Abstract
In deep season frozen areas, the solidified layer is easy to be destroyed due to the influence of freeze-thaw cycles after the surface layer of the sandy slope is solidified by chemical methods. In order to study the application effect of the new sand consolidating agent after solidifying sand body, the mechanism of strength formation was analyzed by scanning electron microscopy (SEM). The freeze-thaw cycle tests were carried out on sand consolidating samples. The direct shear tests and unconfined compressive strength tests were carried out before and after freeze-thaw cycles to analyze the freeze-thaw resistance of sand consolidating samples. The sand consolidation agent was tested on-site, and its strength was tested to observe its effect. The results showed that the adhesive membranes on the surface of sand particles were formed by the sand consolidating agent, which increased the cohesion and strength of sand particles. After freeze-thaw cycle tests, the cohesion, internal friction angle, and compressive strength of the solidified sand gradually decreased with increasing freeze-thaw cycles. The decreasing rate reduced from fast to slow and then tends to be stable. The failure mode of samples changed from brittle failure to plastic failure. The sand consolidating layer can effectively prevent collapse of the sandy slope. Combining with the external-soil spray seeding, the sand consolidation layer is beneficial to the growth of plants.
Highlights
Aeolian sand is widely distributed in the west and north of China
Changes in Cohesion, Internal Friction Angle, and Compressive Strength. e mechanical parameters, i.e., cohesion, internal friction angle, and compressive strength, were obtained via direct shear tests and unconfined compressive strength tests conducted on the three kinds of sand consolidating samples
After 20 freeze-thaw cycles, the cohesion of the samples made of potassium silicate with modulus 3.2 is 123.46 kPa, which decreases by 30.01%. e internal friction angle is 36.43 degrees, which decreases by 5.18%. e strength is 558.32 kPa, which decreases by 34.81%. e cohesive force of the samples prepared with modulus 3.3 of potassium silicate is 149.53 kPa, which decreases by 31.17%; the internal friction angle is 37.27 degrees, which decreases by 6.50%; and the strength is 682.32 kPa, which decreases by 35.56%. e cohesion of the samples made of potassium silicate with modulus 3.4 is 169.43 kPa, which decreases by 31.47%; the internal friction angle is 37.63 degrees, which decreases by 6.676%; and the strength is 889.96 kPa, which decreases by 36.89%
Summary
Aeolian sand is widely distributed in the west and north of China. At natural state, aeolian sand is loose, which brings some difficulties in the construction of highway engineering in aeolian sand areas. Chemical sand consolidation is to form solidified layers on the surface of aeolian sand to enhance the surface strength. It can keep water in the lower layer so as to achieve the effect of sand consolidation [8]. E new sand consolidating agent TD-1 has good permeability After spraying, it can form a 20–30 cm thick consolidation layer on the surface of aeolian sand and effectively prevent the collapse of sandy slope. Combining with external-soil spray seeding, grass planting can be carried out on the surface of the consolidation layer It has been used in the test section of Zhangjiakou area, and the effect of sand consolidation is good. (i) Potassium silicate: according to the application effect of engineering practice and considering the economic benefits of field use, the ratio of three different moduli (3.2, 3.3, and 3.4) of potassium silicate was studied (ii) New silicon phosphate: the new silicon phosphate is a white powder crystal, which is soluble and can be evenly dissolved in mixed solution (iii) Lithium silicate: the modulus of lithium silicate is 4.8, and the concentration is 0.2 g/mL (iv) Silica sol: silica sol is alkaline (pH 9), and the concentration is 0.3 g/mL
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