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Abstract Slope protection has always been a major concern in highway construction and later operation. Ecological protection technology is widely used in highway slope, which takes into account functions of protection, ecology, and landscape. Ecological protection technology is mainly to improve the stability of the slope through the combination of supporting structure and plants, and vegetation restoration can reduce the negative impact of highway construction. In this paper, the latest research progress of ecological protection technology was first reviewed to identify the main construction process and types, which revealed the protection mechanism of ecological protection technology. The comprehensive benefits of ecological slope protection technology were analysed from the aspects of air, water circulation, landscape and biodiversity. It has found that ecological protection technology of highway slope mainly forms the atmosphere-plant-soil system. Ecological protection technology of highway slope improved the stability of the slope through the supporting structure and the anchoring effect of plant roots. And the restoration of the surface vegetation on the slope promoted the photosynthesis and transpiration of plants and purifies the air quality along the highway. Ecological protection technology of highway slope could quickly restore the ecological balance, overall landscape and biodiversity of the region.

Embankments filled with disintegrated carbonaceous mudstone (DCM) are prone to uneven settlements because of water-softening property and secondary disintegration of carbonaceous mudstone. To address this problem, nano-Al2O3 and cement were proposed in this study to improve the strength of DCM. Many nano-Al2O3- and cement-modified DCM (NACDCM) specimens with various nano-Al2O3 contents were prepared. Unconfined compression tests and triaxial compression tests were performed to examine the strengths of NACDCM under different conditions. Moreover, X-ray diffraction (XRD) analyses and scanning electron microscopy (SEM) observations were performed to reveal the microscopic mechanism for modification of the NACDCM. Macroscopic results showed that the unconfined compressive strength of NACDCM reached maximum when the nano-Al2O3 content was 0.2%. The cohesion showed positive correlation with nano-Al2O3 content while the angle of internal friction presented negative correlation with nano-Al2O3 content. Moreover, microscopic results indicated that nano-Al2O3 and cement improved the strength of NACDCM, mainly through cement hydration reaction, pozzolanic reaction, ion exchange, gel effect and filling effect.

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