Piling Canada

The Science – and Art – of Geostructural Engineering

Working as a team to identify and solve complex challenges requires both discipline and creativity
Written by Barb Feldman
December 2018

Working as a team to identify and solve complex challenges requires both discipline and creativity

Since 1972, when Brian Isherwood founded his one-man shoring and foundations design firm, Isherwood Geostructural Engineers (IGE) has continually evolved, refining and expanding its specialized services to include analysis, review, field inspection and monitoring of foundations and excavation support.

The IGE team now comprises more than 50 people in two offices – Mississauga, Ont., and Burnaby, B.C. – and has been involved in more than 2,400 temporary and permanent earth retention and foundation-system projects throughout Canada, the U.S., Mexico and the Caribbean. These have included the large circular-cell cofferdam for the Sir Adam Beck Tunnel project in the Niagara River, most of Toronto’s subway and LRT works and many of Toronto’s landmarks, including the CN Tower, Rogers Centre, Maple Leaf Square, the Royal Ontario Museum, the Four Seasons Opera House, the Ontario Science Centre and Pearson International Airport.

Isherwood has built a reputation for innovative solutions for increasingly complex projects, “whether using tried-and-true methods or adopting the newest technologies,” said Nadir Ansari, CEO, Isherwood Geostructural Engineers. He noted that under Brian Isherwood’s watch, Toronto projects began using interlocking caisson or secant walls years before they were adopted elsewhere in the industry and that the company introduced small-diameter tight-access and low-overhead drilling solutions for deep foundations.

Isherwood also worked with contractors to introduce micropiles and anchored shotcrete (a Canadian invention first patented in 1970 as a ground-control method) and was among the first to recognize that soil-nailing as an earth-reinforcing technology was well-suited for the glacial soils and weathered rock of the Toronto area, and in 1989 designed the area’s first permanent soil-nail wall. The company also pioneered the use of anchored shotcrete to support the Brantford hospital excavation during its 2003 expansion, where its performance matched that expected of a conventional continuous caisson wall.

IGE has developed the expertise to understand the unique soil composition of any given project and predict earth and building movements related to excavations using the observational method based on its long experience, extensive site data records and its use of precision geotechnical instrumentation and monitoring, said Ansari.

“The quantum leap in monitoring technology gives us the ability to mitigate risk that simply was not available when I started in the industry 30 years ago” as Brian Isherwood and Associates’ first employee, he said. “It allows us to predict, with an unprecedented degree of confidence, that the shoring solution we recommend is the best option for our client and stakeholders.”

In 1973, Isherwood was one of the first to adopt the use of below-ground wall movement and strut load monitoring with inclinometers and strain gauges to confirm a design’s performance, safety and economy. Ansari notes that he still has the serial number of that first slope indicator – “Lucky 13!” – in the archives of Monir Precision Monitoring, which he established as IGE’s sister company in 2002.

“Correct placement of monitoring equipment to maximize data collection allows for the prompt review and reporting of results and ensures that potential issues are addressed at the earliest possible time,” he said.

A reputation for innovative solutions for increasingly complex projects

In 1993, IGE used monitoring to adjust the design as work progressed on the St. Clair River Rail Tunnel rescue shaft to retrieve and repair the giant 100-ton cutter-head assembly of a tunnel boring machine from nearly 100 feet below ground.

“The design-build team had to respond to site changes on the fly,” with a lack of accurate geotechnical information, significant ground loss and the clay soil around the tunnel losing strength, “under intense schedule pressure while a major civil engineering project was on hold,” Ansari said. That work, which was accomplished quickly and safely, earned the company the Deep Foundations Institute Best Project award for their design involvement. More recently, the company’s use of finite element modelling and electrolevel technology on a project adjacent to Toronto’s subway line, enabled it to predict the subway’s movements to within a millimetre’s accuracy.

“Cutting back on detailed soils investigation and monitoring increase the risk to all stakeholders – and, I would argue, cost the industry tens of millions of dollars annually,” said Ansari, and clients often get the firm involved at the earliest stage possible – often even before land is acquired – to help in decision-making and mitigate long-term risk.

IGE has archived each of its projects in an ever-growing GIS database, including information on what exactly has been unearthed, the unique systems the company has designed over a 45-year period and their subsequent real-world performance. It’s a “library” that represents hundreds of thousands of hours of experience.

“Before we provide a proposal for a client’s upcoming project, we can see how adjacent sites in our database behaved and know if we should tweak it one way or another – it’s a process of continual investigation and refinement,” and all part of the company’s due diligence homework, he said.

“When clients start to dig, we have to make sure our design considers the types of soil we are dealing with, water tables and what kind of urban infrastructure is underground,” Ansari said. “It’s quite possible you’ll have underground rivers, in a glacial area you could have boulders and on reclaimed land you know there can be existing rock cribs, structures and various other objects that complicate the design and construction. We research the site to minimize unpleasant surprises, but it is impossible to know exactly what and where they are.”

In Toronto, excavation has unearthed old timber building foundations and dock walls, cars and boats, a box of muskets, and even, at Pier 27 at the foot of Yonge Street, an old munitions shell from a Second World War ammunitions depot. “That stopped work – when you find these things unexpectedly, it just adds to the challenge,” he said, adding that alternative solutions are developed to address changing site conditions. “They keep us on our toes.”

Every site has unique constraints that benefit from creative thinking

Urban sites are getting tighter and deeper, and on many of the historical structures must be preserved, all of which means support, design and construction are ever-more challenging, Ansari said.

In the past decade IGE has designed many façade-support projects, including the King Blue project in the city’s downtown core, where shoring and support were required for a six-storey historical façade; the highest project of this kind in Toronto’s history, at the time. Due to the tight access, IGE’s design used micropiles for gravity and wind loads for the façade support structure, as well as lateral earth pressure loading for the excavation shoring wall. “An industry first, to my knowledge,” Ansari said, “with less than 14-inch diameter bored holes threaded between the existing utilities.

“With old buildings you never know what renovations they’ve had done, what beams they’ve taken out or what they’ve done to the brick or the window lintels. We are careful to build flexibility into our designs to suit actual conditions as they are uncovered during installation, which enables us to respond quickly and ensures safety of people and structures and continuity of work,” he said. “The important thing is to have a scheme that allows for tweaking, either adding support or taking it away if actual conditions are discovered to be better than predicted.”

IGE shares its findings with stakeholders and proposes the best course of action at “Red Flag Meetings,” where every entity involved in the project can ask questions and add their expertise in a completely transparent back-and-forth process, an industry first, says Ansari.

“All walk away knowing we’re on the same page and know the project challenges,” Ansari said. Leveraging everyone’s experience and expertise also allows IGE to evaluate on-site safety, check project timelines and keep client costs within budget, he added.

Clients often get the firm involved even before buying the land

Modern subsurface geoengineering is an art as much as a science, observed Ansari, noting that every site is unique and has constraints that benefit from creative thinking, “whether that’s evaluating soil ‘personality,’ developing shoring solutions that preserve buildings adjacent to or on the worksite or designing for tight spaces,” he said. Working as a team and identifying and solving complex challenges – often ones that clients didn’t even realize they had – all requires a kind of creative discipline,” said Ansari. “Techniques are continually improving and we’re constantly learning, project by project.”

Brian Isherwood, still a key company resource, created a culture of creative problem-solving almost 46 years ago and, “I still find the can-do attitude at Isherwood refreshing – you can always solve a problem when you put the right team together,” said Ansari.

The company’s technical excellence, practical knowledge, balanced designs, client engagement and longevity in the industry offers the “complete solution” for its clients, he said. “With can-do people, we can do just about anything.”  🍁

Category: Profile

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