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171.
砂卵石地层土压平衡盾构隧道施工土体改良试验研究 总被引:2,自引:0,他引:2
盾构机在卵石含量高、粒径大的砂卵石地层中掘进时,由于土体塑流性差,土体在土舱内无法及时排出,时常出现盾构推力、刀盘扭矩异常增大,推进速度极其缓慢等现象;由于土舱内土体颗粒间力的传递是点对点,使支护压力不能有效施加到开挖面上,极易出现地表沉降超限、塌方等事故.为此,以北京地铁9号线盾构隧道工程为背景,进行砂卵石地层土压平衡盾构隧道施工土体改良试验研究.试验结果表明:采用泡沫十膨润土作为土体改良剂对砂卵石地层土体进行改良是可行的;在土体改良过程中应根据出土量、土压力、盾构推力及刀盘扭矩等参数的控制情况,及时调整土体改良剂的注入时间、注入量等参数;在确保盾构出土量可控的前提下,采用满舱欠压掘进模式可以提高砂卵石地层盾构掘进的效率. 相似文献
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文章针对公路建设项目的水土流失特点,从监测时段、范围、内容、测点布置、工作流程及方法、制度、实施保障等方面入手,对公路水土保持监测技术进行了详细介绍。 相似文献
175.
Monopile-supported offshore wind turbines (OWTs) are dynamically sensitive structures whose fundamental frequencies may be close to those of environmental and turbine-related excitations. The changes in fundamental frequencies caused by pile-soil interaction (PSI) may result in unwanted resonance and serious O&M (Operation and Maintenance) issues, which have been identified as major challenges in the research field. Therefore, a novel model updating framework with an implicit objective function is proposed to monitor both the stiffness and damping variation of the OWT system based on the measured vibration characteristics, which is further verified by laboratory tests. In particular, layered soil was considered in the tests to simulate the practical soil conditions of Chinese seas. Different pile lengths were introduced to consider the long-term PSI effects for rigid piles and slender piles. The results showed that the variation in the fundamental frequency is significantly reduced in layered soil compared with the pure sand scenario. For the OWT systems in layered soil, the variation in foundation stiffness is negatively related to the burial depth under cyclic loading. The proposed model updating framework is proven reliable for support condition monitoring of OWT systems in complicated soil conditions. 相似文献
176.
Suction caissons are one of the most widely used foundation solutions for subsea structures and wind farms. Seismic response of subsea structures is however seldom documented properly, often just treated as a foundation capacity issue applying a quasi-static acceleration and not considering the inertial interaction between the structure and the soil. The more relevant tasks to document are the motions of the unit and the response of the externally connected flowlines and equipment/systems on the unit.Based on a case study located in the Shah Deniz field in the Caspian Sea, model centrifuge tests and numerical modelling were carried out to validate the global response of a 4-caisson supported manifold structure subject to seismic motions in soft clay. The centrifuge tests were carried out at 58 g at the centre for geotechnical modelling at UC Davis. To simulate the soil-structure interaction, a series of non-linear springs defined by kinematic hardening models were used in analyses with the ABAQUS software. This development includes the algorithms for determining the required model parameters. A very good agreement between recorded response from the centrifuge test and calculated response from the FE-analyses was achieved.The development and validation of the soil model presented in this paper is an improvement in design methodology for caisson foundations subjected to earthquake loading. The non-linear soil springs are well suited to incorporate in more detailed structural analyses where an accurate representation of the foundation response is required. The paper also briefly describes how the subsequent earthquake design analyses were performed for the Shah Deniz manifold structures making use of the validated soil spring model and the added value it gave to the project. 相似文献