Abstract:Cable is widely used in slope reinforcement engineering;the rules of prestress change in cable are not studied thoroughly and systematically yet,especial the prestress loss after lock and the lasting prestress of cable in mudstone slopes. Based on the systematical monitoring and analysis in the slopes reinforcement project,the prestress loss after lock with short-term and long-term prestress change rules are studied;and also the influence of rainfall on the cable prestress state and the compensation method are monitored and discussed. It is found that the prestress loss after lock is about 12.8%;and the reason is anchorage circle caused by the retraction. After being locked,the prestress loss can be divided into three stages. The first stage lasts about a half month after being locked;but the prestress loss velocity is quickly,about 6.2% in 15 days. It is mainly caused by the creep of mudstone after the cable is locked. Then it becomes into a relatively slow stage:the prestress loss is about 8.1% and the time lasts for about 6 months. Finally,the pretress comes to a steady stage,in this stage the prestress loss is seldom seen but also can be influenced by rainfall etc.. The compensation method can raise the prestress for about 15.4% and also can reduce the lost ratio. By studying the rules of prestress changes in the mudstone slopes,the influencing factors and the compensation method are analyzed.