Composite foundation for collapsible loess region and construction method

Abstract

The invention discloses a composite foundation for a collapsible loess region and a construction method. The composite foundation for the collapsible loess region comprises a slab foundation and screwanchors buried underground, wherein the slab foundation comprises a main column, a step and a bottom plate arranged sequentially in the vertical direction; the screw anchors are vertically arranged and connected with the slab foundation; multiple concrete piles are connected onto the bottom surface of the bottom plate and are vertically arranged along a bottom surface edge of the bottom plate; one ends of the concrete piles are connected with the bottom plate; the other ends of the concrete piles downwards extend into a soil body; and the concrete piles are matched with the screw anchors through resistance so as to constrain the offset settlement of the slab foundation. Under the slab foundation, the concrete piles are arranged on four corners of the bottom plate, and the concrete pile foundations and non-collapsible soil under collapsible loess form frictional resistance so as to apply a constraining force to the circumference of the slab foundation, so that the effects on maintaining the overall foundation stability and preventing the foundation from being subjected to offset settlement after the soil body on the upper part touches water are achieved, and the composite foundation is ensured to be stably used at the collapsible loess region.

Description

technical field [0001] The application relates to the field of power transmission facilities, in particular to a composite foundation and a construction method for collapsible loess areas. Background technique [0002] The foundation is an important part of the transmission line. Ensuring its construction safety, reducing construction costs, shortening the construction period, and increasing its economy are the inevitable trends in the development of transmission lines; comprehensively consider economics, safety, environmental protection and water conservation issues, and construction schedules. It is of great significance to choose the appropriate basic type under different conditions. There are a large number of collapsible loess areas in Gansu and Ningxia in my country. This kind of soil is prone to subsidence when it encounters water, and the side friction parameters are significantly reduced, which seriously threatens the safety of the foundation of the transmission tow...

AI Technical Summary

Problems solved by technology

There are a large number of collapsible loess areas in Gansu and Ningxia in my country. This kind of soil is prone to subsidence when it encounters water, and the side friction parameters are significantly reduced, which seriously threatens the safety of the foundation of the transmission tower. ~ 1.5m thick 2:8 lime soil cushion, and 0.5m thick 2:8 lime soil water-resisting layer is set on the upper part; for a corner tower foundation with a foundation of 1100kV, the 2:8 lime soil volume can reach 1000m 3 , greatly increasing basic investment; moreover, it is difficult for crops to grow in areas where gray soil is used, which will destroy existing cultivated land and bring serious environmental protection problems

[0003] The spiral anchor foundation has been widely used in the stay wire foundation of overseas projects. This type of foundation can significantly reduce the amount of earthwork excavation, construction difficulty and construction cost. The spiral anchor can be firmly embedded in the soil by using its circumferential spiral web In order to provide better pull-out resistance, the composite foundation is formed by using the slab foundation and the spiral anchor below, which can maintain the stability of the overall foundation and prevent the overall foundation from settling after the upper soil meets water; however, the inventors found that , the screw anchor is set directly under the main column and under the floor. Although it can provide part of the uplift bearing capacity, it cannot provide the downforce bearing capacity. Since the slab foundation is buried shallowly, the slab foundation will Uneven settlement will occur, resulting in the overall inability to maintain a horizontal state and inclination. The spiral anchor and pile foundation cannot maintain the stability of the overall foundation when the upper soil meets water, and cannot prevent the offset inclined settlement of the foundation. It is difficult to satisfy the loess area with high collapsibility level

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