This paper introduces the importance and requirement of quality control during construction of a drilled shaft. The duty of the inspector and the elements to be included in a drilled shaft installation plan are introduced in detail first. What should be included in the construction record or document and in the quality control record are then listed in the paper. Subsequently, the construction quality control method, commonly used in the USA for post grouting drilled shafts, is briefly described. Possible defects resulting from bad quality control during construction of a drilled shaft are listed in a table for reference. Finally, how the concrete property affects the performance of a drilled shaft after the loading test is explained via two case examples.
According to the experiences of deep excavation engineering in recent years in Taiwan, and the progress of the numerical analysis software and the theory, the key to success in the deep excavation engineering is the retaining wall design and the quality of the construction. The most difficult part to control is the construction of the diaphragm wall which has been used widely in the retaining facilities of the deep excavation engineering. The main reason is that the width and the penetrate depth of the diaphragm wall should be decided in accord with the scale of excavation, the layers of soil, the condition of groundwater and the plan of excavation construction.
The variation of layers in the construction site should be grasped at all times to determine whether it would influence the construction or not. This observation should be carried out from the construction of the guide ditches to the treatment of the sealing by the experiences of the similar constructions or the existing local experiences.
Through the accomplishment of the first and the second stage of the Taipei MRT network, the later design or construction of the routes would usually cross the routes or the stations in operation; therefore, the excavation of the underground station is deeper and deeper, and the diaphragm wall becomes much thicker and deeper. Besides, the risk of the construction also becomes higher.
Since the key to success in deep excavation engineering is the design and construction of the diaphragm wall, this study details two cases about the design and the construction of the large scale diaphragm wall. One is the railroad switch of CK240 bid on the Taipei MRT Xinzhuang line, and the other is the diaphragm wall construction of CK240 bid on the Taipei MRT Dongmen station.
The National Freeway No. 1 Widening Project from Wugu to Yangmei (Wu-Yang Viaduct) provides an effective solution for the severe traffic jams in the northern Taiwan area. The project of 40km in length was accomplished after only 3.3-years. The lack of working space, while maintaining smooth freeway traffic nearby a geologically sensitive area and compact duration for construction, was a huge challenge in the implementation of this project. In the flat area, a shallow foundation was adopted first. Near the Wugu area, large-sized pile foundations were used on account of the deep bearing layers. From Linkou to Zhongli, the vertical shaft foundation is suitable for piers on the hilly terrain with less working space. This paper presents the decision-making process of the foundation arrangement, construction experience and overcoming of difficulties. It is expected the construction and quality management described in this article be used as a reference for similar construction works in the future.
The Dongao Tunnel is located at the section of Suao and Dongao on Highway No.9 of the Suhua Improvement Engineering Project. The Dongao Tunnel is about 3.3km long with a minimum overburden of 7m, in which the Suao Formation, South Suao Formation and Dongao schist are exposed from north to south respectively, and the Dongao schist is intercalated with marble and amphibolite. The lithology of the tunnel is mainly characterized by black schist and green schist nearby Southbound mileage 6k + 156.4, the bedrock which impacts the north-south traverse faults (Strike-Slip Fault) at the eastern side of the tunnel, as well as an interlayer shear zone between the different formations that caused the severe collapse during excavation. A support system was established and ground improvement was performed continuously during the excavation process. However, the complexity of the geology and geological conditions changed too fast and the scope of the weak zone extended some distance from the heading. This led to an expanded chimney type failure and there has no further excavation below the floor of the top heading. Therefore, some measures are used in this section by non-enlarging excavation type pipe roofing and steel grouting pipe, and grouting with a chemical grout (polyurethane resin) and cement grout, to backfill, consolidate and waterproof bedrock, to overcome the difficult geological conditions in the shortest time. The experience gained could be used in the design or construction of other similar tunneling projects with similar geological conditions.
Shield tunneling is made up of many construction tasks, such as constructing the shaft, executing grout for launching and arrival of shield tunneling, building a shield machine, producing lining segments, boring tunnels, performing backfill grout, excavating the cross passage, and other tasks. The design consideration and quality management of each work varies according to the various site conditions, external limits, and up-to-date shield tunneling technique for each case. Shield tunneling is in the high-risk construction category. The success of shield tunneling depends on the well controlled quality of each work. In this paper, the key points of quality management on shield tunneling for Taipei MRT are described. Then a shield tunneling case, focusing on the topic of design consideration, shield machine, tunnel excavation, and shield arrival, is introduced and studied. The experiences and the quality management in this case are provided as references for similar projects in the future.
Ground freezing is a soil improvement technique used in circumstances where soil needs to be stabilized so it will not collapse next to excavations, or to prevent water flow to ensure the construction safety. In this article, professional local construction teams perform successful shield tunnel launching, making connections and cross passage construction, sharing experience in the design approach, construction management, risk assessment and feedback analysis to establish the temperature management procedure. Risk identification was indicated and well controlled by mitigation measures. Several cases are introduced to show effective systematic management of ground freezing and these might be a helpful reference for similar applications.
The applicability of ground anchors to be used as permanent revetments has attracted much attention and review following the collapses of ground anchor slopes and serious casualties at the Lincoln Community, 1997 and National Freeway No.3, 2010. Many problems, such as corrosion of the tendon at the head and free section of the ground anchor as well as tendon break or fall off of the anchor head, have been found after years of use. In view of the above problems, it is wise to improve the safety and durability of ground anchors through design and construction improvements. Therefore, case studies on the Hsinchuang Depot of Taipei MRT and Wugu-Yangmei Section of National Freeway No. 1 Widening Project are included in the article. It is expected the slope ground anchor practices described in this article be used as a reference for ground anchor design, construction and quality management in the future. In the long run, engineers need to work together for introducing and developing new anchor materials and construction methods.
The lifecycle of slope monitoring covers design, installation, measurement and maintenance, whichever might affect monitoring quality. To ensure monitoring quality, it is necessary to perform good quality management throughout the full lifecycle. This paper first provides some basic understanding of slope monitoring, followed by a conceptual explanation of the quality management system of slope monitoring. Then important issues of quality management for the design, installation, measurement and maintenance are briefly discussed.
From the early 20th century until now, due to the sustainable development of soil mechanics and construction equipment, the construction quality control of embankment dam has been quite effective and strictly controlled. It has been modernized to cover at least two major items in foundation treatment and embankment filling. The construction quality control of embankment filling can be further divided into two major portions - construction materials and embankment compaction. This paper briefly describes the quality control of embankment filling, and introduces the construction quality control results of Hushan Reservoir, which was completed in 2014. The experience of Hushan Reservoir during construction is also summarized for reference.
Metallic materials are commonly used in geotechnical engineering; although, metallic materials would be affected by corrosion if they are submerged or come into contact with water, and this sometimes damages geotechnical structures. Glass Fiber Reinforced Plastics (GFRP) composite materials have the merits of light weight, high strength, and good durability. In this study, a three-point bending test was performed to obtain the rigidity and Young’s modulus; then the results of the experiment were used as feedback for the finite element analysis model. Analysis using finite element analysis software (PLAXIS 2D) for the safety factor was conducted to verify the feasibility of the GFRP sheet piles applied for reservoir basin revetment protection. The threaded surface of hollow GFRP threaded soil nail rods can increase the bonding strength between the rod surface and the bonding material. Pull-out tests were performed to measure the bonding strength between the threaded surface and the bonding material. Then a smaller GFRP rod coated with epoxy was inserted in a hollow, threaded rod so that splicing and pull-out tests were also performed to measure the bonding strength between the threaded surface and epoxy, and the required overlapping length was determined. The feasibility for implementation of the anchored sheet pile wall was assessed using the PLAXIS 2D finite element analysis software, including soil nail optimization analysis with the soil anchor length, height and angle as parameters, then the safety factor against soil slippage was evaluated. Finally, the PLAXIS 3D finite element analysis software was utilized to analyze the in-situ structure. Loading conditions corresponding to different slope angles, a pile system with uneven load distribution at the corners before the safety factor when the soil anchor is set on the corners were evaluated. Installation of the GFRP sheet piles in-situ was introduced at the end. This study indicates that the anchored GFRP sheet pile can be used in slope revetment.