Horizontal Drain Hole Programs for Slope Depressurization

Provider: BGC Engineering Inc.  


Horizontal drain holes (HDHs) are often an integral part of the geotechnical engineer’s toolbox when pit wall performance is affected by porewater pressures. HDHs are commonly used or proposed for open pit depressurization systems; however, data to support the design, installation and planning (along with costing) of these systems is often sparse, except perhaps for more advanced mining operations. Confirming the need for and planning of HDH systems for proposed open pits in greenfield sites is even more challenging. For operations that employ HDHs, there is often a poor understanding of the impact that the drains are having on the porewater pressures and the associated slope performance, commonly due to a lack of groundwater monitoring instrumentation within the vicinity of HDHs. Guidelines for the design, implementation, and monitoring of HDHs are provided by Beale and Read (2013); however, there is an opportunity to update and enhance the concepts presented in that book with data from operating mines. The aims of the proposed HDH study are to:

  • Conduct a survey of LOP III member companies and their operations, and other interested mining operations not members of LOP III, and report on the current state of practice of HDH implementation in open pits.
  • Develop empirical tools based on best practices to assist practitioners in designing, planning, implementing and maintaining HDH systems, with reference to real data and case histories.
  • Develop approximate planning and budgeting guidance. Guidance on budgeting will depend on willingness of survey participants to provide costs.
  • Provide recommendations for defining and verifying the success of an HDH program.
  • Contribute to the science behind HDHs by exploring the importance of “getting the hydrogeology right” and presenting simple analytical and numerical modelling tools that can be used to estimate HDH requirements at both brownfield and greenfield sites.
  • Provide an update to the portions of the book by Beale and Read (2013) that pertain to HDHs, where applicable, by means of a guidance document, which will presumably be published on the LOP III website