Shield tunnels are usually adopted in the MRT system and are constructed right in the alluvial soil layer of Taipei metropolitan area. The main problem for buildings adjacent to the tunnels is the control of the lateral displacement during the basement excavation of buildings. In some special cases, the MRT shield tunnels are constructed under buildings, in which, the difficulties in the design and construction of building need to be solved. This paper introduces a case where two shield tunnels existed under a to-be-built building. In this case, piles were applied between the two tunnels. A test pile program was carried out in the initial stage of construction, and the monitoring instrument was installed to monitor the response of the soil layers during the pile construction. Based on the measured data, piling procedure was revised to avoid influences to the soil layers. In excavation and structure construction, subsequent to the piling works, the shield tunnels were also closely monitored and measures were taken according to monitoring data, as to minimize the influence of building construction to the functioning MRT.
The Honduras El Cajón dam, with a height of 226m, is a world famous high arch dam. Its foundation sits on the Karst Limestone bypassing four high-dip-angle faults. The unique ”bathtub” type curtain grouting layout of the reservoir stretches from the Limestone to the upstream Igneous rock, occupying a total area of 530,000 m2. Both the uplifting water pressure and seepage quantity acting on the dam foundation have been increased abruptly since 1985, when the reservoir project was completed and in service to retain water. Since then, the grouting works to repair the curtain have been conducted for three times. The first and second works were completed in 1985 and 1995, respectively, while the third work, known as the MOS repair project, was proceeded between 2014 and 2017. Specifically, the third grouting work focused on the N45°E fault, big fissure, large water head condition, and huge groundwater inflow in the Karst Limestone. The seepage quantity in the dam foundation was successfully reduced at the end.
Geological investigation plays a crucial role in zone planning and assessment of slope stability. In general, the layout of geotechnical monitoring instrument and geotechnical analyses all rely on the results of geological investigation. The mechanism of slope failure and the related parameters are also based on the geological investigation results. Moreover, the investigation results can also be used to set up the schemes for regional disaster prevention and mitigation. As an example, the Jiufen geological survey showed that the terrain sloping toward east or northeast in the north of Ruifang fault are mostly oblique slopes or partial dip slopes. However, there is no slope daylight so the dip slopes generally remain stable. For unstable slopes, the inclinometer readings revealed that the sliding surface is located at the interface between the colluvium and sand/shale layer and its movement is governed by the fluctuation of groundwater. In the south of Ruifang fault, there is a thicker layer of colluvium. In case of a landslide, it should be a circular sliding within the thick colluvium.
Based on traditional experience, the stabilization procedure for landslide disasters often focuses on the effectiveness of restraint works, in which, the reinforced concrete and the eco-landscape could often be overused and ignored, respectively. Environmental-friendly constructions, considering the importance of the ecology, have now become a key issue in the engineering world. This paper reveals a case study that integrated the above-mentioned concept and demonstrates the rectification effect of the stabilization procedure based on the landslide of the tennis court in Taipei National University of the Arts occurred on September 29, 1991. This case study may serve as a reference for the stabilization procedure deliberating upon the concept of safety and eco-landscape.
Attributed to the rainstorms and the Typhoon Toraji in 2000 and 2001, respectively, many debris flows were induced in the Kukuan area along the Tachia River. The riverbed elevation first accumulated to a height of 10m, and then 9m by the fallen rock and soil at the tailrace outlet of the Kukuan Branch Plant of the Tachia River Powerplant. Subjected to the Typhoon Mindulle in 2004, the elevation of the riverbed once again reached 10m, which is almost the same elevation as to the Access Tunnel of the Plant. The river water overflew the entrance of the underground powerhouse and flooded the powerplant. This paper, under the particular geological and hydrological environment, addressed many watertight and stabilization treatments practiced from 2003 to 2007, for large cavern and tunnels. Those treatments included curtain grouting, watertight grouting, consolidation grouting, drainage gallery and many other stabilization treatments.
In 2009, the No.20 Highway among Qinhe, Fuxing Villages in Taoyuan District, Kaohsiung was severely damaged by the heavy rainfall of 2,578 mm brought by the typhoon Morakot, which resulted in a debris deposition of more than 30-40m thickness in the Lao Nong River. The roads and bridges along the river were completely buried under the riverbed. The hydrological geology was so unstable that the rehabilitation should take considerations into preventing complex disasters, including landslide, deposit, flood and debris flow. Through the previous assessment of the talus in the site and the long-term stability of the riverbed, the target of repair is the so-called “mid-term” highways, that have served for 10~15 years. The most complicated design and construction conditions encountered in the Mingba-Kelu Bridge was the critical path for the site access of construction. Some design changes had to be carried out because of serve variety of the environment, especially around the Mingba-Kelu Bridge area. The rehabilitation was successfully completed and would serve as a base for the new hope to reopen the Southern Cross-Island Provincial Highway.
In compliance to the energy policy of Taiwan, Taichung LNG Receiving Terminal Phase II Investigation project is currently under construction; the construction includes above-ground storage tanks, a gasification facility at the terminal itself, a 26-inch gas pipeline, and a switching station. The 26-inch gas pipeline work, consists of approximately 18.2 km, was installed by conventional techniques: i.e. including four sections which installed via Horizontal Directional Drilling (HDD) method are performed.
The article discusses the basic design principal and equipment for the HDD, the construction process of the four HDD sections, and the contingency solutions, i.e. the HDD construction planning for the long-distance pipeline, the settlement monitoring crossing under roads, the bit balling phenomenon encountered in mudstone, an auxiliary method with casing and auger in cobble layer, and the pilot drilling in the directions technique. It is hoped that the paper can serve as a reference for future HDD projects.
The construction of Tender C2, a 4.7 km tunnel that connects Pingtung County and Taitung County, is a critical path for the Widening and Improvement Project of South-Link (No. 9) Highway. Groundwater gushed out from the north entrance of the tunnel in the southbound lane while undergoing the 688th round of excavation led to the suspension of the tunnel construction. The water surged with a maximum and an average rates of 27 ton/min and 20 ton/min for 30 days, respectively. The authority immediately coped with the emergency drainage and reinforcement measures to avoid groundwater inrush-induced catastrophic collapse from the excavating face, and supplementary geological explorations were carried out. Following the geological conceptual models, the drainage and grouting improvement measures were carried out to overcome the suspension of the tunnel construction. The manuscript introduces the background of the tunnel project and the process of water inrush, and summarizes the results of the supplementary geological explorations, and puts forward suggestions on the construction of tunnels in the Chaozhou Formation.
At first, the paper reviewed international and domestic excavation case studies involving huge underground caverns. Subsequently, based on the Zengwen desilting tunnel and subjected to the lateral pressure and shallow cover, the consideration to change from a single large-span cavern to a double cavern was addressed, as to mitigate the influence of the lateral pressure. At last, the results of the supplementary survey, analysis, and countermeasures for the support adjustment in the rock pillar between the two caverns are explained. Also, the effectiveness of ground LiDAR technology applied in this project is described.
This article discusses The Rapid Transit System of Taichung City at the CJ920 Section, considered as the first project adopting a large-scale well foundation method in Taiwan. The project focused on the densely population and limited space of the metropolitan environment conditions. The well foundation built on gravel layer of the central Taichung area was also developed to scrutinize safety improvement on the traditional well foundation method and environment pollution prevention. The well foundation method applied on fine gravel layer sites could reduce acoustic noise, dust pollution and increase construction safety. Therefore, this method could be widely used in the metropolitan area by the civil and public projects.