DX挤扩灌注桩技术在铁路桥梁工程中的应用

The application of DX rotary and squeezed pile on railway bridge engineering

DX桩是近年来新兴的一种变截面新桩型。是在钻孔灌注桩的基础上，使用专用挤扩设备在桩底和桩身挤扩成为支盘状，然后浇灌混凝土后形成的桩身、分承力盘和桩根共同承载的桩型。DX桩可较大幅度提高单桩承载力。试验表明单桩承载力比同等条件下的直孔灌注桩提高80％以上。DX桩可在粘性土、粉土、砂土层、强风化岩、残积土中挤扩承力盘，也可在卵砾石层的上层面挤扩成盘，更适宜在粘性土、粉土或砂土交互分层的地基中使用。DX桩的桩身直径可为400—2000mm，桩长可达60多米。是一种值得推广应用的新桩型，已在高层建筑、公路桥梁、一般工业与民用建筑及高耸构筑物桩基工程中得到广泛应用。在铁路桥梁的桩基础建设中若推广使用DX桩，可充分发挥其承载力高和沉降小的优点，能减小桩身截面和长度，这将有效缩短工期，降低工程造价，带来不可估量的经济效益和社会效益。

Squeezed pile with plates （being DX pile） is a new type pile that has been developed in recent years. Based on common cast - in - place pile, it adequately avails itself of the bearing capacity of each soil hard layer. According to the difference of design bearing capacity and engineering geological condition, it consists of plates by the squeezing equipment of hydraulic pressure in the different parts of DX pile. DX pile is a sort of change - section pile and is priority to shaft resistance between friction pile and shaft pile. Making use of the tip re- sistance of breaches and plates and shaft resistance around the branches is in order to add the shaft resistance and tip resistance. In situ test has shown that it can sharply improve the bearing capacity of pile. DX squeezed pile can- not only be applied in clay, silt, sand, weathering rock mass and residual deposits of soil, but also can be used in interactive layers of gravel, clay, and sand. The diameter of DX squeezed pile can be 400 ~ 2 000 mm, and the length of it can be more than 60 m. It is a new type of pile which has a bright future for application. Now it has got the extensive application in high building, bridge, civil engineering and high structure. Due to it＇ s good bearing capacity and low settlements, it can an be applied and promoted to different foundation engineering of railway bridge engineering, and would get a good prospect of application and extension .