What many people may not know is that the drillers and engineers of Boart Longyear have been involved in some exciting historical drilling projects in a variety of other applications, too. Drilling equipment for moon exploration is one such example (read Drilling Beyond Earth); but closer to home, the company has assisted with projects to explore and define foundation and structural integrity below the earth or even under bodies of water.

In the late 1920s, members of the Longyear team were contracted to test drill the route of a proposed vehicular tunnel under the East River to connect Manhattan to Brooklyn in New York, USA. The tunnel was intended to reduce transportation congestion due to the slow and unreliable ferry service that existed at the time. The Longyear company provided preliminary boring samples used to determine what was beneath the surface of the river. Characterizing the samples’ type of rock and its hardness allowed geologists and engineers to determine what equipment should be used for tunneling, how long it should take, and at what cost. Although the initial tunnel project didn’t receive support and funding, it laid the groundwork for a later project—the Brooklyn-Battery Tunnel—which was started in 1940 and opened in May of 1950.

A similar challenge of traversing a wide body of water required assistance from the Longyear team in 1929. Joseph B. Strauss, a visionary engineer, was tasked with his team to design the proposed Golden Gate Bridge in San Francisco, California, USA. As chief engineer, Strauss requested the services of Longyear to investigate the rock formations beneath the San Francisco Bay where the bridge would be constructed. Longyear started boring in the Bay in November 1929 along the sites of the proposed piers and anchorages. [i]

Due to the turbulent waters of the channel, the drillers had to be creative as to how they would retrieve the core samples beneath the tumultuous surface. Strauss was big on safety, requiring bridge workers use safety lines, work over safety nets, and even wear some of the first hard hats. The Longyear crew constructed a platform over the water supported by a boom—an A-frame—and guy-wires anchored to the shore. The platform allowed the team to suspend their drilling equipment securely on top and safely above the bay. Despite the problems of deep water, ocean traffic, storms, and tidal movement, the team was able to finish the work on schedule with complete core sample recovery.

The geological samples and subsequent data supplied to Strauss proved that the rock formations could bear the weight of the foundations and enable the huge bridge structure to be built. The information was provided in a full report to the board of engineers in February 1930 and the bridge was determined to be “feasible economically and structurally.”

This great news meant Strauss and his design team could move on to the next phases of engineering and constructing the Golden Gate Bridge. In gratitude for Longyear’s contribution, Strauss wrote, “The work done by your company, having been entirely satisfactory, and the relations between us and your drillers having been cordial and pleasant, I am glad to make immediate payment of the balance due.” [ii]  

Payments received by the company totaled close to $15,000 for the boring contract. It wasn’t for another three years (January 1933) that construction began and a groundbreaking ceremony for the bridge was held. The Golden Gate Bridge was completed in May 1937 at a total cost of $35,500,000.

Click below images to view larger.

From left to right

Images 1 and 2: “Engineers Speed Plans for Golden Gate Bridge” - A Pacific Street and Road Builder article from March 1930 stating “test borings reveal solid rock foundations and showing a photo of boring operations at the Lime Point side of the bridge in Marin County, California.

Image 3: “Borings Started for Gate Span” – Photos shows in the Vallejo California Chronicle, Sebastopol California Times, and Cresent City Triplicate newspapers on November 29, 1930. The article shows a photo of Longyear’s diamond-tipped drills used for bore sampling the rock at the San Francisco end of the bridge, next to Fort Point.

Image 4: “Getting Down to Bedrock” – A San Francisco Examiner article, dated February 14, 1930, picturing engineers, including Strauss, inspecting boring samples from the Golden Gate Bridge project.

A truck-mounted LS600 sonic rig taking core samples near a dam site.

Shortly after the Golden Gate boring project, the Longyear company became involved with drilling projects for the construction of hydro dams around the country. In the 1930s, Longyear drillers did test borings for several of the twenty planned dams under the jurisdiction of the Tennessee Valley Authority. These dams were part of a comprehensive plan for the reclamation and development of the Tennessee River—covering an area of more than forty thousand square miles and over seven states.[iii]

Later twentieth-century construction-type projects for Longyear drillers included boring for core samples for the Missouri River Project, and the first foundation test borings for the Fort Peck Dam in Montana—the project’s first major hydro dam.

Today, Boart Longyear continues to assist with construction and rehabilitation projects around the world using even more advanced technologies and equipment. The company regularly uses sonic drilling technologies which are ideal for avoiding many of the challenges experienced with conventional drilling methods.

Sonic drilling offers quality control in conjunction with the production and installation of geotechnical construction elements. The sonic method can actually eliminate the need for circulation-type drilling allowing the driller to work safely in situations that involve sensitive structures, vulnerable site conditions, difficult geology, or have restrictive conditions. Sonic drilling also provides measurements and samples to evaluate actual conditions across a given site during the progress of exploration and construction.

A few examples of Boart Longyear’s sonic drilling assistance with tunnel, bridge, and hydro dam projects in the twenty-first century include: [iv]

• Casing installation for the Boston Central Artery / Tunnel Project CO9A4, Massachusetts, USA. As part of the process of installing three jacked tunnels under the 13 railroad tracks at South Station in Boston, specialized sonic drilling was used to install casing through some of the most difficult combinations of historical fill materials—steel rails, brick tanks, woodpiles, granite seawalls, reinforced concrete slabs, track ballast rock, clay, stratified sands, till and weathered bedrock.

• Installation of a grout curtain at Clearwater Dam in Missouri, USA. The project required a drilling method with the ability to penetrate and sample both the body of the dam and its foundation without the use of air or water circulation. Sonic drilling was used to investigate a deep sinkhole and affected a remedial plan involving drilling 15-degree battered grout holes through embankment fill to construct a grout curtain.

• Sonic drilling comparison for a tunnel design pilot study on the Combined Sewer Overflow Control program, Anacostia River Project in Washington DC. Sonic drilling was used to perform continuous soil coring with approximately 100% core recovery and careful installation of multiple piezometers.

• Micro-pile installation testing near the Holland Tunnel in New Jersey, USA. Sonic drilling was compared with conventional drilling to advance micro-piles through silty sand overburden, overlying till, and schist. Not only was the sonic drilling 33% quicker for installation of the micro-piles, waste was also eliminated to nearly the volume of the sonic core, which minimized disposal costs. 

Bridges, tunnels, dams, and even buildings are all safer because of the work done to investigate, test, and secure the foundations. Although considered a small contribution to these engineering marvels, Boart Longyear employees are proud of the heritage the company has earned and its involvement in each part of history.

For more information on Boart Longyear’s construction drilling capabilities, including sampling core, anchoring, micro-piling, jet grouting, and ground freezing, visit the overburden and construction tooling section.

[i] https://www.goldengate.org/bridge/history-research/bridge-construction/joseph-strauss/

[ii] Edmund J Longyear, and Walter R Eastman. 1984. “The Mesabi and Beyond”; Pg 181

[iii] Edmund J Longyear, and Walter R Eastman. 1984. “The Mesabi and Beyond”; Pg 192

[iv] George R Burnhart, Boart Longyear Technical paper. 2006. “Sonic Drilling Offers Quality Control and Non-Destructive Advantage to Geotechnical and Construction Drilling on Sensitive Infrastructure Sites.”

Golden Gate Bridge Photos from historical records, the Golden Gate Bridge, Highway and Transportation District and found here https://www.goldengate.org/exhibits/engineering-the-design/

Golden Gate Bridge Photo courtesy of Umer Sayyam

Boart Longyear historically named their overburden and construction drilling products line for this type of drilling “Delta” tools. In addition to being the fourth letter of the Greek alphabet, and a code word representing the letter D, (used in radio communication), delta is also defined as the difference between two things or values, or the average change of any changeable quantity. In short, the overburden construction drilling product line was designed for drilling through changing ground conditions typically encountered above bedrock.

With more and more challenging and larger specialty geotechnical construction projects in difficult, complex, and varying ground conditions, rotary and percussive drill rigs in the construction industry were getting stronger and more powerful. Bigger, stronger, and more powerful rigs subsequently required larger, stronger, longer-lasting construction drilling tools – including better designed and manufactured casing bits.

Casing bits are used in deep, difficult overburden when a casing shoe is not sufficient to drill to depth. There have not been any significant advancements made in casing bit designs since the 1990’s. The so called “proven, bullet-proof” bits were made day after day without questioning the physical mechanics or what might be possible with a new or improved design.

In light of this, Boart Longyear decided to partner with its customers to look at redesigning casing bits in the geotechnical construction drilling field.

The first discovery in this initiative was that drilling site feedback often compared apples to oranges about bit designs and there was no real definition of drilling bit designs or any so-called standard. The sum of differing opinions needed more segmentation and analysis. After interviewing customers, experienced drillers, and engaging our internal engineers, all of the feedback was segmented and combined with proven manufacturing information and our new Z Design casing bits were created, tested, and are now available to the industry.

Combining the three main aspects in faster and longer lasting casing bits: cutting, flushing, and gauge protection, Z Design casing bits provide improved flushing, faster ROP (rate of penetration), and longer lasting bits. The difference is in the design and materials. Using premium tungsten carbides, high quality steel, improved gauge protection, and induction brazing to reduce blistering, Z Design casing bits are manufactured in our ISO-Certified, Eiterfeld, Germany manufacturing plant.

CONSTRUCTION

Casing bit bodies are constructed of high strength quenched and tempered steel. The high-quality tungsten carbide inserts are induction brazed into the steel bodies ensuring a secure fit without overheating issues associated with flame brazing. Strict machining control of the carbide seats prevents premature loss of carbide inserts.

GAUGE PROTECTION

Tungsten carbide gauge protection on casing bits prevents excessive wear on the outer diameter of the bit in abrasive ground conditions. Additionally, in unconsolidated conditions where the ground is caving in on the drill string, gauge protection assists in freeing the bit and casing by providing another cutting surface.

SHRINK FIT CARBIDES

When required, Boart Longyear offers shrink fit installation of all hemispherical, ballistic, and two-step tungsten carbide inserts instead of the standard induction brazing. This very precise construction method is often utilized when drilling in extremely hard ground conditions and provides both increased button retention and longer overall life.

ADVANTAGES

• Computer controlled induction brazing of tungsten carbide inserts for superior process control and overheating prevention, common with flame brazing
• High-grade body construction with quenched and tempered steels
• Optional tungsten carbide gauge protection available for unconsolidated grounds and increased bit life in abrasive conditions
• Specialized designs for unique drilling situations such as drilling through reinforced concrete and drilling without inner bits.

Better casing bits means better drilling outcomes and ultimately results in better ROI (return on investment). Casing bits are designed for rotary percussive or rotation only drilling based on the tungsten carbide inserts utilized as well as the geometry of the bit. Customized tools for unique drilling applications are also available upon request.

Contact your local Boart Longyear representative or distributor to order the best casing bits in the overburden drilling market. Still not convinced? Contact us for help designing and implementing a testing drilling program to prove using Boart Longyear casing bits have a higher ROI.

For part numbers, download the Boart Longyear Overburden and Construction Tooling catalog here.

The most common practice, in this case, is to drive T45 or T38 rods for percussive drilling and API rods for rotary drilling. But when the customer was drilling with top hammers, his drillers had to change the complete tooling setup from API rods to percussive rods and vice versa. This proved to be ineffective and was burning resources on job sites and in tooling stock. The customer came to Boart Longyear for a rod solution that would be able to drill both rotary and percussive without changing the tooling set up.

Our engineers designed the new CBXP rods capable of both rotary and roto-percussive. By using the new rods, the customer reduced his spend on drill rods by 60% annually, purchasing one dual-purpose CBXP rod, instead of having to buy twice the number of rods for the two types of drilling. Productivity on job sites increased as changing tooling between the two different drilling applications was unnecessary.

CBXP drill rods are designed to be used as inner drill strings in double-head drilling applications. CBXP rods offer a more robust design than the common API rod and outperform API rods in durability and performance, especially when occasional percussive drilling is involved. It combines the effectiveness of an API rod but comes with more advantages than T38 and API rods, like:

• Higher flushing for higher penetration compared to API
• Longer thread life with an asymmetric thread profile
• Can be used for roto-percussive drilling (e.g. drilling though overburden boulders)
• Higher outside diameter compared to T38 & T45 rods results in higher flushing speed
• Conical thread shape provides better alignment for quick and easy make and brake
• Dual drilling capabilities as it can be used in both rotary and percussive applications

CBXP drill rods are primarily intended for use in rotary and rotary DTH drilling applications but are also commonly used as the inner drill string on double head rotary-rotary applications or in a single head rotary duplex application. CBXP may also be used for smaller percussive drilling applications. The rod ends of our CBXP rods are constructed of high tensile strength quench and tempered steel and are gas nitrided to provide additional life. Rod ends are friction welded onto mid-grade mid-body material. CBXP rods are manufactured in a variety of lengths and wall thickness. Boart Longyear can manufacture alternative rod lengths and spanner flats upon request.

Boart Longyear began manufacturing overburden and construction drilling products in 1989 at its facility in Germany to serve the foundation construction market. Boart Longyear overburden and construction tools were quickly recognized by the industry as reliable and well-designed. From the start, customers appreciated the use of high-quality steels, precise heat treating and thread gauging as well as the development of new tungsten carbides for the drill bit line. The attention to detail with the overburden and construction drilling tooling product line has made Boart Longyear one of the most respected names in the industry.

Today, Boart Longyear manufactures a broad offering of overburden and construction tooling at our 5000 m2 (54,000 ft2) facility in Eiterfeld, Germany. The modern ISO9001-certified facility hosts an array of advanced manufacturing capabilities including CNC (computer numerical control) machining, friction-welding, and induction hardening equipment for rod and casing products, as well as computer controlled ovens for assembly of tungsten carbide-tipped bits and tools.

Check out the full-line of Boart Longyear overburden and construction tooling by downloading the catalog.