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

迄今为止，锚杆型式试验都是采用外压法进行的。该方法将隧道布置在无应力的基岩中，并在基岩周围施加外压。在实际工程中，隧道是在基岩土压条件下开挖的。现在认识到，我们采用内压降低的方法。设置内压发生器后，加入外压，反应时产生内压。通过降低该压力来模拟挖掘。风洞试验装置为平面应变式，尺寸为1.4×1.4×0.3m，模型洞径为40cm。在这些试验中，模型基岩与隧道试验设备之间的摩擦破坏了应力的传递，隧道壁没有出现预期的内压。因此，我们使用聚四氟乙烯阀座和液体石蜡在它们之间减少摩擦，但仍有一定量的摩擦，内部压力小于外部压力。因此，必须通过供油装置主动增加一定量的内压。我们做了跟踪。(1)内压发生器（φ=40 cm，深度=30 cm）的研制。(2)采用聚四氟乙烯支座和液体石蜡对模型基岩与隧道试验装置之间的摩擦系数进行了试验研究，并对考虑摩擦的隧道壁内压控制方法进行了理论研究。(3)风洞实验中内压降低方法的建立。(4)在锚杆总长度相等的情况下，对铝杆φ= 4mm，长度为6、12、24cm的几种锚杆型式与无锚杆型式进行了对比试验。(5)从侧向压力系数k=1.0的试验结果来看，短锚杆比长锚杆的支护效果好。

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.