A cut slope in Rajamandala, Indonesia exhibited unexpected large-scale deformation during the excavation process which was revealed by the clinometers attached to the preventive piles. A geological survey indicated that the mudstone layer composing the slope had been folded by tectonic movement and was highly weathered and eroded at the surface. The above internal factors could have resulted in the significant deformation of the slope, although few studies have focused on the influence of folded structures and horizontal in-situ stress on the deformation behavior of cut slopes. Therefore, the objective of this paper is to clarify the influence of the folded structure and anisotropic in-situ stress state induced by tectonic movement on the deformation behavior of the aforementioned cut slope. To achieve this clarification, numerical analyses were performed based on the explicit finite difference method included in the FLAC2D software using different geological structures and in-situ stress states. Consequently, it was revealed that such folded structures can lead to larger displacement in cut slopes when compressive stress concentration occurs at the bottom of the fold. Moreover, an anisotropic in-situ stress state can result in shear failure at the foot of the mudstone and reproduce the displacement of piles that possess shapes as close as possible to those observed at the site. These analytical results confirmed that the folded structure and anisotropic in-situ stress state were the inevitable factors in the large deformation of the cut slope in Rajamandala, Indonesia.
The subtle alteration of surface geometry from a fresh surface to a sheared surface usually results in a considerable variation in the shear strength of jointed rock mass. Through profiling surfaces of the granite joints before and after the shear tests, an evaluation scheme was newly proposed by determining a desirable characteristic index and sampling interval of surface measurement in order to distinguish fresh and sheared joint surfaces quantitatively. The measured data demonstrated that although the mean Z2 (root-mean square first derivation) values of all the profile lines were confirmed reasonable for estimating the joint roughness coefficient (JRC) value of the fresh joint surface, it could not completely evaluate the roughness of the sheared joint surfaces. Meanwhile, the distribution of slope angles, as the characteristic parameter, was proved to enable to clearly distinguish the fresh and sheared rock joint surfaces incorporating the small sampling scales (≤0.1 mm). The numerical simulations implemented in a mechanical shear model could confirm the critical effect of a slight change in surface geometry and further prove that the sampling interval of 0.1 mm could sufficiently capture the evolved waviness and unevenness of rock joint surfaces. Overall, it was confirmed that the results of our study provide new clues for evaluating the surface roughness of fresh and sheared rock joints and can be beneficial for understanding the variation of surface geometry during the shear process.
The hinge type of precast concrete arch culvert was introduced to Japan from France in the 1990s in consideration of the saving of labor, shortening of the construction period, and high quality control of the concrete members. However, due to the 2011 off the Pacific Coast of Tohoku Earthquake (March 11, 2011), the three-hinged precast arch culverts that had been constructed in Japan at the beginning of the period when precast arch culverts were firstly introduced, suffered damage, which spoiled their serviceability. According to the extent of the damage and the type of culverts that were damaged, the longitudinal structural connectivity of the culverts was assumed to be one of the possible reasons for the reported damage mechanism. Therefore, the objective of this paper was to clarify how strongly the longitudinal structural connectivity influenced the longitudinal seismic behavior of the three-hinged arch culverts. To achieve this objective, an elasto-plastic finite element analysis was conducted with an analytical model that could capture the characteristics of the damaged culverts. Simultaneously, a penalty method with the bi-linear spring model was applied as a solution to the contact-impact problems of the precast segmental arch members. As a result, it was found that the weaker longitudinal structural connectivity in the damaged culverts allowed the torsional displacements of the arch members to induce critical damage to the arch members, namely, edge defects in the arch crown and concrete foundation. The numerical results proved the unignorable influence of the longitudinal structural connection on the possible damage to three-hinged arch culverts.
Abstract In this study, a series of long‐term, intermittent permeability experiments utilizing Berea sandstone and Horonobe mudstone samples, with and without a single artificial fracture, is conducted for more than 1000 days to examine the evolution of rock permeability under relatively high‐temperature and confining pressure conditions. Effluent element concentrations are also measured throughout the experiments. Before and after flow‐through experiments, rock samples are prepared for X‐ray diffraction, X‐ray fluorescence, and scanning electron microscopy coupled with energy dispersive X‐ray spectroscopy to examine the mineralogical changes between pre and postexperimental samples, and also for microfocus X‐ray CT to evaluate the alteration of the microstructure. Although there are exceptions, the observed, qualitative evolution of permeability is found to be generally consistent in both the intact and the fractured rock samples—the permeability in the intact rock samples increases with time after experiencing no significant changes in permeability for the first several hundred days, while that in the fractured rock samples decreases with time. An evaluation of the Damkohler number and of the net dissolution, using the measured element concentrations, reveals that the increase in permeability can most likely be attributed to the relative dominance of the mineral dissolution in the pore spaces, while the decrease can most likely be attributed to the mineral dissolution/crushing at the propping asperities within the fracture. Taking supplemental observations by microfocus X‐ray CT and using the intact sandstone samples, a slight increase in relatively large pore spaces is seen. This supports the increase in permeability observed in the flow‐through experiments.
