海上风电项目基础沉桩垂直度测量精度控制措施

海上风电具有占地资源少、输电距离短、运行效率高、风力和风能密度大等优势,受到各国重视。在海上风电场建设项目中,打桩船在沉桩作业时极易受到水流影响,水上沉桩垂直度测量精度控制难度较高,需要采取相应的控制措施。本文结合实际的海上风电单桩和四桩项目,探讨了基础沉桩垂直度测量精度控制措施,以最大限度的提高沉桩垂直度测量的精度,提升海上风电项目的建设质量,同时为同类型的海上风电项目的建设提供参考。

深水海域四桩导管架基础沉桩施工关键技术分析

深水海域四桩导管架基础沉桩施工技术在海上风电工程中具有重要应用前景,但是,当前的施工过程中仍然面临适应复杂海况、实现高精度定位、应对多样地质条件等问题。对此,施工方可以从优化沉桩平台设计、提升施工精度以及强化实时监控反馈三方面入手,提高施工效率与质量。在沉桩平台设计上,通过坐底式稳桩平台的创新构造适应深水海域的潮汐和流速变化;在高精度定位方面,利用限位套筒与千斤顶相结合,实现桩体的精确对位,满足高标准的水平和垂直度要求;在实时监控方面,通过GPS定位与反馈控制系统,确保施工中桩体的位置和垂直度始终符合设计要求,达到高质量、安全、高效的施工效果,以期为海上风电项目在复杂海域中的施工提供了有力支持,为后续类似工程提供了可参考的施工技术体系。

海上风电大直径钢管桩基础沉桩施工技术关键要素探究

现阶段,在海上风险项目建设中,大直径钢管桩施工技术是应用比较普遍的技术,该技术也相对成熟和完善。在本次研究过程中,主要分析海上风电大直径钢管桩在基础沉桩施工过程中的关键要素,在实际操作过程中需要加强船舶与稳定架测量定位控制,同时需要从不同环节出发对基础承桩的技术要点科学把握。可以在最大程度上确保海上风电大直径钢管桩沉桩施工效果,同时也为海上风电类似工程项目的施工提供施工参考。

海上多桩风电基础施工中实用在线监测技术

风电基础施工作业中,对桩基础的垂直度、标高、多桩基础的桩间距离要求非常高,测量仪器也较为精密,通常采用手动方式进行精确观测后指导施工。但该操作需暂停施工作业等待测量完成,导致施工效率不高。结合多年的海上施工设计经验及国内外先进实用的测量技术,总结并开发出一套可调激光笔标记的在线测量技术,结合常规的DGPS和倾斜仪等仪器,在保证施工精度的同时,尽可能提高测量效率,确保基础施工主要环节可以连续作业,提高作业效率,减少船舶资源浪费。

谈桩基础在地基处理中的应用

综述了地基处理的原则及方案选择,通过分析地基的宏观特性和目的、了解地基的基础知识,介绍了桩基础的工程应用,对提高地基处理质量具有积极的现实意义。

A new approach for time effect analysis of settlement for single pile based on virtual soil-pile model

A new approach is proposed to analyze the settlement behavior for single pile embedded in layered soils. Firstly, soil layers surrounding pile shaft are simulated by using distributed Voigt model, and finite soil layers under the pile end are assumed to be virtual soil-pile whose cross-section area is the same as that of the pile shaft. Then, by means of Laplace transform and impedance function transfer method to solve the static equilibrium equation of pile, the analytical solution of the displacement impedance fimction at the pile head is derived. Furthermore, the analytical solution of the settlement at the head of single pile is theoretically derived by virtue of convolution theorem. Based on these solutions, the influences of parameters of soil-pile system on the settlement behavior for single pile are analyzed. Also, comparison of the load-settlement response for two well-instrumented field tests in multilayered soils is given to demonstrate the effectiveness and accuracy of the proposed approach. It can be noted that the presented solution can be used to calculate the settlement of single pile for the preliminary design of pile foundation.

Settlement calculation for long-short composite piled raft foundation

The mechanism of long-short composite piled raft foundation was discussed. Assuming the relationship between shear stress and shear strain of the surrounding soil was elasto-plastic, shear displacement method was employed to establish the different explicit relational equations between the load and the displacement at the top of pile in either elastic or elasto-plastic period. Then Mylonakis ＆ Gazetas model was introduced to simulate the interaction between two piles or between piles and soil. Considering the effect of cushion, the flexible coefficients of interaction were provided, With the addition of a relevant program, the settlement calculation for long-short composite piled raft foundation was developed which could be used to account for the interaction of piles, soil and cushion. Finally, the calculation method was used to analyze an engineering example. The calculated value of settlement is 10.2 ram, which is close to the observed value 8.8 mm.

Long-term settlement prediction of high-speed railway bridge pile foundation

The process and characteristics of loading on high-speed railway bridge pile foundation were firstly obtained by means of field research and analysis,and the corresponding loading function was presented.One-dimensional consolidation equation of elastic multilayered soils was then established with single drainage or double drainages under multilevel loading.Moreover,the formulas for calculating effective stress and settlement were derived from the Laplace numerical inversion transform.The three-dimensional composite analysis method of bridge pile group was improved,where the actual load conditions of pile foundation could be simulated,and the consolidation characteristics of soil layers beneath pile were also taken into account.Eventually,a corresponding program named LTPGS was developed to improve the calculation efficiency.The comparison between long-term settlement obtained from the proposed method and the in-situ measurements of pile foundation was illustrated,and a close agreement is obtained.The error between computed and measured results is less than 1 mm,and it gradually reduces with time.It is shown that the proposed method can effectively simulate the long-term settlement of pile foundation and program LTPGS can provide a reliable estimation.

Comparison of seismic capacity/demand ratios of two kinds of foundation schemes of Taizhou Bridge

Pile group foundation and caisson foundation are two common foundation schemes of long-span bridges, and the seismic performances of the two kinds of foundations are different. Taking Taizhou Bridge as an example, which is the first kilometer level three-pylon two-span suspension bridge in the world, two foundation schemes are designed for the middle pylon, and two whole bridge models with two different foundation schemes of the middle pylon are established respectively in this paper. The effects of foundation-soil interaction are simulated by equivalent linear soil springs whose stiffnesses are calculated according to m method. Seismic capacity/demand ratios of the two models are calculated. The following conclusions can be drawn: the weak positions of the two schemes are not the same; if caisson foundation is adopted for the middle pylon, the weak position is the bearing capacity of the middle pylon foundation, while if pile group foundation is adopted for the middle pylon, the weak position is the bearing capacity of the side pylon foundation.

Settlement prediction and behaviour of pile foundations in deep clayey soil deposits

A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.

Settlement monitoring system of pile-group foundation

In order to realize information construction on settlement of pile-group foundation of Sutong Bridge, the monitoring instruments of high-precision micro-pressure sensor and hydrostatic leveling and settlement profiler were integrated synthetically. A set of practical multi-scale monitoring system on settlement of super-large pile-group foundation in deep water was put forward. The reliable settlement results are obtained by means of multi-sensor data fusion. Finite element model of pile-group foundation is established. By analysis of finite element simulated calculation of pile-group foundation, rules of settlement and uneven settlement obtained by monitoring and calculation results are coincident and the absolute error of settlement between them is 4.7 mm. The research shows that it is reasonable and feasible to monitor settlement of pile-group foundation with the system, and it can provide a method for the same type pile-group foundation in deep water.

Finite element analysis on impact of foundation treatment in bridgehead transition section upon bridge piles

In order to decrease relative settlement, foundation treatment plays an extremely important role in bridgehead transition section, especially, the situation of building the bridge piles firstly, and then processing piles. On the basis of engineering practice, the authors analyzed the influence of foundation treatment on bridge piles in bridgehead transition section by finite-element method (FEM). This research has positive significance in predicting displacement of bridge pile, directing construction of foundation treatment, and improving quality of engineering and so forth.