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• Prof. Carol Livermore
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A New Prediction Model for Cutting Depth of Hard Rock Using High-Pressure Water Jets

• Original Paper
• Published: 05 May 2024

Cite this article

• Fuwei Liu 1 ,
• Yansen Wang 1 , 2 ,
• Xin Huang 1 ,
• Guoxuan Song 1 &
• Yuning Wang 1  

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High-pressure pure water jet has been widely used in breaking soft rocks and medium–hard rocks, but its research on cutting hard rocks is very limited. The cutting depth, as the most important index for evaluating the effectiveness of rock breaking by water jet, is difficult to be predicted accurately because of numerous influencing factors. This article aims to establish a concise and universal prediction model for the cutting depth of hard rock, including all variables that affect the cutting depth. Firstly, four types of granite and sandstone, which are difficult to break in engineering, are selected to investigate their cutting depth under the action of high-pressure continuous water jets. The rock physico-mechanical parameter that has the highest correlation with the cutting depth is found to be the shear modulus through tests. In order to reasonably evaluate the energy utilization rate of cutting depth of rock by water jet, the concept of cutting depth energy index (CDEI) is proposed. The jet pressure corresponding to the maximum value of CDEI is approximately 40–60% of the rock compressive strength. The idea of “moderate nozzle diameter, high traverse speed, multiple cuts” is put forward for cutting hard rock more efficiently using high-pressure water jet. Then, a new prediction model of cutting depth for high-pressure water jet cutting hard rock is established using similarity theory and dimensional analysis method, and the accuracy and reliability of the model are verified through experimental testing. The results of the study can help to improve the breakage efficiency of hard rock, and at the same time, provide a theoretical basis for the rational selection of high-pressure water jet parameters.

The concept of cutting depth energy index (CDEI) of rock subjected to water jet is proposed.

The most effective cutting technology method for cutting hard rock by water jet is proposed taking into account the cutting effect and specific energy consumption.

A new prediction model of cutting depth for high-pressure water jet cutting hard rock was established using similarity theory and dimensional analysis method

The primary variables affecting the cutting depth of hard rock are the jet pressure and the shear modulus of the rock

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Cutting efficiency of extremely hard granite by high-pressure water jet and prediction model of cutting depth based on energy method

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Acknowledgements

This research work was financially supported by the National Key Research and Development Program (Grant no. 2022YFC3005902), the Fundamental Research Funds for the Central Universities (Grant no.2021GJZPY15), the Graduate Innovation Program of China University of Mining and Technology (Grant no.2023WLKXJ189), the Postgraduate Research & Practice Innovation Program of Jiangsu Province (Grant no. KYCX23_2748).

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State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, 221116, China

Fuwei Liu, Yansen Wang, Xin Huang, Guoxuan Song & Yuning Wang

School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, 221116, China

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Liu, F., Wang, Y., Huang, X. et al. A New Prediction Model for Cutting Depth of Hard Rock Using High-Pressure Water Jets. Rock Mech Rock Eng (2024). https://doi.org/10.1007/s00603-024-03919-1

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Received : 13 September 2023

Accepted : 03 February 2024

Published : 05 May 2024

DOI : https://doi.org/10.1007/s00603-024-03919-1

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ST Engineering mechanics need wage increase | Guestview

V olkswagen auto workers voted for union representation at a Chattanooga plant recently with 2,628 workers voting for union representation, or 73 percent, and 985 against. This is the first foreign-owned auto plant in the South form a union, and it is a great win for working women and men in America.

Volkswagen can afford to pay fair wages, provide competitive benefits and honor union-worker protections after making $75 billion in profits the past three years.

What about the airplane mechanics at Singapore-owned ST Engineering in Pensacola?

I understand reluctance to embrace unions, as I have spent an aviation career having union dues routinely deducted from my paycheck. A wise man once said: “everybody hates unions, until they need one.”

The average annual salary for aircraft mechanics is $76,260, according to the U.S. Bureau of Labor Statistics. Florida has the second highest employment rate for aircraft mechanics in the country, where the average annual salary is $70,290.

Even though the city, county and state have handed out tens of millions in economic incentives to ST Engineering, we learned the median pay for employees was $47,109.40 – 40% below the national average – as ST Engineering sought more public funding for an expansion project that approved by the Pensacola City Council.

In case you missed it: PSC, Triumph could invest $12.3M into filling 'huge void' in aerospace workers

Aircraft mechanics are undercompensated in Pensacola. ST Engineering needs to increase wages to align with the importance of the work performed, job requirements and increased cost of living here. This is a highly skilled trade. Home prices in Tennessee, Florida and Alabama have increased significantly, and young people can barely afford to live as housing affordability dramatically impacts the middle class. The South is no longer an inexpensive place to live.

Volkswagen thanked workers for voting in the election. In Germany, corporations collaborate with unions and often include union representatives on corporate boards to assist with strategic corporate decisions.

Will a Singapore corporation take the same collaborative position? Better yet, will ST Engineering consider competitive wages and improved work rules for Pensacola-based employees?

This is a breakthrough moment for workers in the South.

Not surprisingly, there has been hostility from some elected officials. A few Southern governors signed a joint statement the week of the organizing vote, ironically, using scare tactics to oppose “misinformation and scare tactics (unions) brought into our states.”

It is no surprise to see this sort of labor hostility, which serves as a reminder of a long hostility toward basic worker rights in the South. But angst against labor unions is out of date and out of touch.

Workers and their families know wages have declined when adjusted for inflation. Job security and work rules seem non-existent in the gig economy. American workers deserve better, and there needs to be a change of mindset towards workers and their families. Workers should not be treated merely like full-time equivalents (FTE) balanced on spreadsheets against shareholder profits.

I know the benefits of unions. So do passengers on Cactus Flight 1549, a plane flown by Sully and Jeff Skiles that was forced to land in the Hudson River in 2009. Every trade in that miraculous landing and rescue was represented by a union – the pilots, flight attendants, and ferry crews. The police, firefighters and air traffic controllers. They all responded with the professionalism their unions insured they were trained for. The Miracle on the Hudson was union made.

Now more than ever, we need unions. They need to be more cooperative than in the past and interact with communities promoting the benefits of a healthy and appropriately compensated workforce. And we need corporations too. Executives need to be more humanistic and recognize people over profits.

John Herron is an airline pilot and was a legislative affairs representative and labor negotiator on behalf of airline pilots. He resides in Pensacola where he was a Navy flight instructor. He earned a Juris Doctorate from the Temple University School of Law and is a graduate of the U.S. Naval Academy.

This article originally appeared on Pensacola News Journal: ST Engineering mechanics need wage increase | Guestview