Conclusions
Bio-cementation tests were conducted to investigate the effects of the
combined MICP-PVAc technology on the improvement of loess-slope surface
erosion resistance. Moreover, PVAc was added to the cementation
solution, which further improved slope stability. The results
demonstrated that MICP-PVAc treatment significantly mitigated surface
erosion of loess-slope. Specific conclusions are outlined as follows:
(1) MICP treatment resulted in an improvement of erosion resistance and
treatment with 6 L/m2 of mixed solution achieved the
best erosion control and the highest surface strength. The soil loss in
MICP treated slopes, however, still remained large. Therefore, a better
treatment was necessary to effectively and efficiently control the
erosion of loess-slope surfaces.
(2) Addition of PVAc had little impact on urease activity and production
rates for calcium carbonate. After treatment with MICP and PVAc
together, the stability of loess-slope improved significantly. For
slopes treated with the addition of PVAc at 40 g/L or 60 g/L, 50 min of
exposure to rainfall caused little soil loss because of the better
cementing effect.
(3) With the addition of PVAc to the cementation solution, the surface
strength of slopes increased beyond that of slopes treated with MICP
only. With 60 g/L PVAc, the surface strength of slope P5 decreased below
that of slope P4, but still remained higher than that of slope P3
because of the lower thickness of cementation.
(4) The high erosion resistance of P4 and P5 was attributed to (1) the
stable spatial structure of CaCO3 precipitation, and (2)
the stronger resistance to tension or shear force from PVAc. The method
proposed in this study provides an effective and efficient t