隧道卸压支护结构相似模拟试验研究

Study on similar simulation test of tunnel pressure relief support

为了研究预留卸压层条件下隧道围岩支护效果,通过聚丙烯纤维和碳纤维宏细观改性泡沫混凝土力学性能,制备充填卸压材料。以老山隧道为工程背景,利用相似模拟试验结合数字散斑测试技术,分析逐级加载条件下隧道围岩受载变形规律。研究结果表明:(1)经宏细观改性后的泡沫混凝土物理力学指标大幅优于普通泡沫混凝土,能有效的抑制和迟滞泡沫混凝土裂纹的扩展,适合作为隧道围岩卸压层充填材料;(2)逐级加载条件下,围岩整体变形位移场呈“人”字形,拱顶预制裂纹沿拱肩方向发展,最后在拱肩深部产生剪切破坏,且较为对称;(3)有卸压层隧道支护比无卸压层隧道支护上的应力减小了30.3%的应力,卸压效果明显。

In order to study the supporting effect of tunnel surrounding rock under the condition of reserved pressure relief layer,the filling and pressure relief material is prepared through the mechanical properties of polypropylene fiber and carbon fiber macro and micro modified foam concrete.Taking the Laoshan Tunnel as the engineering background,the loading deformation law of tunnel surrounding rock under step-by-step loading is analyzed by using similar simulation test and digital speckle testing technology.The research results show that:(1)The physical and mechanical indexes of foamed concrete modified by macro meso scale are much better than ordinary foamed concrete,which can effectively inhibit and retard the expansion of foamed concrete cracks,and is suitable for backfill material of tunnel surrounding rock;(2)Under the condition of step-by-step loading,the overall deformation and displacement field of the surrounding rock is“herringbone”,the prefabricated cracks on the vault develop along the direction of the arch shoulder,and finally shear failure occurs in the deep part of the arch shoulder,which is more symmetrical;(3)The stress of tunnel support with pressure relief layer is reduced by 30.3%compared with that without pressure relief layer,and the pressure relief effect is obvious.