INTERNAL PRESSURE DECREASING METHOD ON TUNNEL EXPERIMENT AND SUITABLE PATTERN FOR TUNNEL ROCK BOLT.

到目前为止，锚杆型式试验一直采用外压法。在该方法中，隧道设置在无应力的基岩中，在基岩周围施加外部压力。在实际中，隧道是在基岩土压力下开挖的。现在更多的认识是，我们采用了内压减压法。设置好内压发生装置后，增加外压，反应中产生内压。通过减小这种压力来模拟开挖。隧道试验装置为平面应变式，尺寸为1.4×1.4×0.3m，模型隧道直径为40 cm。在这些试验中，模型基岩与隧道试验设备之间的摩擦损害了应力传递，隧道壁上的内压没有像预期的那样出现。因此，我们使用聚四氟乙烯阀座和液体石蜡之间来减少摩擦，但仍有一些摩擦量，内部压力变得比外部压力小。因此，我们必须积极增加一些石油单位的内部压力。(1)内压发生装置(φ=40 cm，深度=30 cm)的研制。(2)模型基岩与隧道试验装置之间用聚四氟乙烯底座和液体石蜡摩擦系数的实验研究，以及考虑摩擦的隧道壁面内压控制方法的理论研究。(3)隧道试验内压降低方法的建立。(4)几种锚杆形式(铝筋φ=4 mm，长度=6，12，24 cm)在总锚杆长度相等的情况下的对比试验。从侧压力系数k=1.0的试验结果看，短锚杆比长锚杆更有效。

Up to this time rock-bolt pattern test has been experimented by external pressure method. In that method, tunnel was set in bedrock unstressed, and external pressure is added around bedrock. In actual, tunnel is excavated in bedrock earth-pressured. Now more realizing, we adopt internal pressure decreasing method. After setting the internal pressure generate instrument, external pressure is added and internal pressure occurs in reaction. Excavation is simulated by decreasing this pressure. The tunnel experiment equipment is plane strain type, and its size is 1.4×1.4×0.3m and the model tunnel diameter is 40 cm. In these experiment , friction between model bedrock and tunnel test equipment injures stress transmission and internal pressure at tunnel wall don't occur as expected. So we use Teflon seat and liquid paraffin between them to cut friction, but some mount of friction remain and internal pressure become smaller than external. So we must add some mount of internal pressure actively by oil units. We did followings.(1) Development of the internal pressure generate instrument (φ=40 cm, depth=30 cm).(2) Experimental study of the friction coefficient using Teflon seat and liquid paraffin between model bedrock and tunnel experiment equipment and theoretical study of the control method for internal pressure at tunnel wall considering friction.(3) Establishment of internal pressure decreasing method on tunnel experiment.(4) Comparing experiments with several rock-bolt patterns (aluminum-bar φ=4 mm, length=6,12,24 cm) in the condition total rock-bolt length of each pattern is equal, and non bolt pattern.(5) Short rock-bolt is more effective than long one from the results of experiments on lateral presser coefficient k=1.0.