The potential problem with most of the airports are liquefiable fill typically on bay mud. Ports and harbors are also often built on artificial fill which amplifies earthquake shaking. Ports consist of bulk storage facilities and warehouses, cranes to move large containers, and rail and other facilities that serve to connect the port to the land-side transportation system. Liquefaction can cause large areas to sink below the water surface. Rails can buckle, become misaligned, and rotate. Pavement surfaces also buckle, often in ways similar to roadways and airport runways.
Liquefaction prevention is a liquefaction remedial measure for existing structures where other remedial measures cannot be implemented. A perimeter soil-cement cutoff wall is recommended to installed to isolate cohesionless soils under the existing structure. The groundwater within the perimeter cutoff wall is then permanently lowered to provide a dry or non-liquefiable zone under the structure. Reinforcement of liquefiable soils is accomplished by installing soil-cement walls in block, wall or grid patterns to resisit the stress from embankments or other structures when loose cohesionless foundation soil liquefies during seismic ground shaking.
DSM is an in-situ soil mixing technology that mixes existing soil with cementitious materials using mixing shafts consisting of auger cutting heads, discontinuous auger flights, and mixing paddles. The mixing equipment varies from single to eight shaft configurations depending on the purpose of the deep mixing. The soil-cement produced generally has higher strength, less compressibility, and lower permeability than the native soils.
RAS Column is an advanced deep soil mixing method based on mechanical soil mixing technology to produce soil-cement column of 1.4m to 2.5m diameter. The mixing head is equipped with the counter rotation mechanism. This unique mechanism efficiently breaks and mixes in-situ soil with cement-based reagents, producing more homogenous and higher quality soil-cement columns.
SCM (Surface Compact Mixing) is a method to mechanically mix in-situ soil with cement powder or slurry. SCM provides two different mixing equipments, Rotary Blender and Bucket Mixing, to be selected depending on improvement objectives and depth. The unique mixing mechanism provides efficient, cost effective and quality improvement. Larger plant is not necessary. The mixing device can be attached to a local 0.8-1.9m3 excavator.
Jet Grouting is a technique of mixing in-situ soil with the energy of ultra-high pressure jet of slurry. A small-diameter rod drills down to the improvement bottom. Then the rod, while being withdrawn, jets the cement-base slurry and air to produce an improved column. Jet Grouting enables improvement closely contacted to or, in some cases, encompassing existing underground structures without causing damage to them.
The construction of Berths 57/58 at the Port of Oakland required the stabilization of a cut slope under a proposed container wharf extending 2,400 ft. Over 60,000 cubic yards of DSM ground stabilization was constructed over a period of five months. Triple-shaft DSM equipment with a real-time monitoring system was used for ground stabilization.