Abstract
In this study, we applied microbial induced calcium carbonate precipitation (MICP) technology to improve the undesirable characteristics of Pisha sandstone weathered soil that collapses easily upon environmental erosion. Through disintegration tests and wind erosion tests, the anti-water scour and anti-sand erosion performance of the weathered soil was tested before and after the improvement. Combined with an analysis of the physical properties and pore structure of the samples, this paper analyzes the internal mechanism by which MICP technology improves the poor characteristics of the soil. The results show that after improvement with the use of MICP technology, effective cementation is formed between the soil particles to form a solidified material with a strength of up to 1 MPa with a precipitated carbonate content of up to 15%, which effectively improves the water erosion resistance and wind erosion resistance. The disintegration rate of the improved soil sample was only 1.95% at the 30th minute, the remolded soil completely disintegrated, and the undisturbed soil reached 39.64%. The wind erosion resistance of the improved sample is improved, and its coefficient at a 30° erosion angle is increased roughly 20-fold on average when the wind speed is 31 m/s. The internal mechanism of the improved soil when it comes into contact with water and wind is that the induced calcium carbonate crystals fill the pores of the soil particles and adhere to and bridge between soil particles for effective cementation. When the soil expands after water invasion or the soil is destroyed after external erosion, the cementation of mineral crystals on the particles can resist the expansion force and punching force so as to improve the soil’s overall anti-erosion performance.
Highlights
Pisha sandstone is a kind of loose rock strata commonly encountered by local people in the Shanxi, Shaanxi and Inner Mongolia regions of China, which is concentrated in the Ordos Plateau in the north of the Loess Plateau
After the sample is soaked with water, the unconfined compressive strength (UCS) decreases to 446 kPa, and its brittleness is weakened, with its strength remaining at 43.6%
The results show that the improvement method of Pisha sandstone weathered soil based on microbial induced calcium carbonate precipitation (MICP) technology solves the collapsing problem when it is in water
Summary
Pisha sandstone is a kind of loose rock strata commonly encountered by local people in the Shanxi, Shaanxi and Inner Mongolia regions of China, which is concentrated in the Ordos Plateau in the north of the Loess Plateau. It refers to the rock interbedding composed of thick sandstone, sand shale, and argillaceous sandstone from the Paleozoic Permian (about 250 million years) and Mesozoic, Triassic, Jurassic, and Cretaceous periods. It is called a rock, it often presents in a powder like state due to its small thickness of overburden, low degree of diagenesis, and poor structural strength. The survey data show that the distribution area of Pisha sandstone only accounts for about 2% of the Yellow River Basin, the annual amount of coarse sediment, which is the most harmful to the lower reaches of the Yellow River, accounts for about 25% of the siltation. The new methods for environmental management of the Pisha distribution area has always been a research hotspot
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