Study and monitoring of the stability of a rock mass at the Dar-El-Oued tunnel, wilaya of Jijel – Algeria

Abstract

The construction of a civil engineering work requires many preliminary studies as well as various calculation methods to give an assessment or a forecast of the state of the rock in place and the behavior of the structure in its real environment and under various conditions (construction phase, service and operating phase). The present work concerns the access zone of the Dar-El-Oued tunnel, located on the national road n°43 about 40 km West of the city of Jijel (northeastern Algeria). The geotechnical study of this tunnel was carried out following the classification methods relating to underground structures. Through the results of this study we have determined the influence of land pressures on the mechanical behavior of the ground, which allowed us to measure the state of stress in the rock and to make a comparison between the results of the measurements of convergence and that of numerical modeling. On the other hand, the influence of the velocity of vibration induced by explosive shots has been discussed in order to check the stability of the face as the digging progresses. From the results obtained, it can be said that the surface displacements of the soil are relatively small compared to those determined by the numerical model at the level of the vault and the slab. Note the good agreement between the results provided by our numerical model and those obtained in-situ.

Study and monitoring of the stability of a rock mass at the Dar-El-Oued tunnel, wilaya of Jijel – Algeria

“…Tableau 1. Vitesses de vibration en (m/s) à partir de la distance du front de taille [4] Distance (m) 40 50 60 70 80 90 100 K = 1,2 0,12 0,08 0,06 0,04 0,037 0,030 0,024 K = 1,4 0,15 0,10 0,07 0,05 0,043 0,035 0,029 K = 1,6 0,17 0,11 0,08 0,06 0,049 0,040 0,033 K = 1,8 0,19 0,13 0,09 0,07 0,05 0,048 0,037 K = 2 0,21 0,14 0,10 0,078 0,062 0,05 0,04 K = 2,2 0,23 0,15 0,11 0,08 0,068 0,055 0,045 K = 2,4 0,25 0,17 0,12 0,09 0,07 0,06 0,049 K = 2,6 0,28 0,18 0,13 0,10 0,08 0,065 0,05 K = 2,8 0,3 0,2 0,14 0,12 0,09 0,075 0,06 K = 3 0,32 0,21 0,15 0,11 0,086 0,07 0,058…”

“…PK 134,079 [4] L'amplitude des déplacements prévisibles est déterminée par les calculs effectués au stade du projet. On retient rarement une valeur maximale admissible pour les déplacements, car l'amplitude des déplacements mesurés ne permet pas à elle seule de juger la stabilité de l'excavation.…”

Study and monitoring of the stability of a rock mass at the Dar-El-Oued tunnel, wilaya of Jijel – Algeria

“…4. Mesures de convergence sur le cintre n°1 au PK 134,079 [4] L'amplitude des déplacements prévisibles est déterminée par les calculs effectués au stade du projet. On retient rarement une valeur maximale admissible pour les déplacements, car l'amplitude des déplacements mesurés ne permet pas à elle seule de juger la stabilité de l'excavation.…”