基于FLAC~(3D)的近海淤泥质地层基坑工程变形研究

针对深厚淤泥质软土基坑变形过大的问题,采用了水泥土搅拌桩与地下连续墙组合支护方案,为了解该支护方案中地下连续墙的变形特征,利用FLAC~(3D)数值模拟软件对深圳地铁十号线地铁停车场深基坑进行分析。结果表明:模拟结果与实测数据拟合较好,预测开挖完成后基坑周围土体最终沉降为22.91 mm,小于警戒值。在水泥土搅拌桩支护条件下,除按原工况1 200 mm厚地连墙条件外,分别模拟了1 100 mm、1 000 mm、900 mm、800 mm、700 mm不同地下连续墙厚度条件下的变形情况,第一层开挖时各条件下土体沉降相差不大。随着开挖的进行,沉降值开始发生变化,土体沉降值最小为47.33 mm,发生在1 100 mm厚条件下,最大为93.85 mm发生在700 mm厚条件下。地下连续墙水平变形最大值均发生在距墙顶15 m处左右。在700 mm条件下变形值最大达到了42.58 mm,1 100 mm条件下最小,其值为25.71 mm。因此,该深基坑工程在水泥土搅拌桩支护成槽条件下,可适当减少地连墙厚度,采用1 100 mm厚地连墙能保证基坑安全的前提下降低造价。

FLAC_3D -based study on deformation of muddy stratum foundation pit

Aiming at the problem of larger deformation of deep muddy soft soil foundation pit，the supporting scheme combined with both soil-cement mixed pile and underground diaphragm wall is adopted，for which the deep foundation pit for the parking lot of Shenzhen Metro Line 10 is analyzed herein with FLAC3D numerical simulation software，so as to find out the deformation characteristics of the underground diaphragm wall in the supporting scheme. The result shows that the simulated results is better coincided with that of the measured data，which predicts that the final settlement of the pit surrounding soil mass is 22. 91 mm after the excavation and less than the relevant warning value. Under the condition with the supporting of soil-cement mixed pile，the deformations under the different thicknesses of the underground diaphragm wall，i. e. 1 100 mm，1 000 mm，900 mm，800 mm and 700 mm are simulated respectively except the original condition of the underground diaphragm wall thickness of 1 200 mm; for which no large differences of soil mass settlement are there under all the conditions concerned during the first layer excavation. Along with the excavation，the change of the settlement value occurs; for which the minimum settlement of soil mass is 47. 33 mm and occurs on the condition of the thickness of 1 100 mm，while the maximum value is 93. 85 mm and occurs on the condition of the thickness of 700 mm. All the maximum values of the horizontal deformations of the underground diaphragm wall occur at the distances of about 15m to the wall crest. Under the condition of the thickness of 700 mm，the maximum deformation value reaches to 42. 58 mm，while the minimum deformation value occurs on the condition of the thickness of 1 100 mm and is 25. 71 mm. Therefore，under the trenching condition supported with soil-cement mixed pile for this deep foundation pit project，the thickness of the underground diaphragm wall can be appropriately reduced，that is to say，under the premise of ensuring the safety of the foundation pit through adopting the underground diaphragm wall with the thickness of 1 100 mm，the construction cast can be decreased.