How to classify the hardness of rocks encountered in drilling for water

The schedule of this article is the classification table of the hardness of rocks published in the specifications of engineering geology, which is a great reference for hydrological exploration or geological drilling for water, and is appended here for your reference.

The very soft rocks, soft rocks and softer rocks in the table are not brittle according to their mechanical properties, and the fissures are generally not developed. Whether there is water in the drilling and water extraction mainly depends on the lithological combination of the underground, i.e. the key lies in whether there are brittle rock interlayers in the strata.

The harder rocks and hard rocks in the table include both brittle rocks and rigid rocks that are not easy to crack (such as the common black hornblende), whose water-richness depends more on whether a fractured low-value anomaly (i.e., tectonic fracture) or a lithologically abrupt layer can be found with good misalignment retesting consistency. (The slate described in the table is included in the harder rocks, but it is not brittle enough to contain water well in many places because of the thin slate and many fine-grained sericite on the slate face).

There are three major categories of rocks, but carefully divided into thousands of species, the specific number of species who can not count, it is impossible to list them all in the table, it is only possible to list a part of the common rocks as a representative, can be cited.

It should be noted that the same kind of rock, the degree of hardness and rigidity and brittleness, flexibility vary greatly, which is closely related to the composition of the mineral composition of the rock, structural structure, which is the regional variability. It can be judged specifically according to the drilling speed and the friability of fresh unweathered rocks struck with a hammer. The degree of weathering of rocks is divided into five categories: fully weathered, strongly weathered, moderately weathered, slightly weathered, and unweathered, and the hardness varies greatly depending on the degree of weathering (you can carry a geological hammer with you to judge when you are in the field).

The lithological conditions are crucial to the volume of water. Lithology is the basis, is the internal cause, the external cause through the internal cause to play a role. Of course, it also depends on other hydrogeological conditions, such as topography, regional structure and drainage conditions. Different conditions of water is different, but what is a good point of water, what is a bad point, how to remove the coarse to extract the essence, to remove the false to keep the true, these issues are common law. Summarize the experience is to look for commonalities, and then use the commonality to guide the personality, with theory to guide the practice.