Peculiarities of the Calculation and Designing of Foundations with Compacted Base Micropiles (Cbm) for Vertical Load in the Presence of Horizontal Loads and Momenta

ABSTRACT

The article presents the results of investigation of the interaction between the FWM and the compacted soil bases with the action of vertical load on the CBM in the presence of horizontal loads and momenta.

The CBMs have complex (hybrid) construction including the group (cluster) of 3 or 4 cone-shaped micropiles with the length of 1.0 m and uniting their common foundation framework with the height of 0.5 m.

The CBM construction technology provides for driving a special metal punch into and removal from the soil using the standard pile-driving equipment.

The metal well punch of the CBM consists of blockouts of the micro-piles and foundation framework, which are interconnected by a flexure link and driven into the subsoil in the following order: firstly, the blockouts of the micropiles and then the blockout of the foundation framework together with the blockouts of the micropiles. The blockouts are removed from soil in the reverse sequence.

The formed punched cavities (wells for the micropiles and pit for foundation framework) are filled with concrete with reinforcement.

During the construction of the CBM, the double compaction of the subsoil takes place due to driving the blockouts of the micropiles and foundation framework. The intensive compaction of the subsoil leads to high specific bearing capacity of the CBM reaching up to 3,000 kN per 1 m3 of the reinforced-concrete body of the CBM.

The long-term practice of application of the CBM as pier foundations (stand-alone and group ones) has revealed the disadvantages of the methods of their calculation and designing reflected in the technological regulations under the joint action of vertical and horizontal loads and momenta upon them, increasing their dimensions and cost and complicating the manufacturing technology due to enlargement of the CBM in the group (cluster) for the pedestal piers.

The article presents the refined (corrected) technique of calculation of the CBM together with the compacted subsoil under the joint action of vertical and horizontal loads and momenta with due account of three-dimensional nature of work of the CBM and plastic jamming of the CBM in the soil (pile-and-soil massive under the foundation framework and compacted filling around the foundation framework). The cost saving (material consumption and erection) is 30-100% depending on the kind of subsoils.

Keywords: foundation, micropiles, well punch, subsoils, compaction, joint work, loads, momentum, calculation.

For citation: Seskov V., Liakh V.  Peculiarities of the Calculation and Designing of Foundations with Compacted Base Micropiles (Cbm) for Vertical Load in the Presence of Horizontal Loads and Momenta. In: Contemporary Issues of Concrete and Reinforced Concrete: Collected Research Papers. Minsk. Institute BelNIIS. Vol. 8. 2016. pp. 241-252. https://doi.org/10.23746/2016-8-14

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