【摘要】 为了对锚杆支护设计提供理论依据,本文利用J.Dundurs公式算出了单支锚杆,成组布置锚杆和锚杆桁架在围岩中引起的附加应力场的理论解,(1)、(2)、(3)式。经光弹实验结果分析,证明理论解是正确的。 根据电算的理论解的应力值,文章探索了单锚杆,成组布置锚杆和锚杆桁架的支护机理。并讨论了各种支护参数的选取原则。 本文还讨论了锚杆桁架倾角对压应力分布的影响,认为在锚杆桁架跨度确定后,存在一个最优倾角使压应力值为最大。更多还原

【Abstract】 As an effective safety measure taken to prevent rock-falling in roofed tunnels or slopes,pin timbering has been widely used up to the present.Based upon the simplification and reformation of the expressions in elasticity proposed by J.Dundurs[1][2] and Flamant[3] this paper contributes the theoretical formulas(1),(2)and(3)for the superimposed stress fields due to pin timbering with a single roof bolt,a group of roof bolts and a roof bolt truss,respectively.The photoelastic experiments presenting the stress distributions in rock mass around the anchored roof bolts have been carried out and their results are compared to the theoretical values calculated by a computer with the formulas above-mentioned,thus explaining the rock suspension mechanism of pin timbering.Such a comparison shows that the explanation of the rock-suspension mechanism of pin timbering tallies with the actual situation.In conclusion,——For bolting with a single roof bolt only,the function of pin timbering isonly that it can keep a smaller rock block around the anchored bolt at its original position and keep its fabric intact by compressive stress transmission.——For bolting with a group of roof bolts,the stress distribution in rock mass due to pin timbering can be efficiently improved.The stress field may be divided mainly into three different parts(see Fig.9),i.e.the arched region of tensile stress Ⅰ,the compressive stress region Ⅱ and the secondary tensile stress regionⅢ Region Ⅱ is helpful to improve the rock intensity and to stabilize itself,but the arched region Ⅰ shows a risk of rock failure and,therefore,focuses our attention on the preventive maintenance to it.——For the roof bolt truss,stress analysis shows that the superimposed stressfield close to the rock surface due to pin timbering is further improved and the rock block within a reasonable span of truss always remains in a compressive state.Even if the roof bolt truss exerts a relatively smaller compressive force,the compressive strength in the rock mass parallel to the rock surface may be considerably improved.Moreover,the effect of the bolting inclination of truss on the stress distribution in rock mass is also discussed.更多还原