小直径水泥土桩在软土既有铁路顶桥中的应用研究

The Applied Research of Micro-pile in the Existing Railway Jacking Frame in Soft Soil Area

为解决软土地区既有铁路顶桥过程中的掌子面坍塌问题,研究采用小直径水泥土桩的形式对掌子面进行加固,从设计方法、施工工艺和现场试验的角度开展研究。研究结论:(1)提出了小直径水泥土桩应用于软土地区顶桥过程中掌子面加固的设计方法;(2)上排小直径水泥土桩以承受剪力为主,下排小直径水泥土桩以承受拉力为主。因此,小直径水泥土桩桩身宜较为粗糙,以便增强与周围土体的整体性;(3)研制了适用于软土地区的小直径水泥土桩施工机具。试验结果表明,施工过程中对地面的最大扰动值为3.6 mm;成桩强度与水泥的掺量有关,单轴抗压强度为4.08~10.24 MPa,劈裂抗拉强度为1.64~2.40 MPa,黏聚力为8.6~10.9 MPa,内摩擦角为19~24°;(4)现场开展了压载试验,试验结果表明,采用小直径水泥土桩提高了掌子面的稳定性,与理论分析较为吻合。

To solve the tunnel face collapse problem during the existing railway jacking bridge in soft soil area,micropile is adopted in the study to reinforce the tunnel face. Researches are conducted from aspects of design method,construction process and field test. Researches conclusions：（ 1） the design method for the reinforcement of tunnel face with micro-pile during jacking bridge process in soft soil area is put forward.（ 2） The upper micro-piles mainly bear shearing force,while the lower micro-piles mainly bear tensile force,so the body of the micro-pile should be relatively rough to improve the integrity with surrounding soil.（ 3） The small diameter cement pile construction equipment is developed for soft soil area. The test results show that the maximum disturbed value against the ground is 3. 6 mm; the pile forming strength is related to cement content,the uniaxial compressive strength is 4. 08 - 10. 24 MPa,splitting tensile strength is 1. 64 - 2. 40 MPa,cohesion intercept is 8. 6 - 10. 9 MPa,internal friction angle is 19 - 24°.（ 4） Field loading test is conducted and the test results show that the stability of the tunnel surface is improved by using micro-pile,which is consistent with the theoretical analysis.