Deep Jet Grouting for the Construction of MRT Blue Line Extension in Bangkok-Paper

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The paper describes deep jet-grouting works at Intervention Shaft 2 (IVS.2) for Bangkok’s MRT Blue Line Extension. The treatment was designed to stabilize ground for two short mined connections between the shaft and twin bored tunnels, while limiting surface settlement near buildings and congested Charoenkrung Road.<br /><br />Bangkok’s subsurface comprises highly variable clay and sand layers, with soft, compressible clay near the surface and deeper sandy deposits. A preliminary trial field of 13 columns, drilled to 43.5 m, tested double-fluid jet grouting procedures and parameters. Core sampling, strength and permeability testing, and monitoring of nearby buildings and ground confirmed that the treatment met hydraulic requirements; strength in the upper clay was generally within the specified range, while deeper formations exceeded the specified upper strength limit. Observed building movements stayed within trigger limits.<br /><br />Based on the trials and further ground investigation, the final design focused treatment on the sandy formation, reducing the maximum drilling depth to 37 m and column length to 16 m. The works comprised 176 double-fluid columns and 43 single-fluid columns, treating approximately 3,135 m³ of soil. Special single-fluid columns were added near two buildings to reduce potential stress from compressed air.<br /><br />Despite restricted site space, traffic-management requirements, and the need to handle large volumes of grout-and-soil spoil, the team completed the work on schedule, averaging 2.5 columns per day. The authors conclude that jet grouting can effectively improve soils with varied properties and emphasize the importance of comprehensive trial fields, modern equipment, monitoring, and rigorous quality control.

Keywords

jet grouting

Bangkok MRT Blue Line Extension

Intervention Shaft 2

ground stabilization

double-fluid columns

single-fluid columns

soft clay

sand layers

settlement monitoring

quality control