The Yangtze River Large-span UHV Pile Soil Deformation Coordination Mechanism And Its Applied Research

Foundation stability refers to the building loads,the foundation soil can remain stable.If the foundation stability can not meet the requirements,the foundation under the loads of structures will generate partial or whole shear failure,the damage will affect the safety of structures with normal use.The pile foundation for the long-span UHV power transmission tower across the Yangtze River is difficult to construct.And the settlement control during construction is extremely strict,especially for the special geological environment associated with fluvial facies.Therefore,it is very significant to study the factors that are known to affect the construction of the pile foundation for the long-span UHV power transmission tower in the vicinity of the Yangtze River where the topography is very complex.In this paper,the concept of deformation compatibility between pile and soil is introduced to a real engineering application entitled “Pile foundation engineering for the Lingzhou-Shaoxing ±800 kV long-span UHV power transmission tower across the Yangtze River” in an effort to investigate the deformation compatibility mechanism between soil and the considered pile as well as to optimize the pile foundation.The main conclusions emerged from this study are summarized as follows.? The original designed pile foundation cannot meet the requirement of the external load of approximately 300 t.The construction of this pile foundation is very likely to encounter risks such as towel incline,excess settlement,and failure in stability.Consequently,the designed pile foundation need to be reinforced.? The coordinated failure of the pile-soil system is progressive with the application of the external load.In the early stages of the external load application,the pile is penetrated into the soil.With increasing further the external load,the failure is extended to be damage of the shallow soil and the foundation structure,and then to be settlement of the entire cushion cap,damage of the cushion,and heave of the surrounding soil.Finally,local instability failure occurs due to incapability of the pile foundation to support the excess external load.? A new reinforcing scheme that combines cushion reinforcement with soil grouting is proposed to strengthen the pile foundation.This strengthening approach improve dramatically the bearing capacity of the pile foundation,leading to the satisfaction of the construction requirements.? Under the effect of the vertical external load applied on pile tip,the pile,the soil,and the cushion respond jointly and deform in a coordinated manner.? Some valuable suggestions for the real engineering application are proposed according to the conclusions derived from numerical simulation and field monitoring.