A geomechanics classification for the rating of railroad subgrade performance

The type of subgrade of a railroad foundation is vital to the overall performance of the track structure. With the train speed and tonnage increase, as well as environmental changes, the evaluation and influence of subgrade are even more paramount in the railroad track structure performance. A geomechanics classification for subgrade is proposed coupling the stiffness (resilient modulus) and permanent deformation behaviour evaluated by means of repeated triaxial loading tests. This classification covers from fine- to coarse-grained soils, grouped by UIC and ASTM. For this achievement, we first summarize the main models for estimating resilient modulus and permanent deformation, including the evaluation of their robustness and their sensitivity to mechanical and environmental parameters. This is followed by the procedure required to arrive at the geomechanical classification and rating, as well as a discussion of the influence of environmental factors. This work is the first attempt to obtain a new geomechanical classification that can be a useful tool in the evaluation and modelling of the foundation of railway structures.

Geotechnical Engineering

Geotechnical analysis below the surface of hydropower plant is one way to determine the stability of the opening holes in determining the supporting system. A discussion about supporting systems cannot be separated from the analysis of the construction of recommended supporting system based on the weighting value of the geomechanical classification of the RMR and Q-System. The aims of this study are: 1) understanding the quality and class types of rock, 2) determining the supporting of RMR and Q-system, 3) understanding the safety factor of opening hole using Phase2. This study was carried out by recording data directly in the field, which later were used to determine the number of rock bolt needed in the installation of the supporting. Based on geomechanical classification, the rock mass in headrace tunnel adit 1 up stream has an average RMR value of 58 (moderate rock quality) and Q-system value of 4.06 (moderate rock quality), while adit 2 up stream has an average RMR value of 47 (moderate rock quality) and Q-system value of 2.30 (poor rock quality). Based on these geomechanical classification data, each type of supporting types is obtained. Supporting headrace tunnel adit 1 and 2 type, RMR value of type 1 can be applied to the RMR (60-80). RMR value of type 2 can be applied to the RMR (40-60). Supporting headrace tunnel adit 1 and 2 type, Q-system value of type 1 can be applied to Q-value (4-10). Q-system value can be applied to Q-value (1-4). Based on the modeling results using phase2, the total displacement of headrace tunnel adit 1 up stream is 0.92 cm with safety factor value of 1.20 and the total displacement of headrace tunnel adit 2 up stream is 1.17 cm with safety factor value of 1.04.