【作者】 刘坤；

【导师】 胡均平；

【作者基本信息】 中南大学 ， 机械工程， 2013， 硕士

【摘要】 摘要：液压打桩锤由于打击能量大、施工效率高、污染低以及可以实现无级调频调能等优点而广泛应用于预制桩施工。在其打桩过程中,预制桩受冲击锤头频繁的锤击作用经常发生断裂,以及在软土地层施工时可能发生迅速下窜而与桩帽相互脱离,即脱桩发生。此时,高速下落的锤头会以很大的冲击能量对机架和油缸端盖进行空打,损坏设备,危害施工安全,必须予以防护。首先,介绍了液压打桩锤的结构原理、研究现状和发展趋势以及脱桩保护现状,针对打桩锤施工工况和脱桩保护要求,确定脱桩保护系统方案,即采取行程阀和液控换向阀进行脱桩控制,切断油路,利用安全阀以及多孔板式节流小孔和溢流阀相结合的防空打缓冲装置实施缓冲制动。其次,分析了脱桩保护过程能量传递机理,对大流量防空打缓冲装置的结构和参数进行设计,建立缓冲油液压力和温度等状态参数的变化、多孔板式节流小孔的节流特性以及溢流阀的动态特性模型。再次,利用Simulink建立脱桩保护系统仿真模型并得到其缓冲特性,结果表明：溢流阀调定压力和缓冲腔内径对缓冲装置性能影响较大,节流小孔能够改善装置的低速软特性。最后,对脱桩保护系统缓冲特性进行了实验研究,通过测试发现,实验结果和仿真结果吻合度较高,验证了理论研究的正确性和仿真研究的有效性,为液压打桩锤安全施工提供理论依据。更多还原

【Abstract】 Abstract:With the advantages of large piling energy, high construction efficiency, low pollution, energy and frequency adjusted steplessly, hydraulic pile hammer is widely used in prefabricated pile construction. In the piling process, the pre-cast pile, which is frequently impacted by impact hammer, often fractures, as well as occurs rapidly under channeling out of the pile cap on the soft soil, so the off-pile phenomenon take place. In this case, the high-speed falling hammer which owns huge piling energy, will directly impact the crack and cylinder end cap, resulting in equipment damage, against construction safety.Firstly, the principle and structure, research status and development trend of hydraulic pile hammer are introduced, so is the pile detaching protection status. For the hammer construction and conditions and the pile detaching protection requirements, the pile detaching protection system is confirmed. The ystem adopts the stroke valve and hydraulic operated reversing valve to control pile detaching protection system, the hydraulic circuits are cut off, safe valve and the anti-air-strike damper, which consists of multi-hole throttling orifices (MTO) and relief valve attaching to buffer chamber, brake the falling impact piston.Secondly, energy transmission mechanism of pile detaching system are analyzed, structure and parameters of the damper are designed, the state change of pressure and temperature of buffering oil, throttling characteristics of MTO, and dynamic characteristics of the relief valve is modeled.Then, through Simulink simulation model of the pile detaching protection system is established. Buffering characteristics of the damper are analyzed. The study show that set pressure of relief valve and internal diameter of buffer chamber affect performances of the damper significantly, and MTO mainly improve soft characteristics of the damper in low speed.Finally, the pile detaching protection system experiment on its buffering characteristics is done. The testing results show that experimental results and simulation results are mostly the same, so that correctness of theory study and effectiveness of simulation study are verified, theoretical basis for safety construction of hydraulic pie hammer is provided.更多还原