圆宝山隧道松散堆积体的力学试验研究

Study on Mechanical Properties of Loose Deposits in Yuanbaoshan Tunnel

松散堆积体在隧道施工中普遍存在,为研究其力学特性,以丽香铁路圆宝山隧道为依托,采用室内试验的方法,对具有代表性的地段进行筛分试验、击实试验及直剪试验。研究结果表明:圆宝山隧道松散堆积体颗粒级配离散性较大,级配不连续,粒径大于2 mm的颗粒质量分数约占50%;击实试验发现,压实度是提高抗剪强度的重要因素,圆宝山隧道松散堆积体的内摩擦角、黏聚力随着压实度的增大而显著增强,压实度、法向应力与抗剪强度基本呈正相关。当压实度为0.9、法向正应力为250 k Pa时,试样的抗剪强度达最大值,为298 k Pa;分析发现,松散堆积体压实度偏小是导致滑坡的重要原因,提高压实度是增大松散堆积体抗剪强度指标的重要手段。

In order to study the mechanical properties of loose deposits, which are commonly found in the process of tunnel construction, by adopting indoor test methods, a compaction test and a direct shear test have been conducted in the representative area of the sampled Yuanbaoshan tunnel in Lixiang railway construction. The results show that the loose deposits of Yuanbaoshan tunnel is characterized with a large discreteness and discontinuous gradation of the grain composition, with its particle size greater than 2 mm, and the mass fraction approximately accounting for 50%. The results of compaction test show that the degree of compaction is an important factor to improve the shearing strength of the tunnel. The friction angle and cohesion of loose deposits in Yuanbaoshan tunnel increase remarkably with the increase of its compactness, with the degree of compaction, normal stress and shearing strength basically positively related. With the degree of compaction being 0.9 and the normal normal stress 250 kPa, the shearing strength of the sample reaches the maximum value of 298 kPa. The analysis shows that the compactness of loose deposits is an important contributing factors of landslide, and the increase of degree of compaction is an important means to increase the shearing strength index of loose deposits.