticed tiny cracks in the roadway above the site’s pit. Fortunately, Holcim Dubbo Quarry had known of a potential landslide at this point after a 2017 Xstract geotechnical survey was conducted on the site.

“In this case we could’ve just ignored the cracks and warning signs but I wanted to actually quantify the movement,” Webb said. “Once we saw that it was a problem we got into surveying and we managed it right the way through to the landslide.

“We have a thing called a slope stability checklist but we are always looking for things that are out of the norm – unusual things and such is the culture of the company. Every month we complete a number of different checklists and observations around the place and this was just something a keen eye happened to notice.”

RESPONSIBLE INNOVATION

Webb, who received an IQA Excellence in Innovation Award for his work in managing the potentially fatal landslide, now has another trophy to add to the already extensive list of accolades he and the quarry have received ranging from people excellence to innovation. In 2017, Webb was presented with an IQA Quarry Manager of the Year Award. 

But his new innovation award is perhaps the most important to date. Webb wanted to show the world what quarry managers do behind the scenes that goes unnoticed. 

“I think it’s significant for all quarry managers,” he said. “Quarrying is a very innovative job – it’s a very responsible job. And the reason I chose to write about it and submit it is that it’s one of those things as quarry managers we often do and just take in our stride.

“In this case I wanted to tell people about what we did. The actual principle was very, very simple. Just employing very simple techniques allowed us to manage and contain something that could have been catastrophic.”

After the cracks were noticed, the access road was closed, and Webb and his quarry team got to work on constructing a bypass road. They also planned to quantify the movement of the cracks, which meant measurements had to be taken. 

“When the supervisor first noticed the cracks in the ground, they were very small and we couldn’t tell whether they were moving or not,” Webb said. “For a long time, they weren’t moving very much at all and it was imperceptible for the naked eye or for just the casual observer to notice any difference.

“I talked to a surveyor who came out to look at the site. He then prepared a plan to go forward to monitor it. And that consisted of marking out a chainage every 25 metres along the area that was looking like it was going to fail.”

The contract surveyor used a theodolite – a rotating telescope for measuring horizontal and vertical angles – to detect the angles at which the ground was moving.

“We marked the chainage out every 25 metres and put a mark on the road and designed a triangulation style survey grid, where the surveyor could put his theodolite each time he came to set up,” Webb said.

Two trenches were also dug across the extension cracks at the top of the quarry pit to pinpoint the weak spot between the hanging wall and foot wall. The survey design was unique to Holcim Dubbo Quarry.

Trenches were dug at 90 degrees to the cracks in the roadway.

INEVITABLE LANDSLIDE

From December 2018, the surveyor took measurements every Tuesday and Thursday morning until the landslide occurred in February 2019 as predicted, along the plane of weakness that was dug up in the two trenches. 

“We did have quite a lot of time where we were able to extract the rock from underneath and this method allowed us to do that,” Webb said. “When we saw the ground starting to accelerate and move faster, we were then able to make the informed decision and remove our equipment from underneath. And then it was several days later that the land failed.

“If we hadn’t been innovative and come up with this method we wouldn’t have known – we would have just stood there watching and wondering.” 

Innovation is something that has been part of Webb’s 33-year quarrying career. Keeping things simple and breaking down roles can help solve problems more effectively – or as Webb describes it, “horses for courses”. 

“You can be innovative on just about anything and everything,” he said. “There’s always a better way to do things. One thing about quarrying is you can try something; if that doesn’t work, you can try something else. You’ve always got to have your wits about you and look for other ways to do things.”

A map showing the landslide in Holcim Dubbo Quarry.

And that proverb has remained true following the initial landslide. Webb believes there is potential for the material in the landslide to be recovered and reused for multiple applications.

“There’s still aggregate quality material, top quality material at the base of the landslide and then there’s some lower grade material that can be used for the production of certain products,” Webb said. “There will also be some material that we can use as general fill – ie  used in order to sculpt the landslide back to a stable and usable landform.”

As for the prize money from the award, Webb is hoping to use it to travel and attend one of the United States’ trade shows next year. “I’m particularly keen to go somewhere like the US to see what’s happening in the cutting edge of quarries over there,” he said. 

Webb credited his staff for the success of managing the landslide, saying it’s vital to have extra eyes and ears on site. 

“I know in the world of a quarry manager that we are so busy doing so many different things that often those small details often get overlooked and that’s why it’s really good to have good supervisory staff,” he said. “The best thing you can have is good quality supervisors and leading hands. You can’t be everywhere, notice and do everything but certainly getting that information from the field is invaluable.”

Look out for the full feature in the June issue of Quarry.

Leave a Reply

©2019 All Rights Reserved. Quarry is a registered trademark of Prime Creative Media.