为了寻求更为有效的耗能减振棚洞结构,本研究采用模型试验、LS-DYNA数值计算方法,探究了落球冲击作用下纯砂土垫层、砂土-EPE复合垫层棚洞结构力学响应机制,结果表明:纯砂土垫层下顶板腹部中心位置峰值应变为48.78×10-6,峰值应力为1.46 MPa,接近其极限抗拉强度1.78 MPa;添加6 cm厚珍珠棉(EPE)垫层后该处峰值应变可降低83.42%,等效应力降至0.24 MPa,安全系数可达7.42;当EPE垫层设置厚度由0 cm增至4 cm,Z1、Z2特征位置应变降幅依次可达57.14%、65.22%,当由4 cm增至6 cm时Z1、Z2位置应变降幅为19.05%、18.75%,EPE垫层设置厚度为4 cm时减振效果达到拐点;构建与模型试验尺寸呈1∶1的数值计算模型,增设2、4、6 cm厚EPE垫层后,顶板腹部中心应力由1.16 MPa依次降至0.699、0.418、0.313 MPa,降幅为39.74%、63.96%、73.02%,建议实际防护结构宜设置40~60 cm厚EPE垫层;构建现场实际棚洞计算模型,添加40 cm厚EPE垫层后,中心单元峰值应力由5.71 MPa降至1.72 MPa,降幅为69.88%,落球加速度峰值由546 m/s2降至432 m/s2,降幅为20.88%,验证了砂土-EPE复合垫层可对棚洞结构起到明显防护作用。
In order to find a more effective energy dissipation and vibration reduction shed tunnel structure, this study uses model tests and LS-DYNA numerical calculation methods to explore the mechanical response mechanism of shed tunnel structure with pure sand cushion and sand EPE composite cushion under the impact of falling ball. Through research, it is concluded that the peak strain at the center of the top plate abdomen under the pure sand cushion is 48.78×10-6, the peak stress is 1.46 MPa, close to its ultimate tensile strength of 1.78 MPa. After adding 6 cm thick EPE cushion, the peak strain can be reduced by 83.42%, the equivalent stress can be reduced to 0.24 MPa, and the safety factor can reach 7.42. When the thickness of EPE cushion is increased from 0 cm to 4 cm, the strain reduction at Z1 and Z2 characteristic positions can reach 57.14% and 65.22% respectively. When the thickness of EPE cushion is increased from 4 cm to 6 cm, the strain reduction at Z1 and Z2 positions is 19.05% and 18.75% respectively. When the thickness of EPE cushion is set to 4 cm, the vibration reduction effect reaches the inflection point. Build a numerical calculation model with the size of 1∶1 with the model test. After adding 2, 4, and 6 cm thick EPE cushion, the central stress of the roof abdomen decreases from 1.16 MPa to 0.699, 0.418, and 0.313 MPa, with a decrease of 39.74%, 63.96%, and 73.02%. It is recommended that the actual protective structure should be equipped with 40~60 cm thick EPE cushion. The calculation model of the actual shed tunnel on site was established. After the 40 cm thick EPE cushion was added, the peak stress of the central unit decreased from 5.71 MPa to 1.72 MPa, with a decrease of 69.88%, and the peak ball fall acceleration decreased from 546 m/s2 to 432 m/s2, with a decrease of 20.88%. It was verified that the sand EPE composite cushion can play an obvious protective role on the shed tunnel structure.
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