Soil Stabilization for Cut-Off Wall Works Has Proven Its Function-Paper

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The Rosshaupten Dam at Bavaria’s Forggensee reservoir required rehabilitation after monitoring and investigations identified rising water pressures, seepage, and evidence of suffusion and erosion in the foundation and dam core. The remediation included a 227 m long, 1 m wide cut-off wall extending up to 75 m deep to reduce long-term seepage.<br /><br />Before cut-off wall construction, BAUER Spezialtiefbau carried out pre-treatment grouting in the damaged right abutment. Twenty-four inclined boreholes, drilled to depths of about 80 m, were grouted in stages using the tube-a-manchette method. Sonic drilling through the dam body helped limit the risk of damage, while the GIN method controlled grout pressure and volume. The work installed a grout curtain covering approximately 3,300 m² and used about 280 m³ of cement slurry.<br /><br />Because highly permeable channels could remain, the team also installed Mixed-In-Place (MIP) soil-cement walls on both sides of the planned cut-off wall trench. These 9–11 m deep walls, reinforced with steel beams, were designed to contain the trench if support slurry was suddenly lost and to reduce the risk of collapse. During excavation, such a slurry-loss event occurred; the MIP walls performed their protective function and enabled safe completion of the cut-off wall.<br /><br />Digital monitoring and 3D modelling supported construction planning and excavation. Close cooperation among the owner, consultant, technical expert, and contractor helped deliver the dam’s new seepage barrier safely and economically, allowing reservoir re-impoundment.

Keywords

Rosshaupten Dam

Forggensee reservoir

Bavaria

seepage remediation

cut-off wall

foundation grouting

tube-a-manchette

Mixed-In-Place walls

soil-cement wall

dam rehabilitation