【作者】 金清平；

【导师】 李小青；

【作者基本信息】 华中科技大学 ， 结构工程， 2011， 博士

【摘要】 土钉支护技术广泛应用于深基坑支护工程中,用钢筋作为土钉支护材料,其高强度的优势没有完全发挥。对于基坑和有些岩土加固属于临时工程,在其使用寿命结束后,每年有数百万吨的钢筋材料被永久埋于地下,造成建材资源大量浪费,侵占、影响地下空间的后续利用,更重要的是会产生锈蚀污染,对土壤与地下水环境造成长远影响。本文结合住房和城乡建设部“十一五”科技支撑计划“地下开挖工程岩土加固关键技术”之子课题“复合材料土钉支护技术研究与示范”,选用轻质高强玻璃纤维复合材料(GFP)土钉与可拆卸木塑复合材料(WPC)面板代替传统的钢筋土钉与网喷混凝土面层,通过室内试验对GFP材料进行了力学性能分析与研究,对WPC面板进行了可拆卸设计,并根据土钉与面板的锚固特点进行了力学分析与验算公式的推导,最后利用FLAC 3D软件对所提出的复合材料支护结构进行了仿真分析比较,验证了复合材料土钉支护的可行性。主要研究结论如下：(1)研究了构成复合材料的增强体、基体等的性质,采用了应用于土钉的复合材料—玻璃纤维复合材料(GFP),分析了土钉支护技术的特点,对传统的土钉材料钢筋和玻璃纤维材料进行了简单比较,纤维复合材料土钉具有抗腐蚀、高强度等钢筋无法比拟的优越特性,而价格方面玻璃纤维和钢筋相差不大,提出玻璃纤维复合材料替代钢筋是合理的,具有较理想的发展前景。(2)选用螺纹表面直径18mm和25mm的GFP杆体进行室内拉伸性能表明：螺纹GFP杆体初期的强度由基体承担,而后期的强度全部由玻璃纤维体承担。承载力会随直径增大而增大,强度随直径增大而减小。对GFP杆体拉伸强度计算公式的修正系数K进行了取值选定,推荐K取0.75是较合理的。(3)对GFP杆体面内剪切强度进行了理论分析和试验,得到直径18mm和直径25mm的GFP杆体面内剪切强度基本相等。进一步论证了按照混合定律确定的理论公式不适用于该GFP材料。本文提出GFP杆体面内剪切强度需要考虑基体和纤维体的粘结力、基体的抗剪强度两部分。对以上杆体进行了抗弯试验,得到弯曲强度变化规律：杆体的直径越小,杆体所能承受的载荷越小。杆体的弯曲强度与直径大小成反比,随着直径增大,弯曲强度却减少,而且减少较快,从性能分析可知导致杆体破坏的并不是拉应力,而是在杆体中性轴以上产生的压应力。同时研究论证了GFP杆体具有较强的耐酸、耐碱、耐盐及耐冻融等抗腐蚀性能。(4)通过试验确定砂浆配比(水泥：砂：水)1：1.5：0.4最适合灌浆,直径18mm的GFP杆体拉拔承载力随着砂浆强度等级提高而提高；直径大小对粘结强度的影响不太明显；当粘结长度达到或超过临界粘结长度时,随着粘结长度的增加,平均粘结应力下降。(5)比较了光面杆体和螺纹杆体的变形、与砂浆体的粘结应力等规律。表明螺纹杆体在受力过程中化学胶着力先发挥作用,然后是摩擦力发挥较大作用,最后是GFP杆体的螺纹与砂浆体之间的机械咬合力发挥作用,其中机械咬合力起主要作用。要切实反映螺纹GFP杆体与砂浆之间的粘结力,需要考虑三类力,因此粘结力理论计算式中需要有分别表示三类力的表达式。(6)提出选用木塑复合材料代替传统网喷混凝土。研发了新型拼接式木塑复合材料土钉墙坡面防护面板,能方便地拼装形成整齐、可密封的面板支护界面,在临时支护工程完工之后能方便地拆卸下来,回收重复使用。并研发了土钉杆体与面板的锚固方式。提出了GFP土钉与WPC面板设计计算的各项指标及公式。(7)应用FLAC 3D对钢筋土钉与GFP土钉进行了施工过程的仿真计算,计算表明GFP土钉所受到的力较钢筋土钉要小且分布更均匀,变化规律有一定的区别。GFP土钉产生的位移要大得多,但都在规定范围之内,符合要求；塑性区基本相同。验证了GFP土钉支护是可行的,在GFP土钉支护施工中需要控制好位移。更多还原

【Abstract】 Soil nailing supporting technology is applied widely in deep foundation pit support engineering, when the reinforcement is used as soil nailing, its advantage of high strength is not fully played. When the foundation pit and some geotechnical reinforcement which used as temporary works reach the end of their useful lives, millions of tons of reinforcement materials are buried permanently under the ground each year, and they cause a large waste of building materials resources, invade and affect the using of the underground space.More important, they will produce rust pollution and cause long-term effect on soil and groundwater environment. According to "Research and demonstration on composite material soil nailing support technology" of "Key technology of rock and soil reinforcement in underground excavation". This paper put forward that glass fiber polymer (GFP) soil nailing with light weight and high strength and removable wood plastic composite (WPC) panel could be used to instead of traditional reinforcement soil nailing and concrete surface layer. GFP rod mechanical properties were tested in door and WPC panel was designed about its disassembly property. Mechanical analysis and the derivation of the formula were done by anchoring features of soil nailing and the panel. At last, the feasibility of GFP soil nailing was verified by the FLAC 3D simulation. The main conclusions are drawn as following:(1) The properties of enhanced body and matrix in composite material were studied, and the soil nailing composite material in application-glass fiber polymer (GFP) was put forward, the features of soil nailing support technology were analyzed. Traditional soil nailing material-reinforcement was simply compared with glass fiber polymer, and the latter had superior properties such as anti-corrosion and high strength, and both of them had little difference on the price. The research proved reasonable that glass fiber polymer instead of the reinforcement, and it will have more broad development prospect.(2) The tensile properties of indoor test on GFP threaded rod with the diameter of 18 mm and 25 mm showed:initial strength of GFP threaded rod is carried by the matrix, and then late strength is carried entirely by glass fiber body. Carrying capacity increases and the strength decreases with the diameter increasing.For the coefficient k,0.75 is recommended in the formula of GFP rod tensile.(3) GFP rod in-plane shear strength was studied and tested, some conclusions were drawn:in-plane shear strength of GFP rod with the diameter of 18 mm and 25 mm are almost equal. In further, theoretical formula from the mixed laws can not be applied to GFP rod. The paper put forward that in-plane shear strength of GFP rod should include two parts:the matrix and fiber adhesion strength, shear strength of the matrix. Bending test was done to the above rods, and the change law of bending strength as follows:GFP rod is smaller in the diameter, bending carrying capacity is smaller. Bending strength is inversely proportional to the diameter size of the GFP rod, bending strength reduces more quickly with the diameter increasing. By properties analysis, the conclusion can be drawn that the failure cause of GFP rod is not tensile stress, but compressive stress. At the same time, the research on corrosion resistance shows that GFP rod has strong acid resistance, alkali resistance, salt resistance and freeze-thaw resistance.(4) Mortar’s mix proportion (cement:sand:water) 1:1.5:0.4 is most suitable for grouting through the test, the carrying capacity of GFP rod with 18 mm in diameter improves with the mortar strength grade increasing; the diameter size affect on bond strength less obviously; when bond length reaches or exceeds critical bond length, average bond stress drops as the bond length increases.(5) The law of the deformation and mortar bond stress between the smooth rod and the threaded rod were compared. It indicated that the progress of the threaded rod carried the force:chemical adhesive plays a prior role ahead of the friction, then the friction plays a larger role, chemical adhesive disappeared,at last the mechanical bite force between GFP threaded rod and the mortar begins to carry the main load, and it is primary role.Three types of force should be considered to reflect effectively bond strength between GFP threaded rod and the mortar, so bond strength theory formulas should include the formula of each force. (6) Wood plastic composite material was put forward to instead of traditional network concrete surface layer. A new type of stitching wood plastic composite panel in soil nailing support for slope protection can be pieced together to form neat and sealable support interface and dismounted, recovered and reused after temporary support has completed.The anchorage of soil nailing and the panel was studied out.The indexes and formulas of GFP soil nailing and WPC panel in design and calculation were put forward.(7) FLAC 3D was used to simulated reinforcement soil nailing and GFP soil nailing construction. The calculation shows that GFP soil nailing carrying load are less and more evenly, and change law has a certain distinction comparing with reinforcement soil nailing. GFP soil nailing has much greater displacement that is within the specified range and meet the requirements. Both is basically the same in plastic zone. GFP soil nailing support is available; the displacement should be controlled in the construction of GFP soil nailing support.更多还原