The aim of this investigation is to study the downdrag forces on two single piles and relate the forces to the soil characteristics and soil movements. The investigation consists of measurements in two vertical precast concrete piles 10 m apart from each other. They have been driven through a 40 m medium stiff clay and further down to about 15 m depth into the underlying non-cohesive soil. The investigation was divided into three phases: In Phase I, the influence of the pile driving on the soil was studied. Axial pile force and bending moments in the piles were measured. In Phase II, a static load was placed on the pile head in two steps. The influence of the loading on the pile forces and moments was studied. In Phase III, a 1.7 m high surcharge was placed on the ground around the test piles. Measurements of settlements in the soil, pile faces and bending moments were carried out during a period of 2 years. The conclusions drawn from the investigation indicate that during pile driving a pore water overpressure is generated in the soil nearest to the pile. The equalization of this and in connection with obtained reconsolidation and settlement in the soil around the pile, downdrag forces are obtained in the pile. A load in the pile head resulted temporarily in a nearly complete reduction of the arised downdrag forces. Further settlement in the soil also resulted in increased downdrag forces. To obtain maximum negative skin friction between pile and soil the soil's settlement has to be at least 2-4 mm larger than that of the pile. Also a minor relative displacement between pile and soil results in a certain negative skin friction.

  • Corporate Authors:

    Swedish Geotechnical Institute

    S-581 01 Linkoping 1,   Sweden 
  • Authors:
    • Bjerin, L
  • Publication Date: 1977

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 62 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00167825
  • Record Type: Publication
  • Report/Paper Numbers: Report No. 2
  • Files: TRIS
  • Created Date: Mar 7 1978 12:00AM