井下试验 meaning in English

underground trials

The underground tests show that the deformation and roof delamination of roadway surrounding rock can be effectively reduced by means of great increase of the bolt pretensioned stress , the steel strip plays an important role in the rock bolting system , and there exsits a critical value for pretensioned stress , up to or beyond which the rock bolting can effectively control the deformation and damage of the surrounding rock
井下试验表明，大幅度提高锚杆预应力可显著减小巷道围岩变形，有效控制顶板离层；钢带在预应力支护系统中起非常重要的作用；锚杆预应力存在临界值，达到或超过临界值后锚杆支护可有效控制围岩变形与破坏。