Malcolm’s drilling and grouting expertise is applied to safely and securely reinforce existing unstable slopes and to allow re-grading for development of new facilities. Our slope stabilization projects employ post-tensioned anchors, stitch piers and dewatering in addition to more conventional retention systems in order to directly resist the slide forces and to increase shear resistance along existing or potential failure surfaces. Detailed geotechnical evaluations identify critical stability conditions and potential sliding mechanisms. Case-specific analysis, design and implementation are required to minimize risk at each stage in the process of enhancing the slope factor of safety for both emergency repairs and long term solutions. Malcolm’s cased drilling methods are ideally suited to the variable ground profiles encountered within slide areas and minimize the hazards associated with the introduction of drilling fluids into marginal ground.
POST-TENSIONED ANCHORS efficiently increase both lateral and shear resistance. Anchors can be drilled over 200 feet fully cased to penetrate and transfer load beyond potential slip planes. Small crawler mounted drills can work from temporary construction benches on marginal slopes. Load resistance is transferred into the slope through reinforced concrete pads bearing directly onto the exposed face, or using a pile and water system.
STITCH PIERS penetrate through the potential slide plane functioning as dowels between the sliding mass and underlying stable ground. These systems rely on arching to transfer slide loading to points of support, both embedment below the slip plane and lateral anchorage close to grade. Malcolm has installed stitch piers ranging from micropiles (less than 12 inches diameter) up to reinforced drilled shafts with 8 feet in diameter. Soil cement columns (SCC) can act to both improve shear capacity of insitu soils and key into firm underlying substrates. Micropiles constructed with “A-frame” configurations create structural efficient systems which develop shear, tension and compression capacity of these elements to resist slide pressures.
RETENTION WALLS, particularly secant pile or soldier pile and lagging walls, are frequently used for slope stabilization. Permanent retention systems are constructed to resist the full slide pressure. Temporary shoring is also employed to allow slope re-grading or construction of shear keys by removal and replacement of weak soil zones within the ground profile.
DEWATERING SYSTEMS enhance slope stability by lowering groundwater levels, increasing effective stress along potential slide planes. Malcolm offers extensive dewatering expertise including horizontal drains, deep wells, eductor wells and well-point systems which can control groundwater and enhance slope safety. In most cases, dewatering is used in combination with other structural systems.