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实测数据统计结果表明,沉管隧道施工期间的沉降占到总沉降的50%以上,而施工期间沉降主要由基础层压缩引起。以舟山沈家门港海底沉管隧道为原型,取纵向30 m建立1∶10缩尺寸模型,试验重点模拟海水环境下注砂基础层形成过程,并研究其在不同回淤条件下的整体压缩过程,评估回淤对压缩的影响。研究结果表明:无回淤条件下砂石基础层整体压缩模量为3.41 MPa,表明沉管隧道基础层的压缩性能较差;夹杂不同浓度的回淤层后,基础层整体压缩模量在1.54~3.89 MPa区间,集中在2.34 MPa附近,约为无回淤条件的0.69倍;回淤起到类似润滑剂的作用,增加了砂石的交错重叠量和垫层整体的塑性,会延长压缩稳定时间,增加基础层的压缩量,放大压缩区域的不均匀性。
The measured data shows that the subsidence during the construction of immersed tunnels accounts for more than 50% of the total settlement, while the subsidence during the construction period is mainly caused by the compression of the foundation layer. Taking the submarine immersed tunnel in Shenjiamen Port of Zhoushan as a prototype, a 1: 10 scale model was established in the vertical direction of 30 m. The experiment focused on the formation process of sand injection foundation under seawater environment and the overall compression process under different back-silting conditions , To evaluate the effect of siltation on compression. The results show that the overall compressive modulus of the foundation layer under backflooding is 3.41 MPa, which indicates that the compressive properties of the foundation layer of the immersed tunnel are poor. After the mixed silt layers with different concentrations, the overall compressive modulus of the foundation layer is 1.54 ~ 3.89 MPa, concentrated in the vicinity of 2.34 MPa, which is about 0.69 times of the condition without back-silting. Back silting plays a similar role of lubricant, which increases the amount of staggered overlap of sandstone and the plasticity of the whole cushion, prolongs the compression stability Time, increase the amount of compression of the base layer, enlarge the non-uniformity of the compression area.