石灰钉复合框架预应力锚杆支护结构抗拔承载力计算方法

Bearing Capacity Calculation Method of Lime Nail Composite Frame Pre-stressed Bolt

为了解决软土含水量高、强度低所导致的锚杆承载力较低的问题,采用主动与被动加固相结合,提出了石灰钉复合框架预应力锚杆支护结构.对新型结构的组成进行了介绍,深入分析了该结构的工作机理;采用柱孔扩张原理分析了石灰钉膨胀作用下周围土体的附加应力场;建立了石灰钉-钉周土体的渗流固结模型,并采用分离变量法得到固结度的解析解;考虑石灰钉遇水放热所引起的温度变化,并简化为点热源传导模型,求解了温度场;依据温度变化与土体渗透系数之间的关系式,修正了土体平均固结度公式,进而得出考虑石灰钉放热、膨胀和吸水固结作用下锚杆抗拔承载力计算公式;进行了有限元数值模拟与理论解的对比分析,结果表明:(1)新型结构可以有效地降低坡体的孔隙水压力、位移及锚杆轴力;(2)有限元模拟结果与所推导的理论公式结果较为接近,验证了公式的合理性.为该新型结构在工程中的应用提供了理论支持.

To solve the low bearing capacity problem caused by high water content and low strength of soft soil,a new support structure,lime nail composite frame pre-stressed bolt was put forward,which taked into account combining active reinforcement method with passive method.The composition of the new structure was introduced,and working mechanism was analyzed in depth;The principle of cylindrical hole expansion was utilized to describe the additional stress field surrounding soil influenced by expansion of lime nail;The seepage consolidation model of lime nail and surrounding soil was established,the seepage consolidation equation was solved by separation variable method;The lime nail exothermic effect was taken into account,and this effect was simplified to point heat source conduction model,temperature field was determined;Using relationship between temperature change and soil permeability coefficient to correct the formula of average consolidation degree of soil,on this basis,the bearing capacity calculation method of the new support structure was determined;The result of finite element numerical simulation was contrasted with theoretical result,the results are as follows:Firstly,the new structure can effectively reduce the pore water pressure,displacement and bolt axial force of the slope.Secondly,the result of finite element simulation is close to the theoretical formula deduced,which verifies the rationality of the formula.The research of this paper provides theoretical support for the application of the new structure in engineering.