Measuring the water retention curve of rock fragments: A novel repacked core methodology

We describe a novel suction plate experiment that uses large, repacked soil cores comprising clasts and a fine‐textured matrix to accurately measure the water retention curve of rock fragments (RFs) of high and low porosity. The method incorporates a suction plate‐core containment system that can be weighed as a unit, to overcome typical core size restrictions. The method relies on analysing the relationship between total core volumetric water content and RF concentration. Cores are packed with a mix of glass and RFs to maintain a uniform volumetric total clast proportion of 30% while RF concentration varies. A constant total clast volume improves accuracy and precision by ensuring the water‐holding characteristics of the matrix varies as little as possible among cores. Highlights We determine the water retention curve of greywacke‐pumice clasts in large, repacked soil cores. A suction plate‐core containment system that is weighed as a unit allows large cores to be used. WRC is determined with cores of varying rock%, but total clast% stays constant by adding glass. By using the above, the WRC of low and high porosity rocks can be measured precisely.