铁路作为重要基础设施，在我国运输网络中起着重要作用。桩网结构路基因其施工周期短，工后沉降小等特点，在国内高铁路基工程中应用广泛。然而桩网结构路基受力机理十分复杂，对其荷载传递、分配规律以及动力响应的研究不够充分。本文采用室内试验与有限元方法对其荷载传递规律进行研究，主要工作如下：

（1）通过大型室内模型试验研究了桩网结构路基在五级静力荷载下的桩身应力应变、桩土荷载分担比、路堤内部土压力分布特征、土拱效应的发展与分布规律、以及格栅垫层的应力分布特点。试验结果表明：桩体承载力主要表现为桩侧摩阻力；土工格栅横向拉力由路堤中心向坡脚处递减；路基横向土压力大于纵向；空间土拱效应极限状态出现在桩土应力比3.8左右，平面土拱效应极限状态出现在桩土应力比2.2左右，空间土拱效应比平面土拱效应更强。

（2）通过对桩网结构路基施加动载，探究其在动载下的桩土应力分布、路堤内土动应力分布、动载下土拱效应的发展变化规律，并与静载试验进行对比，结果表明：动载下土拱效应较静载有一定衰减，且静载下土拱效应越强的部位在动载下削弱程度越大；桩间土动应力随振次的变化趋势类似“N”型，与桩顶土动应力的变化趋势正好相反；格栅拉力在动载下约为相同大小静载下的2倍。

（3）建立了桩网结构路基三维数值计算模型，揭示了结构的荷载传递规律及动力响应规律。分析了路堤填土高度、桩间距等主要参数对桩网结构路基力学性能和土拱效应的影响。模拟了时速300km的列车荷载对结构的动力响应。结果表明：土工格栅的荷载传递是由路基中轴线向坡脚呈波浪形发展的；土拱在路基横断面呈波浪形分布；桩间距扩大能够增大土拱高度、扩大土拱效应的影响范围但土拱强度会减弱；路堤高度对土拱效应的影响不明显；动载下路堤内部土拱效应分布特点和静载相同，但较静载有大幅削弱。

As an important infrastructure, railway plays an important role in China's transportation network. Pile network structure roadbeds are widely used in domestic high-speed railway roadbed projects due to their short construction period and low post-work settlement. However, the force mechanism of pile network structure roadbed is very complex, and the research on its load transfer, distribution law and dynamic response is not sufficient. In this paper, laoratory  tests and finite element methods are used to study its load transfer law, and the main work is as follows：

(1) The stress-strain of the piles, the pile-soil load sharing ratio, the soil pressure distribution inside the embankment, the development and distribution of the soil arch effect, and the stress distribution characteristics of the grid bedding layer were investigated through large scale laboratory model tests. The test results show that: the pile bearing capacity is mainly expressed as pile lateral friction resistance; the tensile force of the geogrid decreases in the transverse direction from the centre of the embankment to the foot of the slope; the transverse soil pressure of the roadbed is greater than the longitudinal direction; the limit state of the spatial soil arch effect occurs at about 3.8 pile soil stress ratio, and the limit state of the planar soil arch effect occurs at about 2.2 pile soil stress ratio, and the spatial soil arch effect is stronger than the planar soil arch effect. stronger than the planar soil arch effect.

(2) By applying dynamic load to the pile network structure, the pile soil stress distribution, embankment soil dynamic stress distribution and the development of soil arch effect under dynamic load were investigated and compared with the static load test, and the results show that: the soil arch effect under dynamic load is definitely attenuated compared with static load, and the stronger the soil arch effect under static load, the greater the degree of weakening under dynamic load; the change trend of soil dynamic stress between piles with vibration is similar to the "N" type, which is the opposite of the change trend of soil dynamic stress at the top of piles; the grating tension under dynamic load is about twice that under static load of the same size.

(3) A three-dimensional numerical calculation model of the pile network structure roadbed is established to reveal the load transfer law and dynamic response law of the structure. The influence of the main parameters such as embankment fill height and pile spacing on the mechanical properties of the pile network structure roadbed and the soil arch effect is analysed. The dynamic response of the structure was simulated for a train load at a speed of 300km per hour. The results show that: the load transfer of the geogrid is wavy from the central axis of the embankment to the foot of the slope; the soil arch is waved in the cross section of the embankment; the increase of the pile spacing can increase the height of the soil arch and expand the influence range of the soil arch effect but the strength of the soil arch will be weakened; the influence of the embankment height on the soil arch effect is not obvious; the distribution characteristics of the soil arch effect inside the embankment under dynamic load are the same as that of static load, but it is significantly weaker than that of static load.

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