FOUNDATION STRENGTHENING AND GROUTING BY MEANS OF JET PILES FOR A 9+1-STOREY BUILDING WITH STRENGTHENED-CONCRETE FRAMING
The reinforced concrete frame building on the area of 17 x 150 sq.m consists of a cellar, ground floor and 9+1 storeys. The pillars were founded on solitary reinforced concrete blocks. The given vertical supporting system is horizontally connected by flexible, reinforced concrete sheets for ceiling. This configuration was not adequate to withstand, or balance the ensued uneven settlements arisen by the response of the alternating subsoil under the different loads from the pillars. At frames 14. to 27., however, - which were founded on weak silty fine sand of varying thickness (0.5 to 3.0 m) - the safety factor against failure was calculated to n=1, instead of n=2.77 that had to be prescribed. The goal was to transfer the loads from the silty fine sand onto the Kiscelli clay, which has excellent bearing capacity at 5 to 6 m deeper levels. The first part of the reading to be presented deals with the unavoidable geotechnical exploration, laboratory testing, determination of the intermittent and final time dependent parameters of the jet-propulsion work, the evaluation of the in situ bearing capacity trials and, of the strength analysis of the undisturbed samples having been taken from the jet piles. The second section informs about the design and accomplishment of the work, and concludes with the settlement monitoring results that verified the success. The measurements proved that the settlements stopped at the prescribed limits and, the reckoned safety factors against failure widely surpass the n=2.77 value required by the standard for this case.