## 1 Introduction  
Water is one of main factors in the instability of weak rock slope, which has a significant influence on the balance of the internal structure of rock mass [1; 2; 3]. In essence, the softening and instability collapse of weak slopes are mainly attributed to the interaction of internal structures of water-weak rock mass. [PERSON] et al. believed that the interaction between water and weak rock was mainly the process of dissolution-reprecipitation and physical and chemical reactions, such as ion exchange. In this process, the increase in volume and the decrease in the strength of rock mass could result in slope instability [4; 5; 6]. Some scholars have studied the saturated and unsaturated seepage of rock mass fissures through numerical simulation. It has been shown that the seepage of rock mass changed greatly and expanded continuously, which had great influence on the stability of the slope [7; 8; 9; 10]. Water can destroy the tiny minerals and pore structures on the surface of the rock mass, thus affecting the stable microstructures of the rock mass. These mineral and microstructural changes can cause shallow slope damage. When water exists in the slope for a long time, it can reduce the ultimate compressive pressure of the rock mass, which eventually results in deep creep deformation [11; 12; 13].  
Therefore, as long as the contact between the water and the weak slope surface is prevented or reduced, the softening of the weak slope can effectively be slowed down.  
At present, traditional masonry protections, such as grouted rubble masonry, dry rubble masonry, and spray concrete with steel bar nets, have been generally adopted in weak rock slope protection worldwide. Although weak rock slope could effectively be prevented from collapsing, the strength and efficiency of protection has been excessively pursued resulting in the destruction of the harmony of natural ecology so that green trees and clean rivers have been replaced by the hard and rigid \"cement channel\" that was constructed in slope protection engineering [14; 15; 16]. The construction of landscape effects and the normal growth of plants at that time were mainly focused on the nowadays commonly used methods of ecological protection of weak rock slope. However, the denudation and softening of weak rock slope and the overall structural instability could not be prevented [17; 18; 19]. The curing materials for these slopes have developed from the original single cement, fly ash, or lime into the new curing materials, such as the slope-curing agent. The slope-curing agent refers to the composite material which can improve the stability of engineering slope. It can also overcome and improve the shortcomings of single materials, such as cement, fly ash, and lime. Most studies focus on the solidification and modification of soil slopes [20; 21; 22]. However, the polymer curing agent may have different effects on the ecological protection of weak rock slopes after it is used for slope curing.  
The new polymer curing agent was mainly proposed in terms of hydration disintegration, water softening, strength reduction, and other characteristics of weak rock. It can prevent, weaken, or slow down the softening, disintegration, and collapse of weak rock slopes, thus improving the long-term stability. The external-soil spray-seeding technology with microbial polymer water-absorbing material was carried out in the green ecological protection of slopes, which played a role in improving the stability of weak slopes and thus created a safe, green, and environmentally friendly road operation environment.