Long-Term Bearing Capacity of Concrete Pile Composite Foundation under Composite Salt Erosion

Abstract

In order to study the long-term bearing capacity of concrete pile composite foundation in the Salt Lake area, based on the Tehran Isfahan high-speed railway project in Iran, the full (semi) immersion drying test and rapid freeze-thaw test was carried out, and the specimens were scanned by electron microscope. Numerical calculations were used to study the effects of different pile strengths and design parameters on the long-term bearing capacity of the composite foundation. The main conclusions were as follows: The concrete specimens in the adsorption zone deteriorated earlier and faster. In the rapid freeze-thaw tests, the strength attenuation of high-strength (C40, C50) specimens was smaller than that of low-strength specimens (C20). Within 20 years after construction, the additional settlement of low-strength (C20) piles was 12.21 mm, while high-strength concrete was less affected by deterioration. With pile spacing ranging from 1.8 m to 4.5 m, the maximum increase in additional settlement under the C20 condition was about 20 mm. The pile-soil stress ratio under the three conditions increased by 2.42, 6.59, and 8.63. As the pile length and diameter increased, the peak stress of the pile body moved towards the pile end, and the changes in the pile-soil stress ratio under the three conditions were similar.

Service Life of Pre-Tensioned Concrete Structures in a Chloride Environment on the Example of an Aluminium Foundry Building

“…The transport of chlorides through reinforced concrete covers can take place via the mechanisms of diffusion, capillary rise, penetration (when under pressure a solution penetrates into saturated concrete), and migration (the transport of charged ions present in the pore solution under the influence of an electric field) [ 12 , 13 , 14 , 15 , 16 , 17 ]. Diffusion occurs due to the presence of a concentration gradient—when the surface of concrete saturated with water comes into contact with a solution containing chlorides.…”

“…Chlorides penetrate through the filled with water pores of the cement paste. The diffusion of chlorides in saturated pores also takes place during drying [ 16 , 17 , 18 , 19 ]. Capillary rise consists of the penetration of a liquid into empty or partially saturated pores of a hydrophilic material as a result of a negative pressure in the pores.…”

“…In existing structures, the transport of chlorides through concrete often takes place through a combination of transport mechanisms [ 12 ]; for example, when a structural element is subjected to wetting-drying cycles [ 16 ]. During wetting, it is subjected to chloride solution capillary absorption (then possibly diffusion in a wet period), while in dry periods, water evaporation results in the accumulation of chlorides close to the surface.…”