LAUSR

Under the effect of load and seasonal rainfall, the disintegrated carbonaceous mudstone (DCM) softens and further disintegrates, causing large settlements and even collapses of the DCM embankments. For this reason, some treatments should be taken to improve the engineering performance of the DCM. In this study, four materials including sodium alginate (SA), calcium chloride (CaCl2), bentonite and nano-Al2O3 were jointly used as modifiers to treat the DCM. The influences of each modifier component on the unconfined compressive strength (UCS), cohesion, angle of internal friction, and coefficient of permeability of the DCM were examined by unconfined compression tests, direct shear tests and permeability tests. The results demonstrated that with the addition of modifiers, the UCS, cohesion and angle of internal friction of the DCM are enhanced, whereas the coefficient of permeability is reduced. The sensitivity analysis showed that the dosage of SA is the dominating factor affecting the engineering performance of the DCM. Thus, special attention should be paid to the dosage of SA when improving the DCM. On the other hand, bentonite is the least important factor for most of the examined engineering properties among the four modifier components. An UCS value that is greater than 1500 kPa was selected as the evaluation criterion, and the stress-strain relationship and failure mode of each sample under unconfined compression were examined. On this basis, eight groups of satisfactory mixing ratios were obtained for the modification of the DCM. It is suggested that when designing mixing ratios of modifiers for the DCM, the recommended SA/DCM ratio is 4%-6%, but the quantities of CaCl2, bentonite and nano-Al2O3 can be adjusted according to the needs and costs.