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Re: Raymond Step Tapered Piles[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: Raymond Step Tapered Piles
- From: GSKWY(--nospam--at)aol.com
- Date: Tue, 9 Dec 2003 08:13:34 EST
If you do a google search, you will come up with a lot of hits. The below was copied from a geotech site in Europe.
The Raymond pile, invented in 1897, is one of the oldest pile types, but is still used in several countries, especially North America. The Raymond pile is also known as the "Step-taper pile", due to the special steel shell and the typical mandrel. Step-tapered piles are formed from 1.2, 2.4, and 4.9 m straight-sided, thin-walled segments of spirally corrugated steel.
Each successive pile element decreases over a length of 2.44 m by 25 mm in diameter. The minimum diameter (at the pile toe) is 0,212 m. Step-tapered piles can be driven to a maximum depth of about 40 m. The 40 m long pile has a tip diameter of 0,212 m and a shaft diameter (at the ground surface) of 0,438 m.
The pile is installed using a unique driving process. A specially shaped mandrel is inserted into a thin-walled pile tube and the driving force is transmitted along the casing and to the bottom of the pile. In this way, the wall thickness of the pile tube can be kept to a minimum.
The installation procedure of a Raymond pile is as follows:
The steel shells are assembled before driving to the required length.
The tapered steel mandrel is inserted into the pile tube and expanded to grip the shells.
The mandrel and shells are lifted into the leaders of a pile rig.
The shells are driven to the required level by a single- or double-acting hammer.
The mandrel is contracted and withdrawn.
The interior of the pile can be inspected.
The shell is concreted with or without a reinforcing cage. After pile installation, the casing of a Raymond pile is watertight, as the shells are screwed together and sealed. Also the alignment of the shells can be inspected before the concrete is cast. The shells provide protection in squeezing ground or against failure of the shaft in tension due to ground heave when piles are driven in large groups.
Raymond piles have a high bearing capacity, because of the corrugated surface of the pile shaft and their conical pile shape. They are suitable for high pile loads and difficult driving conditions.
Raymond piles have been used successfully in many parts of the world. They are adaptable to varying soil conditions since sections can be added or taken away as required, to suit varying depths of penetration. When excessive pile lengths are required, the lower section can consist of a steel pipe or a concrete section. Steel pipe step-taper piles have been driven to a depth of 75 m.
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