Currently in Taiwan, the pipe jacking method is frequently used for construction, but only to the extent of straight line pipe jacking, while in Japan, curved pipe jacking method is often used. Besides being able to carry out straight line pipe jacking, curved pipe jacking method can also be applied to road type paths. This paper mainly introduces the curve line principles for curved pipe jacking method and points out the differences between the curved pipe jacking method and straight line pipe jacking method as well as the main considerations in making arrangements for the planning, design and construction stages of work. In addition, a comparison table of the “pipe diameter, pipe length and radius of turn curve” is provided for use during planning so as to be able to promptly assess the suitability of the curved pipe jacking method and determine the required pipe length and pipe material to be adopted for the curve section. Once the capabilities and limitations of the curved pipe jacking method are gradually understood, its deployment in the future will generally be widespread for underground utility works.
According to machine suppliers and contractors, the special cutter head should be used in pipe jacking in gravel or conglomerate formation, and the diameter of cutter head should be larger than 3 or 5 times of maximum grain size of the boulder. In Taiwan, the inside diameter of pipe jacking machine is usually less than 2.4 m in the current market while the boulder sizes are always larger than 1 m. I therefore the contractor and designer shall hesitate to use pipe jacking due to the decressed driving efficiency, or ground heave caused by huge size, high strength and hardness of boulder. In this paper, a studies of two cases pipe jacking technique used in gravel formation are presented. The possible problems and their solutions during construction are also discussed. Furthermore, the concept of particle configuration proposed by Walker is quoted to describe and clarify the fabric / structure of gravel formation. Finally, in order to aguire enough information when tunneling with pipe jacking, some work items are suggested while designers perform the site investigation.
Pipe jacking and microtunnelling is a technology for construction of pipelines to close tolerances for line and grade. Typically, these methods can be used for placing pipes ranging from 250mm to 3000mm in diameter. The operation process consists of pushing the tunnelling machine into the earth by means of hydraulic jacks carefully mounted and aligned in the jacking shaft. Typical placed rigid pipes include concrete pipe, vitrified clay pipe, and polyester resin concrete pipe. 300 mm and 400 mm PVCP and ABSP are also used for microtunnelling installation. Compressive strength, chemical resistance, hydraulic properties, abrasive resistance, durability, joint water tightness, workmanship, availability, and costs are the major consideration items in the design process. The test items of standard test method should include appearance, dimensions, straightness, roundness, compressive strength, chemical resistance, and joint water tightness. For flexible pipes, abrasive resistance and durability are also important test items. Pressure test and solvability test should be also checked for drinking water pipes.
The current construction method of cross passage for TMRT is grouting improvement of its site and surroundings with certain range. Afterwards, structure is excavated and constructed by tunnel excavation. Due to the underground pipes and the quality of grouting, that process of excavation had been seen seepage and sand loss usually made the construction of cross passage become the high risk work of civil engineering in TMRT. This paper presents two rectangle pipe jacking methods applied on cross passage and discusses technique and limit of pipe jacking methods for reference of future similar cases.
Pipe jacking is very sensitive to the geological conditions where it is applied on. Not only are geological survey and analysis needed during the design phase, but on-site experiences and auxiliary methods are also required during the construction phase to ensure a safe and successful completion.
Taking from the actual situations from TienMou, Taipei City, where sewage pipes are still under construction and andesine are the main composition of the geology, it is summarized that the sizes and strengths of the andesite, and the complex combinations of this once volcanism site are the three major factors for the application of pipe-jacking for the sewage. The related auxiliary methods that accompany jacking application to this site are also tabulated. It is our sincere hope that this preliminary article could serve as future reference for pipe-jacking planning, designs and constructions.
For tunnel construction work, sheet pile wall, solider pile wall, diaphragm wall, soil mixing wall and secant pile wall with bracing system are commonly adopted for the vertical shaft of pipe-jacking or shield tunnel. In additional, all-casing pile shaft is adopted for pipe-jacking having small diameter and steel lagging lining shaft is applied to tunneling in Taiwan. However, it is still difficult to apply these methods to a narrow jobsite in an urban area. Hence, shaft constructed by different caisson methods, which include self-weight caisson, pneumatic caisson and hydro pressure anchor caisson are introduced. An evaluation of the tunneling shaft constructed by caisson method is presented in this article.
In the 1999 Chi-Chi earthquake, unlike a common landslide a particular landslide occurring at Chiu-Fen-Erh-Shan was associated with contemporaneous formation of tektite induced by high frictional heat and large-scale eruptions of rock formations in the adjoining region. The occurrence of pseudotachylyte suggests a low water content in rocks and a high ratio of slip distance to slip-zone thickness so that high heat can be produced to initiate formation of glassy materials. Evidence for a large-scale rock eruption was observed in the nearby region of the landslide area. Three possible causes of rock eruption are proposed here including: (1) transmission of seismic waves gave rise to relative displacement and high frictional heating that caused vaporization of pore water in association with high seismic acceleration and created fractures and adjoining rock eruption; (2) propagation of seismic waves did not produced relative motion along fractures but built up pressure forcing eruption of pore fluid and rocks; (3) high frictional heat produced by the processes of large-scale landslide increased the temperature and pressure of pore water. The country rocks were uplifted and erupted when the uplift force exceeded the gravity and cementation forces during the period of strong seismic motion. Although all the aforementioned processes are possible causes of rock eruption in the study area, the mechanism and location of eruption as well as the landform features created by them are different. This study focuses on discussion of such differences.