Abstract
The main purpose of this study is to classify the rock mass quality by using rock mass quality (Q) and Rock Mass Rating (RMR) systems along headrace tunnel of small hydropower in Mansehra District, Khyber Pakhtunkhwa. Geological field work was carried out to determine the orientation, spacing, aperture, roughness and alteration of discontinuities of rock mass. The quality of rock mass along the tunnel route is classified as good to very poor quality by Q system, while very good to very poor by RMR classification system. The relatively good rock conditions are acquired via RMR values that are attributed to ground water conditions, joint spacing, RQD and favorable orientation of discontinuities with respect to the tunnel drive. The petrographic studies revealed that study area is mainly comprised of five major geological rock units namely quartz mica schist (QMS), garnet mica schist (GMS), garnet bearing quartz mica schist (G-QMS), calcareous schist (CS), marble (M). The collected samples of quartz mica schist, marble and garnet bearing quartz mica schist are fine to medium grained, compact and are cross cut by few discontinuities having greater spacing. Therefore, these rocks have greater average RQD, Q values, RMR ratings as compared to garnet mica schist and calcareous schist.
Highlights
The relatively good rock conditions are acquired via Rock Mass Rating (RMR) values that are attributed to ground water conditions, joint spacing, Rock quality designation (RQD) and favorable orientation of discontinuities with respect to the tunnel drive
Quartzite (QT) The average value of 145 MPa were calculated as Uniaxial Compressive Strength (UCS) strength for quartz mica schist (QMS) with RQD is 47%, joints spacing ranging from 10 - 20 cm, joints encounter are irregular, smooth and undulating-planar, persistence of joints are 6 - 4 m and joint apertures are
Tunnel was divided into five major geological segments on the bases of rock type: quartz mica schist (QMS), garnet mica schist (GMS), garnet bearing quartz mica schist (G-QMS), calcareous schist (CS), marble (M)
Summary
In this regard, a small hydropower project with 2.8 km long headrace tunnel was proposed in Mansehra district, Khyber Pakhtunkhwa. In many engineering projects including tunneling, ground excavation, foundations and slope stability analysis, geology plays a key role. Among these projects tunnel constructions require a considerable geological input [1]. Following parameters are used to describe and classify the rock mass into distinct classes: 1) Measurement of degree of jointing known as rock quality designation (RQD). Field studies revealed that study area comprised of five major rock units that have strong impact on the various properties of discontinuities including rock mass strength
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