Experimental Investigation on Flexural Behaviors in Framed Structure of PST Method
Existing underground pipe jacking methods use a reinforcing rod in a steel tube to obtain structural stiffness. However, some problems such as inconvenience of works and expensive materials resulted from limited working space and reinforcing works are existed. To resolve these problems, a new pipe jacking method, namely PST (Prestressed Segment Tunnel) method, was developed which used joint to connect the steel segment and form erection structure. For evaluating the flexural capacity of the PST method structure, a experimental test was conducted. The parameters considered in the test were span-to-depth ratio of segment, diameter of steel tube at the corner, prestressing force, and welding of joint. The flexural behaviours with the effect of load capacity in serviceability state according to different parameters were examined.. The frame with long segments could increase flexural stiffness and the specimen with large diameter of concave corner showed excellent resistance ability to the negative moment. In addition, welding of joints increased the flexural capacity. Keywords—PST method, Pipe jacking method, Flexural behavior, Prestressed concrete.
TBM vs. MTBM: Geotechnical Considerations
Microtunneling machines (MTBMs) were first used for pipe jacking projects in the San Francisco Bay area in the early 1990s. As the vast majority of MTBM pipe jacking projects have been successfully completed, it has become the expectation of both owners and communities served that microtunneling is the practice of choice in trenchless technology. This paper discusses man-entry tunnel boring machines (TBM) and MTBMs in relation to geotechnical conditions that should be considered when choosing the method of tunneling. The paper provides a comparison of the capabilities and limitations for the machines relative to soil, bedrock and groundwater conditions as well as changes in subsurface conditions within an individual tunnel drive.
SOIL IMPROVEMENT AND REINFORCEMENT
This paper presents a state of the art review relating to four topics selected because of their interest and new technical aspects: densification of granular soils; grouting in the area of soil improvement; reinforced soil retaining structures; and use of soil nailing in tunneling in the area of soil reinforcement.