管桩能较好控制工后沉降，与土工格室结合，形成桩网结构路基，其承载更性能优越。为此，本文开展了室内模型试验，对其作用机理和承载特性进行研究。采用了有限元方法建立计算模型，对路基承载性能进一步分析，并优化试验设计参数。主要研究内容与成果如下：

（1）开展了室内模型试验，对管桩-土工格室桩网结构路基的桩身轴向应力、桩土应力比、土工格室的应力以及路基表面的沉降等变化规律进行分析。管桩桩身轴向应力变化表现出摩擦桩的特性，承载力主要是由桩侧摩阻力承担，中心桩桩身轴向应力和桩侧摩阻力均大于其他桩体。桩顶处土压力大于桩间土压力，中心桩的桩土应力比大于边桩的桩土应力比。土工格室的应力随上部荷载的增大而增大，沿路基横断面向路堤边缘方向逐渐减小。路基表面沉降随荷载的增大而逐渐增大。

（2）采用有限元方法建立了管桩-土工格室桩网结构路基的计算模型，与模型试验结果进行对比分析，验证了数值计算的合理性与可靠性，并进一步对桩网结构路基的路基沉降、桩身轴向应力、桩侧摩阻力的变化规律分析。桩网结构路基中，中心桩到边桩的中性点逐渐向下移动，在300 kPa荷载作用下，中性点分别位于桩身2.5 m、3 m、5 m、10.5 m处。由于土拱效应发挥以及桩土刚度差异，路堤内部应力大都向桩体顶部传递。这种桩网结构可以有效减小路基沉降，在荷载作用下，桩顶沉降小于临近桩间土沉降。

（3）利用管桩-土工格室桩网结构路基的计算模型，通过改变桩长、壁厚、桩间距、加筋体类别等对比分析了桩土应力比、路基沉降、桩身轴向应力、土工格室竖向位移等。研究表明，300 kPa荷载作用下，土工格室和土工格栅加筋工况下，相较于单一碎石垫层工况下，中心桩桩顶平面桩土差异沉降分别减小了17.86%、9.13%；路基表面沉降分别减小了5.19%、3.13%；相较于土工格栅，土工格室的三维立体结构可以更好地限制路基表面沉降与桩土差异沉降。不同桩体参数对桩身承载性能的发挥以及桩网结构路基的整体稳定性能都会产生一定影响。通过有限元计算影响因素分析，桩长20 m、壁厚15 cm、桩间距1.8 m（3倍桩径）时，对于控制路基沉降以及桩体内力分布效果最佳。

Pipe piles can better control post-construction settlement. When combined with geocells, they form a pile-net structure roadbed, which has superior load-bearing performance. For this purpose, an laboratory model test was carried out in this paper to study its mechanism of action and load-bearing characteristics. The finite element method was adopted to establish the calculation model, further analyze the bearing performance of the subgrade, and optimize the experimental design parameters. The main research contents and achievements are as follows:

(1) Laboratory model test was carried out to analyze the variation laws of the axial stress of the pile body, the ratio of pile to soil stress, the stress of the geocell and the settlement of the subgrade surface of the pipe pile-geocell pile network structure subgrade. The axial stress variation of the pipe pile body shows the characteristics of a friction pile. The bearing capacity is mainly borne by the lateral frictional resistance of the pile. The axial stress and lateral frictional resistance of the central pile body are both greater than those of other pile bodies. The earth pressure at the top of the pile is greater than that between the piles, and the pile-soil stress ratio of the central pile is greater than that of the side piles. The stress of geocells increases with the increase of the upper load and gradually decreases along the transverse section of the subgrade towards the edge of the embankment. The surface settlement of the subgrade gradually increases with the increase of the load.

(2) The calculation model of the pipe pile-geocell pile net structure subgrade was established by using the finite element method. The results were compared and analyzed with those of the model test to verify the rationality and reliability of the numerical calculation. Furthermore, the variation laws of subgrade settlement, axial stress of the pile body and lateral frictional resistance of the pile net structure subgrade were analyzed. In the pile net structure subgrade, the neutral points from the central piles to the edge piles gradually move downward. Under the load of 300 kPa, the neutral points are located at 2.5 m, 3 m, 5 m, and 10.5 m of the pile body respectively. Due to the exertion of the soil arching effect and the difference in pile-soil stiffness, most of the internal stress of the embankment is transferred to the top of the pile. This pile network structure can effectively reduce the settlement of the roadbed. Under the action of the load, the settlement at the top of the pile is less than that of the soil between the adjacent piles.

(3) By using the calculation model of the pipe pile-geocell pile network structure subgrade, the pile-soil stress ratio, subgrade settlement, axial stress of the pile body, and vertical displacement of the geocell were comparatively analyzed by changing the pile length, wall thickness, pile spacing, and type of reinforcement body. Studies show that under a load of 300 kPa, in the geocell and geogrid reinforcement conditions, compared with the single crushed stone cushion condition, the pile-soil differential settlement at the top plane of the central pile is reduced by 17.86% and 9.13% respectively. The surface settlement of the subgrade decreased by 5.19% and 3.13% respectively. Compared with geogrids, the three-dimensional structure of geocells can better limit the surface settlement of the roadbed and the differential settlement of piles and soil. Different parameters of the pile body will have a certain impact on the performance of the pile body bearing capacity and the overall stability performance of the pile network structure subgrade. Through the analysis of the influencing factors calculated by the finite element method, when the pile length is 20 m, the wall thickness is 15 cm, and the pile spacing is 1.8 m (three times the pile diameter), it has the best effect on controlling the settlement of the subgrade and the force distribution within the pile.