Maramarua coalfield, Kopuku sector mining study. Geotechnical summary report

This report presents a preliminary assessment of Geotechnical and Hydrogeological conditions relevant to mining the Kopuku Sector of the Maramarua Coalfield, located at 90km southeast of Auckland. The investigations have been directed primarily towards opencast mining, with lesser attention to underground mining in areas of deeper overburden cover. The study was terminated on September 19, 1986. The planned geotechnical and hydrogeological studies have not been completed. The objective of this report is to summarise those studies which have been completed, and to provide preliminary conclusions relevant to mining. The studies include: Drilling and geotechnical logging of four vertical cored boreholes, geophysical logging of 52 exploration boreholes including the four cored boreholes, field testing of bored cores with point load and hardness index testing, laboratory testing of selected core samples including moisture content, attenberg limits, bulk density, slaking index, unconfirmed compressive strength and sonic velocity, triaxial shear and ring shear testing of selected core samples, gas emissions, measurement of standing water levels in open boreholes and installation of piezometers in one borehole.