The Malan loess is a greyish yellow unstratified sediment with uniform lithology, large pores and loose texture. The Malan loess is sensitive to water due to its porous and metastable structure. Water‐induced disintegration is the main cause of soil loss in the Loess Plateau of China and the primary evolutionary driving force of the loess landform. A series of laboratory tests is conducted on undisturbed cylindrical Malan loess samples to understand their disintegration behaviour further and examine potential influencing factors. Results show that the Malan loess experiences primary and secondary disintegration stages. The primary disintegration occurs very fast and terminates in an average of 40 s. Approximately 78% of the soil disintegrates in this stage. The disintegration velocity (V) and percentage (Df) in the primary stage demonstrate high correlation with the dry density, clay mineral content and CaCO3 content. Specifically, Df increases while V decreases with the increase of dry density or clay content. Df decreases while V increases with the increase of CaCO3. The concentration of ions, including Cl−, SO42−, CO32−, HCO3−, Ca2+, K+, Na+ and Mg2+, and the organic matter content do not exhibit a clear relationship with Df and V. In addition, the pore structure influences the Malan loess disintegration. The soil with evenly distributed small pores is subjected to gradual disintegration from outside to inside without abrupt failure, while that with large pipes disintegrates abruptly in large pieces.
In the past decade, the wireline robot has received increasing attention due to the advantages of light weight, low cost, and flexibility compared to the traditional drilling instruments in space missions. For the lunar subsurface in situ exploration mission, we proposed a type of wireline robot named IBR (Inchworm Boring Robot) drawing inspiration from the inchworm. Two auger tools are utilized to remove chips for IBR, which directly interacted with the lunar regolith in the drilling process. Therefore, for obtaining the tools drilling characteristics, the chips removal principle of IBR is analyzed and its drilling load model is further established based on the soil mechanical theory in this paper. And then the proposed theoretical drilling load model is experimentally validated. In addition, according to the theoretical drilling load model, this paper discusses the effect of the drilling parameters on the tools drilling moments and power consumption. These results imply a possible energy-efficient control strategy for IBR.
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