| Micropiles are defined as small diameter, drilled, cast-in-place, lightly reinforced grouted piles. The main characteristic of a micropile is its small boring diameter, which allows its construction in almost any ground condition with equipment smaller than those used for traditional piles. Micropiles were first installed in Italy in the 1950s and were conceived as a method to underpin historic buildings and monuments. In the 1970s, this new technique was introduced in the U.S. Micropiles can be used under restricted access conditions, and they can provide not only an excellent structural support but also a system that minimizes settlements.Chapter 2 is a literature review of micropiles and compaction grouting, including descriptions of the different types of micropiles and methods of design. Chapter 3 based on the elastic theory, the stress between the pile and the soil is assumed to be a function of the relativedisplacement. It can take the plastic behavior of the soil around the pile into account, and also can analyze the battered pile and pile group. ANSYS computing show that the bearing capacity of the micropiles depend on the load inclination and the micropiles battered angle. Under the vertical load, the vertical micropiles has bigger bearing capacity than the battered micropiles. Under the lateral load, the positive battered micropiles has bigger bearing capacity than vertical and the negative micropiles. The allowable settlement of the micropiles head is suggested and the vertical pile can bear loadwith inclination of less than 10°, and the battered micropile bearing vertical load can be angle of less 10°.The chapter 4 indicates the application of micropile in construction of bridge.It includes the following four parts: use directly as a basic of the bridge, applicate to underpine the bridge foundation, and in the vehicle bump approaching bridge parts.It has been proved practically that micropile had a promising application in bridge construction...
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