US Patent No. 10,655,280

CONSTRUCTION METHOD FOR USING MODIFIED PHOSPHOGYPSUM IN ROADBED AND SLOPE


Patent No. 10,655,280
Issue Date May 19, 2020
Title Construction Method For Using Modified Phosphogypsum In Roadbed And Slope
Inventorship Zhiqing Li, Beijing (CN)
Assignee INSTITUTE OF GEOLOGY AND GEOPHYSICS, CHINESE ACADEMY OF SCIENCES, Beijing ...

Claim of US Patent No. 10,655,280

1. A design and construction method for using modified phosphogypsum in a roadbed and slope, wherein the method comprises the following steps:(1) preparing a phosphogypsum-containing roadbed mixture (1): weighing 90 parts by weight of phosphogypsum and 10 parts by weight of cement, and uniformly mixing and stirring the phosphogypsum and the cement to obtain a base material mixture; and weighing 2-4 parts by weight of sodium silicate, dissolving the sodium silicate in water, and adding an obtained solution to the base material mixture to obtain the phosphogypsum-containing roadbed mixture (1);
(2) mixing the phosphogypsum-containing roadbed mixture (1) with water: acquiring a part of the phosphogypsum-containing roadbed mixture (1) by using an isostatic pressing method, adding water to prepare samples with different water content, and obtaining maximum dry density and optimal moisture content of the phosphogypsum-containing roadbed mixture (1) in a same compaction energy condition;
(3) adding water to the phosphogypsum-containing roadbed mixture (1) according to the optimal moisture content obtained through the test, to make moisture content of the phosphogypsum-containing roadbed mixture (1) reach the optimal moisture content, to obtain a roadbed filler, where mixing of the phosphogypsum-containing roadbed mixture (1) is conducted in a plant mix manner by using a stock bin of a cement stabilized soil mixing station and a forced mixer; and an anti-seepage cushion layer is an anti-seepage geotechnical cloth or an anti-seepage geomembrane with a thickness not less than 1.0 mm;
(4) preparing a phosphogypsum-containing slope mixture: weighing 50 parts by weight of phosphogypsum and 50 parts by weight of planting soil, and uniformly mixing and stirring the phosphogypsum and the planting soil to obtain a slope mixture; and
(5) transporting the roadbed filler and the slope mixture to a construction site, wherein a specific construction method comprises the following:
1) leveling and compacting original ground, and laying a soil filler above a groundwater level and a surface water level, wherein a loose laying depth of each layer of laid soil filler is not greater than 40 cm, and compactness is not less than 90%;
2) laying a first anti-seepage cushion layer (2) on a full section of a top surface of a compacted soil-filled roadbed;
3) laying a first soil filler layer (3) on a full section of the first anti-seepage cushion layer (2), wherein a loose laying depth of the first soil filler layer (3) is not greater than 40 cm; conducting compaction and densification on the first soil filler layer (3) in a condition of optimal moisture content; and laying a second anti-seepage cushion layer (4) on a full section of the top surface of the first soil filler layer (3);
4) laying a second soil filler layer (5) on a full section of the second anti-seepage cushion layer (4), wherein a loose laying depth of the second soil filler layer (5) is not greater than 40 cm; conducting compaction and densification on the second soil filler layer (5) in a condition of optimal moisture content, and laying a third anti-seepage cushion layer (6) on a full section of the top surface of the second soil filler layer (5);
5) laying the phosphogypsum-containing roadbed mixture (1) on a part of the top surface of the third anti-seepage cushion layer (6), wherein a loose laying depth of each layer of phosphogypsum-containing roadbed mixture (1) is not greater than 40 cm; conducting isostatic compaction and densification in a condition of optimal moisture content; and laying a road-shoulder soil filler (7) on two sides of the top surface of the third anti-seepage cushion layer (6), wherein a laying width of the road-shoulder soil filler (7) on each side along a roadbed section direction is not less than 1.5 m, and a loose laying depth of each layer of road-shoulder soil filler (7) is not greater than 40 cm; and conducting compaction and densification on the road-shoulder soil filler (7) in a condition of optimal moisture content;
6) after the phosphogypsum-containing roadbed mixture (1) and the road-shoulder soil filler (7) are compacted to an upper embankment by layer, laying a fourth anti-seepage cushion layer (8) on full sections of the top surfaces of the phosphogypsum-containing roadbed mixture (1) and the road-shoulder soil filler (7); laying a third soil filler layer (9) on a full section of the fourth anti-seepage cushion layer (8), wherein a loose laying depth of the third soil filler layer (9) is not greater than 40 cm; and conducting compaction and densification on the third soil filler layer (9) in a condition of optimal moisture content, so as to form a filling roadbed; and
7) after the slope mixture is brushed to a design position as required, first hanging a wire entanglement; cultivating the phosphogypsum-containing slope mixture to the surface layer of the roadbed and slope, wherein a cultivation thickness is between 5 cm and 8 cm; spray-seeding grass and shrub seeds; and conducting greening protection.