深埋风积沙地层隧道掌子面失稳特征研究

研究目的:风积沙是一种黏聚力低、自稳能力差的土体,给隧道设计和施工带来很大困难。本文研究旨为揭示不同掌子面角度下深埋风积沙地层隧道的掌子面失稳特征,从而反馈设计施工。研究结论:(1)掌子面前方失稳区呈楔形状,再向上扩展形成封闭的灯泡状区域,随着掌子面角度增大,失稳区下部扩大,上部缩小,掌子面稳定性逐渐改良;(2)掌子面角度对于失稳区的纵向、横向尺寸影响不大,失稳区前边界约为掌子面前方1倍洞径处,横向跨度约为2倍洞径;(3)失稳土体中存在压力拱,其顶点位于拱底上方1~2倍洞径间,随着掌子面角度增大,失稳区形成的压力拱顶点在下移,跨度在减小;(4)本文推导了适用于深埋风积沙地层的掌子面支护力计算公式,并提出了相关设计施工建议;(5)本研究成果可应用于深埋风积沙隧道,尤其是台阶法或盾构法开挖的隧道。

Research on the Instability Characteristics of the Tunnel Face in Deep-buried Aeolian Sand Stratum

Research purposes:Aeolian sand is a soil with low cohesion and poor self-stability,which brings great difficulties to tunnel design and construction.The purpose of this paper is to reveal the instability characteristics of the face of the deep-buried aeolian sand tunnel under different face angles,and to feed back into design and construction.Research conclusions:(1)The instability zone in front of the face has a wedge shape and then expands upward to form a closed bulb-like area.As the angle of the face increases,the lower part of the instability zone expands,the upper part shrinks,and the stability of the face is gradually improved.(2)The angle of the face has little effect on the longitudinal and lateral dimensions of the instability zone.The boundary is about 1 times of hole diameter,and the lateral span is about 2 times of hole diameter.(3)There is a pressure arch in the unstable soil,and the apex is located between the hole and the bottom of the arch.As the angle of the face increases,the apex of the pressure arch formed by the instability zone moves downward and the span decreases.(4)This paper deduces the formula for calculating the support force of the face in the deep-buried aeolian sand stratum,and puts forward relevant design and construction suggestions.(5)The research results can be applied to deep-buried aeolian sand tunnels,especially tunnels excavated by step method or shield method.