3 Vibro Compaction Profile of Sand Grains Volume reduction due to densification of non-cohesive soils may result in surface settlement of 5% to 15% of the treated depth.
4 Vibro Compaction Design Considerations The design approach for Vibro technologies will generally be governed by one or more of the three major categories of site improvement:Shear resistance increaseSettlement controlLiquefaction & lateral spreading mitigation
6 Vibro Compaction Design Requirements Design of the Vibro program requires information on:Total loads (structure, surcharge, live, wind and seismic)Soil type (variation, stratigraphy, groundwater location)Type of footing/slab designStructural settlement toleranceSite restrictions and limitationsTo address the above issues, the Vibro program is designed such that the zone of influence of the vibratory probe ensures the necessary soil densification and/or reinforcement.
9 Vibro Compaction Design Steps 1. Perform site investigationSoil gradation important2. Calculate performance with existing soil conditionsProblem understood3. Establish compaction requirementsSufficient densification to reduce settlement and/or prevent liquefaction4. Develop appropriate Vibro Compaction approachTreat entire site or just footing?5. Establish testing criteriaRelative density, SPT, CPT, PMT, etc.
10 Vibro Compaction Increased Bearing Capacity Bearing capacity is a function of the soil’s shear strength which is derived from the soil’s angle of internal friction (f) and/or cohesion (c). The Vibro systems increase the allowable bearing capacity by increasing the effective f angle.Vibro Compaction densifies cohesionless granular soils, thus increasing the angle of internal friction directly. The allowable bearing capacity is calculated with conventional procedures using the improved angle.
11 Vibro Compaction Reduced Settlement Settlement is a function of the soil’s modulus and consolidation character. Vibro systems decrease the settlement that will occur beneath a proposed foundation by either directly increasing the in situ soil’s modulus value and/or by constructing high modulus Vibro stone columns in a grid pattern beneath the planned foundation.Vibro Compaction densifies cohesionless granular soils, thus increasing the soil’s modulus value directly. The settlement is calculated with conventional procedures using the improved modulus value.
12 Vibro Compaction Quality Control Compaction point locationsResistance level as measured by amp meter (vibrator drawsmore current in denser soils)Quantity of fill added or reduction in site level
13 Vibro Compaction Acceptance Testing Standard Penetration Test (SPT)Cone Penetrometer Test (CPT)Pressuremeter Test (PMT)Dilatometer Test (DMT)Load test
14 Vibro Compaction Benefits Increases bearing capacity and reduces foundation sizeReduces foundation settlementMitigates liquefaction potentialPermits construction on granular fills