区分
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甲
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氏 名
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Saeid KHAZAEI
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| 論
文題名 |
STUDY ON EFFECT OF OVER CUTTING
AREA ON JACKING LOAD IN SLURRY PIPE JACKING METHOD |
| （泥濃式推進工法における掘削余掘部の推進力への影響に関する研究） |
| Pipe jacking is a
technique used to install an underground pipeline through a bore
created by a shield type drivage machine from a starting pit. Methods
of excavation range from hand digging to use slurry machines or earth
pressure balance machines (EPB) in different ground conditions. Slurry
pipe jacking system is particularly suited to both cohesive and sandy
soil. It can be used to construct pipe tunnels up to 3,000 mm in
diameter. During the pushing processes, mud slurry is injected into the
face and over cutting area, which is between the pipes and the soil.
The slurry fills the soil voids then the soil stabilizes due to the
slurry pressure. The thesis consists of 6 chapters. Chapter 1 presents the aims and the objectives of the research, while the last Chapter 6 outlines the main methodological and applied results. Chapter 2: This chapter studies thrust in slurry pipe jacking method. At first, effective parameters in thrust in pipe jacking operation are considered. For this aim, skilled theoretical and semi-theoretical methods of thrust prediction are discussed. From this part, it could be concluded that it is hard and impossible to insert analytically all of the effective parameters in thrust analysis. In this case, it needs a new conception of thrust analysis with care about impressive parameters in analysis in order to reach a clear thrust equation in the case of using slurry pipe jacking method. Chapter 3: This chapter is about workability of the new method of thrust estimation in slurry pipe jacking operation. The new method was checked and controlled by field data as well as the previous methods to clear its effectiveness. Case study for the new thrust prediction method in straight and curved area was considered and discussed. The results show that the predicted thrust with the new method is better harmony with real data. This chapter also considered thrust in large diameter slurry pipe jacking with permanent lubrication system in the largest slurry machine operation in Fujisawa city, Japan. The experimental method of Japan Sewage Association (JSA) was used to predict the thrust at the Fujisawa project. Comparison between thrust predictions by JSA and the new method show that the predicted thrust by the new method is in better harmony with the real thrust in this project. From the results of thrust in curved jacking area by Shimada et al. method, it could be understood the thrust is predicted acceptable by using this method. In the new method for curved jacking, it tries to state the pipe situation as a real state in operation. The results show that there are some differences between the thrust from field data and the calculated one. As a conclusion for comparison between the new method and Shimada et al. method, it can be mentioned that there is not a great difference between both methods. Chapter 4: This chapter presents a study on thrust and effect of permanent lubrication system on thrust. For this aim, some laboratory tests were conducted during a case study at Fujisawa city, Japan. From the lubricant compressive strength test, the strength and module of elasticity of lubricant material under different conditions were investigated. From these tests, it is clear that increasing in percent of mud slurry in mixture with lubricant reduces strength parameters of lubricant and low permeable lubricant gives higher strength parameters. In the last case, lower thrust in slurry pipe jacking method is predictable. From the test of dynamic friction for interface, the dynamic frictional resistance of concrete surface in contact with the lubricant material in different qualities of lubricant was investigated. It can be understood that the minimum dynamic friction happens in interface between the lubricant and the concrete. In direct shear box test, firstly test for the friction resistance of pure lubricant on concrete sample and secondly for real mixed sandy soil-lubricant sample on concrete were performed. In the first state, all of the samples were sheared through the lubricant material under different normal stresses. It can be inferred here that this state was related to roughness of concrete surface and cohesion for interface that was greater than that of the lubricant material. In this case, the cohesion and friction angle for the sheared surface were concluded 2.66 kPa and 9.89 degrees, respectively from Mohr-Coulomb criteria. In the second state of the test, the behavior of sample was similar to the saturated sand. In this case, the stable shear strength was not concluded for all of the tests. Shear strength and friction angle for the state of sandy soil from this test were suggested between 4-5 kPa and zero, respectively. Chapter 5: This chapter studies the over cutting area condition and the effect of lubrication in slurry pipe jacking method. Results show that it is impossible to have a clear understanding of the kinds of filling and void thickness using only the RADAR system. Finally, from the test conditions in this part, it is understood that the different conditions of targets on the back of the pipes are detectable globally by a RADAR device, and the effects of concrete pipe reinforcement cannot avoid getting acceptable results. According to investigation with a borehole camera, the void thickness was larger near the starting shaft than in other places. One reason for this is because machine slacking was great in this area. As time progressed, the void thickness became smaller because of the convergence of surrounding soil. The void situation may differ greatly from the position of sampling. However, it was confirmed that the lubricant existed in the voids of all sampling locations. Permanent lubrication systems such as DKI and TRS are used for reducing thrust at long distances. The idea of a relationship between the over cutting area and the needed thrust in slurry pipe jacking has been confirmed by comparison between the thrust data and the void thickness during the jacking process. This theory was proven in different locations of jacking operation. Also successful filling for the over cutting area for these systems was proved during the case studies. |
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