【作者】 刘延东；

【导师】 陈锐； 付文光；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2021， 硕士

【摘要】 土层锚杆锚固技术具有施工灵活、成本低、污染小等优点,在岩土工程中应用广泛。实际工程中,应用在土层中的锚杆种类繁多,但受研究条件的限制,目前针对不同类型锚杆的对比研究多采用理论研究和室内模型试验的方法,较少开展现场试验对不同类型锚杆的承载特性进行对比分析。同时,锚杆的判稳指标是现场试验过程中确定锚杆承载力的标准,在现场试验过程中起着至关重要的作用,不合理的判稳指标会造成对极限承载力的误判,影响工程安全和经济效益。针对以上问题,本文基于现场试验,研究花岗岩残积土锚杆判稳指标及不同类型锚杆承载特性,并借助数值方法,对现场无法监测到的锚杆应力分布开展进一步研究。现场试验现象分析表明,花岗岩残积土中全粘结、拉力型、拉力二次注浆和压力型锚杆均为锚土界面拔出破坏,且锚土界面破坏并不是紧贴锚固体表面发生的,而是存在于靠近锚固体的土体内部。基于现场试验对现行规范中的锚杆判稳指标进行对比分析,结果表明规范判定的极限承载力与现场试验结果存在一定的差异。而本文基于蠕变率建立的判稳指标在锚杆极限承载力的判定中准确度较高且较为稳定,适用于花岗岩残积土中锚杆,在现场锚杆试验的判稳中具有一定使用价值。四种类型锚杆承载特性对比分析表明,全粘结锚杆、拉力型锚杆和拉力二次注浆型锚杆的承载特性表现出高度的一致性,这三类锚杆在不同长度下的极限承载力和极限状态锚土界面平均剪应力基本相同,且在18 m的长度范围内没有表现出临界锚固长度效应。随着锚固长度的增加,这三类锚杆的极限承载力呈线性增长趋势,界面平均剪应力基本不变,极限位移呈非线性增长趋势且增长速度越来越快。而压力型锚杆承载特性与另外三类锚杆差异较大,极限承载力和极限位移随锚固长度增加呈现出收敛趋势,在9 m-18 m范围内临界锚固长度效应明显,界面极限剪应力随锚固长度增加不断降低。利用数值模拟方法,对拉力型锚杆和压力型锚杆的应力分布进行对比分析。研究表明,拉力型锚杆应力分布和压力型锚杆应力分布有较大差异。其中,拉力型锚杆的正应力峰值和锚土界面剪应力峰值均出现在靠近锚固体端部的位置,而压力型锚杆的应力峰值均出现在锚固体底部。同时,对比两类锚杆的锚土界面应力分布发现,压力型锚杆应力分布更不均匀,应力集中现象更明显。更多还原

【Abstract】 Soil bolt anchoring technology has the advantages of flexible construction,low cost and low pollution,and is widely used in geotechnical engineering.In practical engineering,many kinds of anchor bolts have been applied in soil layer.However,due to the limitation of research conditions,the current comparative research on different types of anchor rods mostly adopts theoretical research and indoor model tests,and few field tests are carried out to compare and analyse the bearing characteristics of different anchors.Meanwhile,the stability index of anchor bolt plays a vital role in determining the ultimate bearing capacity of the anchor bolt in field test.Unreasonable stability index will lead to misjudgment of the ultimate bearing capacity,which will threaten the engineering safety and cause casualties and property losses.To solve the above problems,based on the field test data,this study researched the stability index of anchor bolts in granitic residual soil and the bearing characteristics of different types of anchor bolts.With the help of numerical method,the stress distribution of bolts which can not be monitored in the field was further studied.Through the analysis of field test phenomena,there are four types of anchor bolts in graniteic residua soil: full bond,tension type,tension secondary grouting and pressure type are pull-out failure of anchor soil interface,and the failure of anchor soil interface does not occur close to the surface of anchor bolt,but exists inside the soil close to the anchor bolt.Based on the field test data,the different stability indexes of anchor bolts in current norms are compared and analyzed.The results show that there are some differences between the determined ultimate bearing capacity that current norms define and the field test results.The stability index established based on creep rate in this study has higher accuracy and stability in determining the ultimate bearing capacity of anchor bolts,which can be used for granitic residual soil anchor bolts and has practicable value in field test of judging stability.The comparative analysis about the bearing characteristics of four types of anchor bolts shows that the bearing characteristics of fully bonded anchor bolts,tension anchor bolts and tension secondary grouting anchor bolts are highly consistent.When these three types of anchor bolts are under limit state,the ultimate bearing capacity of different lengths and the average shear stress of anchor soil interface are basically the same.No critical anchor length effect was shown in the length range of 18 m By the increase of anchorage length,the ultimate bearing capacity of these three types of anchor bolts increases linearly,the average shear stress at the interface are basically unchanged,and the ultimate displacement increases nonlinearly and faster.Howere,the bearing characteristics of pressure anchor are quite different from the other three types of anchor.The ultimate bearing capacity and ultimate displacement show a convergence trend wit h the increase of anchor length.The critical anchor length effect is obvious in the range of 9 m-18 m,and the interface ultimate shear stress decreases with the increase of anchor length.The stress distribution of tension anchor and pressure anchor are compared and analyzed by numerical simulation method.The research showed that the stress distribution of tensile anchor and pressure anchor stress are quite different.Among them,both the peak positive stress of the tensile anchor and the interface she ar stress at the anchor soil appear near the anchor solid,while the peak stress of the pressure anchor appears at the bottom of the anchor solid.At the same time,compared with the anchorage interface stress distribution of the two types of anchors,the anchor stress distribution is more uneven,and the stress concentration phenomenon is more obvious.更多还原