Academic literature on the topic 'Underground tunnel'

Abstract The indirect boundary element method (IBEM) is adopted to solve the 2D scattering problem of circular underground lining tunnels near canyons and slopes to the P-wave. The numerical results show that the canyon and slope topography near the underground lining tunnel has an evident influence on the surface displacement. The horizontal displacement amplification reaches nearly two times. The presence of slopes has a shielding effect on the nearby underground tunnels. The stress concentration exists at the top and bottom of the arch of the lining tunnel. The dynamic interaction between the slope and the tunnel should be considered when building a tunnel close to the slope.

Andekaleka Hydroelectric Development, Republic of Malagasy (Madagascar), comprises an 8 m high intake dam, a 4 km long unlined power tunnel, a surge shaft, a concrete-lined penstock, four steel-lined branch penstocks, an underground powerhouse, and a 0.5 km long tailrace tunnel. The scheme develops a 235 m fall in the Vohitra River. Two 29 MW Francis turbines have been installed, with space left for two more identical units.This paper describes the geotechnical aspects of the underground design for the scheme. The predominant rock type is good quality granitic gneiss, which required minimal underground support and lining. Where the power tunnel 'daylights' and crosses the Sahantsiva River, steel and concrete lining and drainage tunnels have been provided.The length and design of the steel and concrete lining and the system of underground drainage are described along with the design and support for the powerhouse cavern and the support of the powerhouse crane beams on rock shoulders. Key words: tunnels, penstocks, underground powerhouse, underground drainage, underground support, tunnel lining, Madagascar.

The tunneling system has become an important part of the present infrastructure system in all over the world. Therefore, it has become important to ensure the safety of the tunnels against any type of man-made blasting activities or other accidental blasting occurrence. In order to evaluate the performance of the tunnels against blast loading, a detailed review is carried out. Based on the review in the last couple of decades, the various parameters such as tunnel lining materials, tunnel shapes, tunnel lining thickness, tunnel burial depth, charge weight and standoff distance are high influences on the performance of underground tunnels against blast loading. It was observed that the tunnel roof and the tunnel wall center are most vulnerable to the blast loads. Also, it was found that more of the tunnel lining thickness results in lesser deformation at the tunnel roof and the tunnel wall center. The increase in the burial depth of the tunnel would reduce the extent of damage to the tunnel caused by effects of surface blast loading. The stiffness and strength of the ground media may be enhanced against the effects of blast loading by grouting measures. The studies revealed that the lining materials possessing blast waves absorbing properties can be best suited to be used in tunnel linings. Further, it was observed that more damage was caused to the tunnels due to the magnitude of the charge weight. An increase in the blast load causes a significant increase in the fracture area, residual stress and lateral displacement caused to the tunnel by the action of blast load. The standoff distance of the blast load from the tunnel also plays a significant role in the damage of the tunnel. More is the distance between the charge and the tunnel, lesser damage caused to the tunnels. In addition to that, the lining thickness was predicted and the trend was calibrated and fitted logarithmically with the available results. Based on the observation from the literature, it is concluded that the use of a single lining material in the tunnel against blast loading was studied predominantly in the couple of decades. Further, the performance of the tunnels in combination of different tunnel lining materials against blast loading was found limited. The influence of barriers to save the underground tunnels against blast loading was found limited.

Earthquakes of large magnitudes cause fault ruptures propagation in soil layers and lead to interactions with subsurface and surface structures. The emergence of fault ruptures on or adjacent to the position of existing tunnels cause significant damage to the tunnels. The objective of this paper is to study the interaction of an embedded tunnel within a soil layer and the soil deformations imposed upon by normal faulting. A centrifuge modeling under 80-g acceleration was conducted to investigate the rupture propagation pattern for different relative tunnel positions. Compared with the free field condition, due to tunnel and normal fault rupture interactions, focused on soil relative density and tunnel rigidity in this research, found that they can dramatically modify the rupture path depending on the tunnel position relative to the fault tip. The tunnel diverts the rupture path to its sides. This study presents the normal fault-tunnel interaction with the tunnel axis parallel to the normal fault line, to examine the changes that take place in fault rupture plane locations, the vertical displacement of the ground surface with tunnel presence and the effect of tunnel rigidity and soil density on fault tunnel interaction.

Because of the special geological structure, folds are the main place where underground water gathers and moves. When we build roads or tunnels in folds of the western mountain areas, we should consider the effect of underground water on surrounding rocks and on stability of lining of a tunnel. The author explains in system the movement of underground water in anticlines, limbs and synclines, analyzes the physical, chemical and mechanic effects on rocks during its movement, then puts forward the reasonable advices in choosing the location where a tunnel should be built and specifies the stability of a tunnel. Also, in order to solve the water-gushing problem which may occur during the construction, the author brings forward some control measures for reference when selecting tunnel line and constructing.

Dynamic stress concentration in tunnels and underground structures during earthquakes often leads to serious structural damage. A series solution of wave equation for dynamic response of underground circular lining tunnels subjected to incident plane P waves is presented by Fourier-Bessel series expansion method in this paper. The deformation and stress fields of the whole medium of surrounding rock and tunnel were obtained by solving the equations of seismic wave propagation in an elastic half space. Based on the assumption of a large circular arc, a series of solutions for dynamic stress were deduced by using a wave function expansion approach for a circular lining tunnel in an elastic half space rock medium subjected to incident plane P waves. Then, the dynamic response of the circular lining tunnel was obtained by solving a series of algebraic equations after imposing its boundary conditions for displacement and stress of the circular lining tunnel. The effects of different factors on circular lining rock tunnels, including incident frequency, incident angle, buried depth, rock conditions, and lining stiffness, were derived and several application examples are presented. The results may provide a good reference for studies on the dynamic response and aseismic design of tunnels and underground structures.

Blasting has been widely used for economical and rapid rock excavation in civil and mining engineering. In order to study the influence of relative horizontal distance and relative vertical distance between two tunnels on the dynamical response of the two tunnels, 10 numerical simulation cases are done by LS-DYNA 3D models under surface explosion by controlling the clear distance and height difference of double-line tunnel, and the ALE multimaterial fluid structure coupling algorithm is applied to analyze the dynamic response characteristics of double-line tunnel under different conditions. The numerical results show that the dynamic response characteristics of the tunnel lining are affected by the change of the clear distance and height difference of the tunnel. With the increase of the height difference between adjacent tunnels, the peak value of vibration velocity at the top of the lining on the blast face increases, which is due to the upward elevation of the right tunnel, which is more conducive to the reflection and superposition of stress waves. When the height difference of tunnel is 4–6 m, the vibration velocity and displacement of monitoring point C on the back blasting side will change abruptly, and the variation range of vibration velocity is about 25%, while the variation range of displacement is about 60%.

Historical and archaeological evidence shows that ancient Hellenes had developed underground aqueducts since the prehistoric times. However, innovative methods of underground aqueducts were developed in Hellas mainly during the Archaic, Classical, Hellenistic, and Roman periods. Since the well-known tunnel at the island of Samos, Hellas, was designed and begun its construction (ca. 550 bc) by Eupalinos of Megara (the first civil engineer in history), several underground tunnels (with and without well-like vertical shafts) were implemented in the country. The goal of Eupalinos tunnel was to transfer water into the town from a spring. This tunnel, representing the peak of ancient hydraulic technology, was dug through limestone by two separate teams advancing in a straight line from both sides of the mountain. Delivering fresh water to growing populations has been an ongoing problem since ancient times. Several underground aqueduct paradigms (e.g. Peisistration in Athens, Polyrrhenia in Crete), some of which are in use even today, are presented and discussed. After late Roman times and the Adrianic aqueduct a gap of about 1,700 years in construction of such hydraulic works is noted. However, a remarkable development of tunneling in Hellas appeared during the last 50 years due to the ‘cosmogony’ of the construction of infrastructure projects using modern technology, e.g. Evinos-Mornos aqueduct with 15 tunnels of 71 km total length and the diversion tunnels in Sykia to the Thessaly plain and Messochora of the Acheloos River of 17.5 and 7.5 km length, respectively. Also, very recently three small conventional tunnels and one tunnel boring machine (TBM) were constructed in Aposelemis aqueducts used for water supply of Iraklion and Agios Nikolaos cities in Crete. As a consequence, significant design and construction experiences were gained. Overall, it seems that underground aqueducts of modern societies are not very different in principle from those during antiquity.

Bayueshan tunnel (BYS) is an important construction crossing over coal mine goaf. The underground mining subsidence has led the tunnel cracked seriously in three years after it was built. In order to evaluate the coal mine influence and future stability of the tunnels, probability integral method (PIM) was used to calculate the tunnel deformation. PIM is an experience function method based on random medium theory which is used widely in China. With the parameters analyzed, the tunnels’ subsidence was calculated. The results show that it can interpret the tunnel damage well, and the maximum normal strain positions fit the damaged tunnel positions well. It proved that PIM can be used to evaluate the tunnel’s radial deformation caused by underground coal excavation. In order to maintain tunnels to keep a long-term stability, the future deformation was calculated in case the coal excavation continues. It shows that the tunnel would be cracked again if the excavation continued. Other reasons such as the old goaf deformation and water and vehicle dynamic load are also important reasons for the tunnels’ deformation. In order to keep traffic safety, it needs to reinforce the cracked foundation under the tunnel. Then, grouting injection was proposed to reduce the old goaf deformation under the tunnels. If the fracture zone under the tunnels disturbed by the dynamic traffic load, the old goaf will face a risk of sudden collapse. So, to ensure the grouting effect, the grouting depth should be deeper than the sum of traffic load influence depth and height of coal mine caved fissure zone. The grouting scope should keep all the crack rock area under the tunnel from being disturbed by the dynamic traffic load. This design can reduce the sudden collapse risk of the goaf and reduces the vehicles’ load disturbance on the cracked rock. The researched technology provides an engineering guidance to tunnel subsidence calculation, stability evaluation, and maintenance in complex geological and engineering situations.

This paper presents the issues of technical state of subsurface structures in operation and the erection of buildings under available development. It is stated that detailed monitoring of technical state of underground tunnels is essential, since the structure is unique and technologically complex. The aspects of geotechnical monitoring of underground tunnels are considered. The principles of geodesic monitoring of underground rings, tension increase in tube lining and pressure from the building under construction on the ground are described. Recommendations for underground tunnel monitoring are presented.