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As a countermeasure to the damage of spillways during earthquake, in this paper, the new lightweight method to fix the spillway on the small earth dam with geogrid was proposed. The series of shaking table tests were conducted at National Institute for Rural Engineering in Japan to discuss the superiority of the new method during shaking and the interaction between the spillway and small earth dam. As the results, it was confirmed that the superiority of the model with geogrids to the model without geogrid. Moreover, the spillway model showed detachment without geogrid from the dam body. Lastly, the mechanisms of the results were discussed to clarify the effectiveness of proposed method. INTRODUCTION Japan has over 20 thousand small earth dam to obtain water for irrigation. There is a spillway that is drainage facility to discharge overflowed water safely to downstream during floods. In general, spillways of the small earth dams are reinforced concrete although the embankments are made of soil. Therefore, in earthquakes, it is pointed out that the spillways detachment from embankments was observed by the difference of inertia or eigen frequency. Picture 1 shows the typical damage by the detachment between the concrete type spillway and embankment during Hyogoken-Nanbu earthquake in 1995. The detachment triggers not only water infiltration into the dam embankment but also secondary damage to downstream area of small earth dams. In order to prevent the detachment, the researches on the safety of the earth dam are required. Previous work on the behavior of geogrid-reinforced construction during earthquake is discussed. Watanabe et al. (2002) proposed a new aseismic type bridge abutment with geogrid-reinforced cement treated backfill. Koseki et al. (2002) performed comparison of model shaking test results on reinforced-soil and gravity type retaining wall. Bathurst et al. (2002) conducted to assess the seismic performance of reinforced soil walls.
The thrust force generated by internal water pressure tends to move bends of underground pipelines to back side. Commonly concrete blocks are set up on the bends in order to resist the thrust force. However, such heavy concrete blocks become a weak point during earthquake. Therefore a lightweight thrust restraint with geosynthetics and anchor plate is suggested in this study. In previous study the lateral loading tests were carried out to investigate the effect of the proposed method. In addition the resistance mechanism of the proposed method has investigated by numerical analysis. In this paper in order to establish the detail design for the new method, the lateral resistance due to proposed method is estimated. In addition, in order to compare the experimental value, model tests are carried out. As the results, estimation by proposed model was good agreement with experimental results. INTRODUCTION On bends of pressure pipelines for transporting water, gas and oil, unbalanced force is generated. Generally this force is called thrust force. Commonly concrete blocks are installed on the pipeline bends. However, in the Hokkaido-Nansei-Oki Earthquake in Japan in 1993, it was reported that bends having concrete blocks caused the damage of pipelines since such heavy concrete blocks were moved largely due to inertia (Mohri et al., 1995). For these problems, Kawabata et al. (2004) proposed a lightweight thrust restraint using geosynthetics and anchor plate as shown in Fig. 1. In case of using the proposed method, lateral resistance increase due to the side friction of geosynthetics-ground and passive resistance acting on the anchor plate. In previous study, lateral loading tests using model pipe (φ90) was conducted and it was clear that the new method was extremely effect to provide lateral resistance (Kawabata et al., 2006).
Large Scale Tests of Buried Bend With Lightweight Thrust Restraint Using Geosynthetics
Kawabata, Toshinori (Kobe University) | Sawada, Yutaka (Kobe University) | Ogushi, Ken (Kobe University) | Totsugi, Atushi (Taisei Kiko Co., LTD) | Hironaka, Junichi (Mitsui Chemicals Industrial Products, LTD) | Uchida, Kazunori (Kobe University)
The thrust force generated by internal pressure tends to move the bend of underground pipeline to back side. Commonly concrete blocks are set up on the bend in order to resist the thrust force. However, such heavy concrete blocks become a weak point during earthquake. Therefore a lightweight thrust restraint using geosynthetics and anchor plate was suggested in this study. In previous study the lateral loading tests were carried out to prove the effect of the proposed method. In this study, large scale tests were conducted using a pipeline (φ300) to investigate the effect of the proposed method in actual size. As the results, the resistance force in case of using proposed method increased 60% comparing in case of non-reinforced pipe. In addition it was clarified that the incremental resistance due to proposed method was influenced by the stiffness and the length of geosynthetics. INTRODUCTION In bends of buried pipelines subjected to internal pressure, for example pipelines for water, gas, oil and so on, unbalanced force is generated depending on the pressure level and the bending angle. Generally this unbalanced force is known as thrust force. Commonly thrust force is supported by the passive earth pressure acting on the bends. In case that thrust force is larger than the estimated passive earth pressure, concrete blocks are set up on bends. Large-scale test for pipe bend was carried out using pipelines (φ 500) (Mohri et al., 1996). In that study, it was found that concrete blocks were effective for thrust force and lateral resistance of bends increased in case of using crash gravel as backfill materials. However it was reported that thrust blocks on bends caused damage of pipelines during earthquake since they were moved largely due to inertia (Mohri et al., 1995). In addition, it can be expected that differential settlement occurs in case of using such heavy concrete blocks on soft ground.
The purpose of this research is to clarify the evaluation of the bearing capacity of a pile with multi-stepped two diameters. Model tests were conducted by driving multi-stepped type metallic piles into two kinds of dry ground to evaluate the bearing mechanism. As the result of experiment, the following points about the pile with multi-stepped two diameters were confirmed;for the bearing capacity of convex part with the long concave part, the decrease is small after the peak, and for decomposed granite soil, the peak of the bearing capacity of convex part was not observed. Quantitatively, a procedure used the spherical cavity expansion method offers potential for better prediction on the bearing capacity of convex part with the long concave part. Another procedure could be good predictions for the bearing capacity of convex part with the short concave part, considered the bearing effect on the base of the convex part. INTRODUCTION A pile with multi-stepped two diameters (abbr. as MS-pile) is constructed by using the boring rod with multiple swing blades. The rod mixes the in-situ soil and the cement and produces the cylinder of convex and concave parts along depth alternately. The pile takes into account the environment concern, which means that it has the characteristics to reduce not only construction time and cost, but also construction noise and waste soil. MS-pile as well as nodular pile, which is often used in Japan, is a kind of friction pile. However the bearing mechanism would be different due to difference of the shape between two piles. The study of the nodular cylinder pile that has umbo in its own has developed since the early 1980's. Yamagata et al. (1982a, 1982b) verified the frictional resistance of the nodular pile form the model test, and the data of the field vertical tests statistically.
- Construction & Engineering (0.34)
- Energy > Oil & Gas > Upstream (0.31)