Assessment of tunnel portal stability at jointed rock mass: A comparative case study

Analytical and numerical assessment of a preliminary support design – a case study

“…Tunneling is known to disrupt the initial in-situ conditions, thereby altering the pre-excavation parameters (Satici & Ünver, 2015). Most rock masses at lower confinement levels reach their residual strength when strained significantly by exhibiting some post-peak strength losses.…”

“…The added joint elements only produce limited deformation without any detachment (Kulatilake & Shu, 2015). Continuum modeling assumes that the rock unit cannot be opened or broken and that the joint spacing is close or extremely close (Satici & Ünver, 2015). The majority of the discontinuities spacing in the study area varied between close to very close spacing.…”

Determination of Joint Surface Roughness Based on 3D Statistical Morphology Characteristic

“…e values of Z 2 , SF, and R p were determined with equations ( 1)-( 3), as shown in Table 3. e roughness of each profile can be calculated with equations ( 4)-( 6), and JRC p of the joint surface can be obtained based on the roughness of profiles and equations ( 4)- (6). JRC p (Z 2 ), JRC p (SF), and JRC p (R p − 1) calculated in x and y directions of four shear surfaces are plotted in Fig- ure 11.…”

“…Rock joints widely exist in rock engineering [1][2][3][4]. e mechanical properties of rock joints are considered as the controlling factors of rock mass engineering stability [5][6][7][8]. Previous research studies have shown that the roughness remarkably affects the friction angle, shear expansion, and peak shear strength of jointed rock mass [9][10][11][12][13].…”

Risk Assessment of Tunnel Portals in the Construction Stage Based on Fuzzy Analytic Hierarchy Process

“…Major factors that increase the risk of accidents in tunnel portals may include the topography, geological and geotechnical properties of the rock mass and soil; rainfalls and underground waters; and construction methods. Since the influencing factors are diverse, complex and uncertain, which make the tunnels prone to slope instability, large deformation, tunnel collapse and others during the construction of tunnel portals, the lack of risk assessment and management may increase economic costs, prolong the time period allotted for a project and even cause fatal accidents [4]. Hence, risk assessment of tunnel portals during construction is necessary to manage and respond to the associated risks [5].…”