A pile with multi-stepped two diameters (MS-pile) is applied for the foundation of medium scale structures. A series of model pile tests subjected lateral loads is conducted to discuss the following issues;

  1. bearing capacity of piles with multiple-stepped two diameters compared to the one of cylinder pile,

  2. ground displacement behavior around lateral loaded pile,

  3. bearing effect due to the shape of convex and concave,

  4. earth pressure distribution along the piles.


The purpose of this study is to clarify the bearing mechanism of laterally loaded piles as shown in Fig.1 (a) and (b). The pile is frequently subjected to the lateral load caused by wind and earthquake. The loading test is important for pile foundation to evaluate the quality and the credibility.

In the past lateral loading tests, full-scale tests were conducted by Feagin (1937). Using this result, Chang (1937) proposed the linearity behavior of pile derived from of the soil resistance and pile deflection. The non-linearity of the soil resistance and pile deflection was first developed by McClelland et al. (1958).

Recently, the ultimate state design concept is needed to quantify the seismic load and displacement at the limit-state. Wakai et al. (1995, 1998) investigated the load zone beyond linear elastic zone. In addition, seismic load and displacement increased since the 1995 Hyogoken- Nanbu Earthquake. Koda et al. (1999, 2001) examined the behavior characteristic of pile with the centrifuge model test. Prasad et al. (1999) clarified lateral earth pressure distribution along rigid model pile, and this distribution was compared with earlier ones of Broms (1964) and Meyerhof et al. (1981).

On the other hand, the nodular cylinder pile as shown in Fig.1 (c) has been developed since the early 1980's. This shape is similar to the one of MS-pile.

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