A method and apparatus for forming cemented ground support columns is disclosed. Namely, driving mandrels are provided for the efficient construction of incrementally enlarged diameter support columns. For example, the driving mandrel includes a feed tube that has a top portion and an expansion head portion. The expansion head portion further includes an expansion (or compaction) chamber and a flexible tubular egress port. Further, construction methods are provided of using the driving mandrels for the efficient construction of incrementally enlarged diameter support columns.

A method and apparatus for forming cemented ground support columns is disclosed. Namely, driving mandrels are provided for the efficient construction of incrementally enlarged diameter support columns. For example, the driving mandrel includes a feed tube that has a top portion and an expansion head portion. The expansion head portion further includes an expansion (or compaction) chamber and a flexible tubular egress port. Further, construction methods are provided of using the driving mandrels for the efficient construction of incrementally enlarged diameter support columns.

The present disclosure provides a structural engineering dominated geotechnical structured permanent supporting system and a design method, and belongs to the technical field of underground structures. Through the technical solutions, the structural engineering dominated geotechnical structured permanent supporting system comprises a supporting structure designed on the basis of the partial coefficient of a permanent load, the supporting structure is connected to frame columns of a main structure through a plurality of connecting members arranged at intervals, and a partition wall for blocking soil mass is arranged between every two adjacent frame columns to form a permanent supporting system only bearing soil pressure in the horizontal direction of the supporting structure. When the system is designed, the combined action generated after the main structure and the supporting structure are connected is considered, so that the use of materials is reduced, and the cost is reduced.

The present disclosure provides a structural engineering dominated geotechnical structured permanent supporting system and a design method, and belongs to the technical field of underground structures. Through the technical solutions, the structural engineering dominated geotechnical structured permanent supporting system comprises a supporting structure designed on the basis of the partial coefficient of a permanent load, the supporting structure is connected to frame columns of a main structure through a plurality of connecting members arranged at intervals, and a partition wall for blocking soil mass is arranged between every two adjacent frame columns to form a permanent supporting system only bearing soil pressure in the horizontal direction of the supporting structure. When the system is designed, the combined action generated after the main structure and the supporting structure are connected is considered, so that the use of materials is reduced, and the cost is reduced.

A subgrade with local deep excavation and backfilling structure and a rapid construction method thereof are provided. Supporting cast-in-place piles are laid at positions where an underground pipe gallery is located in a subgrade structure, and soil there between are longitudinally excavated to form a line-shaped foundation pit. A bottom of the line-shaped deep foundation pit is reinforced to support the underground pipe gallery, and lateral peripheral regions and top peripheral regions of the underground pipe gallery are backfilled with block geobag reinforced fillers. Geogrids are placed on the top of the underground pipe gallery, then backfilling compaction and reinforcing are performed, and the geogrids are fixedly assembled with anchor bolts. The construction method is simple and easy. By using compacted block geobag reinforced fillers and cement solidified slurry, an overall quality of the subgrade structure after backfilling can be ensured, and construction period and cost can be greatly reduced.

A subgrade with local deep excavation and backfilling structure and a rapid construction method thereof are provided. Supporting cast-in-place piles are laid at positions where an underground pipe gallery is located in a subgrade structure, and soil there between are longitudinally excavated to form a line-shaped foundation pit. A bottom of the line-shaped deep foundation pit is reinforced to support the underground pipe gallery, and lateral peripheral regions and top peripheral regions of the underground pipe gallery are backfilled with block geobag reinforced fillers. Geogrids are placed on the top of the underground pipe gallery, then backfilling compaction and reinforcing are performed, and the geogrids are fixedly assembled with anchor bolts. The construction method is simple and easy. By using compacted block geobag reinforced fillers and cement solidified slurry, an overall quality of the subgrade structure after backfilling can be ensured, and construction period and cost can be greatly reduced.

Fast-setting flowable fill compositions for filling ground trenches are described. The compositions set quickly but retain a low strength psi at 28 days. The compositions also reduce bleed water on the surface of the fast-setting flowable fill and therefor enable quicker application of surface repair material, e.g., pavement patches, to the trench. The compositions consist of aggregate, Portland cement, accelerant, water and sometimes air. The compositions may have a compressive strength of between 5 psi and 60 psi after 2 hours, a compressive strength of between 10 psi and 100 psi after 4 hours, a compressive strength of between 75 psi and 500 psi after 28 days, a penetration resistance of between 1.5 tsf and 75 tsf after 2 hours, a penetration resistance of between 4.5 tsf and 200 tsf after 4 hours, and a shrinkage of less than 2% as measured by ASTM C490. Also disclosed are methods of filling a trench with fast-setting flowable fill.

Fast-setting flowable fill compositions for filling ground trenches are described. The compositions set quickly but retain a low strength psi at 28 days. The compositions also reduce bleed water on the surface of the fast-setting flowable fill and therefor enable quicker application of surface repair material, e.g., pavement patches, to the trench. The compositions consist of aggregate, Portland cement, accelerant, water and sometimes air. The compositions may have a compressive strength of between 5 psi and 60 psi after 2 hours, a compressive strength of between 10 psi and 100 psi after 4 hours, a compressive strength of between 75 psi and 500 psi after 28 days, a penetration resistance of between 1.5 tsf and 75 tsf after 2 hours, a penetration resistance of between 4.5 tsf and 200 tsf after 4 hours, and a shrinkage of less than 2% as measured by ASTM C490. Also disclosed are methods of filling a trench with fast-setting flowable fill.

A method and apparatus for forming cemented ground support columns is disclosed. Namely, driving mandrels are provided for the efficient construction of incrementally enlarged diameter support columns. For example, the driving mandrel includes a feed tube that has a top portion and an expansion head portion. The expansion head portion further includes an expansion (or compaction) chamber and a flexible tubular egress port. Further, construction methods are provided of using the driving mandrels for the efficient construction of incrementally enlarged diameter support columns.

A method and apparatus for forming cemented ground support columns is disclosed. Namely, driving mandrels are provided for the efficient construction of incrementally enlarged diameter support columns. For example, the driving mandrel includes a feed tube that has a top portion and an expansion head portion. The expansion head portion further includes an expansion (or compaction) chamber and a flexible tubular egress port. Further, construction methods are provided of using the driving mandrels for the efficient construction of incrementally enlarged diameter support columns.