Study On The Behavior Of Micropile For Transmission Tower In Soft Soil

Compared with common bored-piles, micropiles have merits of higher bearing capacity, less occupancy for construction, and greater adaptation to any type of soils. Instead of a reasonable calculation theory for micropiles, the design method for common large-diameter piles is mostly adopted, because little acquaintance is obtained about its construction technology, behavior and capability for its short application history in our country. For above reasons, it is necessary to study a number of full-scale field tests to make sure of a economical, safe construction technology of micropiles, and analysis the load-transfer rules and the deformation behaviors of single pile and pile grovip to provide bases for the design of micropiles in soft soil.In this paper, a scries of constructional process for micropiles is concluded through laboratory experiments and field construction. A full-scale field test is conducted to reveal the real behaviors of single pile and pile group of micropiles in soft soil. The test results indicate that they have a good ability to resist all kinds of loads. Based on an overlapped-form strain model of the soil surrounding a pile, which represents the load transfer mechanism, a theoretical solution for the deformation of a single pile under a given uplift load is developed using the compatibility condition of pile and the soil around it. The method takes into consideration tension deformation of pile and ultimate state of pile skin friction, which analysis the group efficiency and behaviors of double-pile and multi-pile group with the Mindiin's solution. The failure mechanism is also discussed about single pile and pile group under lateral loading.Moreover, p-y curve method is used to analysis the their behaviors, by which theresults are computed agree well with field tests. Based on the above analysis, calculation methods of plane and space pile structures are proposed.Finally, micropile is applied in an engineering foundation, and is conducted a series of field tests, which exhibits a good bearing capacity. As a consequence, it issure that micropile has a wide useful application in engeering.