顶管无中继间长距离下穿河塘施工技术研究

顶管长距离顶进多设置中继间,以保障顶进顺利进行,中继间的设置将提升施工成本,增加施工流程,造成工期延长。对此,研究以济南玉清湖水库至鹊华水厂调水工程为依托,开展顶管无中继间长距离下穿河塘施工技术研究,成功实现了700 m无中继间长距离顶进,研究得到以下结论:无中继间顶进使工作井需要提供更大的顶推力,利用双拼围檩整体连接、底板加厚可提升工作井的整体性;混浆石地层掘进时可利用岩渣形态进行地质判定,并优化泥浆管道、间歇顶进,以降低堵管等风险;研究通过数值模拟给出了长距离下穿河塘的顶进参数,保障了施工的顺利进行。研究成果对长距离下穿河塘顶管施工具有良好的借鉴意义。

分仓注浆减阻方式在长距离顶管中的应用

某电力管廊工程采用顶管施工,最大顶进长度达445 m,如何降低顶力是实现无中继间一次顶进的关键。为减少摩阻力以降低顶力,在管节上增加钢筋环,加大管节与土体之间的间隙,形成厚泥浆套以降低摩阻力,并形成分区注浆机构,储蓄泥浆,保证减阻效果。分析顶进过程顶力、摩阻力及注浆压力的变化规律,得出结论:监测计算得出的最大顶力低于目标控制顶力,并相对理论总顶力降低了约33.42%;摩阻力大幅降低,使得大管径顶管在不采用中继间的情况下实现超长距离一次顶进;泥浆套厚度的增大需增加注浆效率和压力;增大注浆压力后,地面无冒浆和隆起现象,且周边沉降符合设计要求。

长距离顶管分级顶力控制方法研究

某电力管廊工程需进行超长距离顶管施工,对顶进过程顶力进行合理控制是保证工程顺利顶进的关键。采用理论计算与实际监测相结合的方法,进行超长距离顶管的分级顶力控制研究。详细介绍了顶力控制系统和分仓注浆减阻措施,重点研究了顶力的理论计算和变化趋势预测,并给出了分级顶力控制措施,最后验证了分级顶力控制技术的应用效果及适用性。研究结果表明,分级顶力预测结果与实测结果相符;通过采取分级顶力控制措施及分仓注浆减阻措施,实际顶力较理论顶力降低了约31.32%,并实现了无中继间超长距离一次顶进。研究结果可为类似顶管工程进行分级顶力控制提供参考。

泥水平衡顶管机在城市非开挖管线工程中的应用

非开挖技术是指利用各种岩土钻掘设备和技术手段，在地表不开挖沟槽的条件下，铺设、更换或修复地下管道、电缆、电线等公用设施且不影响任何交通和设施的正常运行，做到最小限度地扰民碍市。机械顶管施工技术广泛应用于管线施工中，通过对泥水平衡顶管机直顶钢管施工的研究，总结出了1套成熟的给排水管道非开挖施工技术，以供类似工程参考与借鉴。

Bidirectional secondary transmissions with energy harvesting in cognitive wireless sensor networks

To the existing spectrum sharing schemes in wireless-powered cognitive wireless sensor networks,the protocols are limited to either separate the primary and the secondary transmission or allow the secondary user to transmit signals in a time slot when it forwards the primary signal.In order to address this limitation,a novel cooperative spectrum sharing scheme is proposed,where the secondary transmission is multiplexed with both the primary transmission and the relay transmission.Specifically,the process of transmission is on a three-phase time-switching relaying basis.In the first phase,a cognitive sensor node SU1 scavenges energy from the primary transmission.In the second phase,another sensor node SU2 and primary transmitter simultaneously transmit signals to the SU1.In the third phase,the node SU1 can assist the primary transmission to acquire the opportunity of spectrum sharing.Joint decoding and interference cancellation technique is adopted at the receivers to retrieve the desired signals.We further derive the closed-form expressions for the outage probabilities of both the primary and secondary systems.Moreover,we address optimization of energy harvesting duration and power allocation coefficient strategy under performance criteria.An effective algorithm is then presented to solve the optimization problem.Simulation results demonstrate that with the optimized solutions,the sensor nodes with the proposed cooperative spectrum sharing scheme can utilize the spectrum in a more efficient manner without deteriorating the performance of the primary transmission,as compared with the existing one-directional scheme in the literature.