Experimental investigations of pile loads and foundation settlements in tall large-panel buildings

Abstract

1. During the process of settlement of pile foundations with and without gratings in the nine-story large-panel frameless buildings with transverse and longitudinal bearing walls, the loads were redistributed and equalized, which was a consequence of interaction between the relatively rigid building box and the pliant base of the foundation. 2. Field investigations of the actual pile loads in the foundations of the nine-story large-panel buildings made it possible to establish that the design pile loads exceeded the actual values by 12–16%. 3. The nature of the distribution of the forces in the elements of the pile foundations of the large-panel frameless buildings indicates the need for taking into account the pliancy of the soil base of the pile foundation and its joint operation with the constructional components of the building box for determining the pile loads and for designing the gratings as well as the wall panels with gratingless support. 4. In the pile foundations of the nine-story frameless large-panel buildings with load-bearing, frequently transverse walls of the type of Series 1-464D, with and without gratings on compressible soils, the loads in piles with equal rigidities of the soil bases can be assumed to act as uniformly distributed, as an approximation, in engineering analyses. In the case of different rigidities of the soil bases of the piles, the load on each pile can be determined as a force proportional to the corresponding rigidity. 5. The actual settlement of the pile foundation of the large-panel building on alluvial soils was greater by a factor of 5–6, and for the building on the clay soils of the Ufa floor it was greater by a factor of 15 in comparison with the settlement of a single pile constructed on the basis of the same static test results, under the same soil conditions, and for the same loads. Hence, the coefficient ζ recommended in the SNiP II-17-77 for transfer from settlements of individual piles in static tests to settlements of piles in foundations under long-term loading should be differentiated according to the soil type and state.