No Dig 2017

Cheng wins award for borehole research during HDD

Cheng wins award for borehole research during HDD

28 February 2017 , , 0

Mr Yuanze Cheng was awarded the ISTT Student Paper Award for his entry titled ‘Evaluating Method for Borehole Stability and Surface Movement during Horizontal Directional Drilling’ culminated in new methods for calculating maximum drilling fluid pressure and surface movement in horizontal directional drilling (HDD) projects.

Mr Cheng’s award-winning submission focused on the issue of borehole instability and excessive surface movement during the HDD process, which has become a growing concern during HDD operations.

Frac-out, or collapse of the borehole, and fluid loss caused by borehole instability and excessive surface movement, can have a negative influence on the overall project, as well as resulting in potential environmental impacts. Subsequently, investigating methods to predict maximum allowable drilling fluid pressure and surface movement is important.

He developed a new analytical model to predict the maximum allowable drilling fluid pressure during the HDD process, which considers the influence of soil softening impact. The model also provides an invaluable method for estimating maximum drilling fluid pressure during HDD projects.

A new analytical model to calculate ground displacement during the HDD process in a shallow soil environment was also developed and considers parameters such as different depths of cover, borehole diameters and different soils.

Mr Cheng conducted a series of numerical simulations to study these influencing factors and their effect on the plastic zone development around the borehole and the value of maximum drilling pressure. Field tests on maximum drilling fluid pressure and surface movement were designed and were also conducted to confirm the model.

The borehole instability mechanism, influence of the drilling fluid type and depth cover of borehole on maximum drilling fluid pressure were researched with the use of field tests. A method and criteria to evaluate borehole stability and surface movement was developed using analytical solutions, numerical simulation and field tests.

Mr Cheng has spent time in the field shadowing a HDD contractor in Chicago, Illinois and Phoenix and Yuma, Arizona to test if the new methods can assist contractors to complete HDD projects and deal with potential field problems more economically.

This article was featured in the Winter 2017 edition of Trenchless International. To view the magazine on your PC, Mac, tablet, or mobile device, click here.

If you have a project you would like covered in Trenchless International contact Assistant Editor Nick Lovering at nlovering@gs-press.com.au

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