Figure - available from: Geotechnical and Geological Engineering
This content is subject to copyright. Terms and conditions apply.
Stages of foundation pit construction.a Excavation depth is 2.5 m, and the concrete support was erected;b Excavation depth is 5.5 m;c Excavation depth is 9 m, and steel support was erected;d Excavation depth is 11.5 m;e Excavation depth is 14 m, and the last steel support was erected;f Excavation depth is 17.5 m
Source publication
Trench cutting re-mixing deep wall method (TRD) is an increasingly common method for building waterproof curtains in deep foundation pits. By combining numerical simulations and field monitoring, this study investigated the deformation characteristics of the TRD cement soil mixing wall and soil surrounding the foundation pit. By considering the eff...
Citations
... In municipal construction engineering, deep excavation is a comprehensive geotechnical engineering problem (Mandala et al. 2023;Deliveris et al. 2022). It involves not only researches on the deformation characteristics of the excavation bracing system (Liu and Liu 2012;Xu et al. 2015;Liu et al. 2019aLiu et al. , 2022, but also studies on the responses of adjacent ground and preexisting structures (Dong et al. 2016;Lim and Ou 2018;Li et al. 2018;Liu et al. 2019b;Guo et al. 2021aGuo et al. , 2023. The stability of the deep excavation as well as the potential influence of excavation disturbance on adjacent structures in urban areas are the key contents of deep excavation engineering (Sun Abstract This paper reports a typical case history of deep braced excavation for constructing the main bridge cushion cap of the Yangwan River Bridge to explore the excavation performance under embankment surcharge load. ...
near-embankment side than the far-embankment side. The responses on the near-embankment side are more sensitive to the embankment-excavation distance and the river level. However, the effects of these parameters diminish greatly when the embankment-excavation distance exceeds 1.5 times the excavation depth. The excavation bottom sealing measures can reduce the retaining structure deformation, and effectively restrain basal heave. This restraint weakens as the excavation bottom sealing thickness exceeds 1 m.
... Numerous research works in the literature take the time to explain the use features of the DSM process in the improvement of the bearing capacity of clayey soils [21][22][23][24], supporting struc-tural foundations [25][26][27][28] or waterproofing [29][30][31][32][33]. However, the effect of soil inclusions not mixed with cement is rarely mentioned [15,16,17,19,20,34,35]. ...
The Deep Soil Mixing (DSM) material is a cementitious composite consisting of a well-mixed soil/cement matrix and may contain unmixed soil inclusions and possibly gravel. To obtain a 3D reconstruction of a DSM specimen structure, a destructive method was investigated, as an alternative to X-Ray Computed Tomography scans. The proposed method is based on image analysis and photographs of few millimeters thickness slices of a specimen. A detailed morphological description of inclusions, including volume fraction, shape, size distribution and spatial arrangement using common image analysis and CAD softwares preceded the validation of the 3D destructive method by the non destructive X-ray CT based on 3 criteria (volume fraction, size distribution and shadow zone area). Compared to 1D and 2D basic methods found in the literature, the 3D developed method prevented biases linked to the external surface estimation of inclusions’ volume fraction. Next, to improve the experimental procedure, an extended methodology was established for estimating the inclusions volume fractions. Such method relies on a database of 3D reconstructed inclusion shapes and on the optimization of the sawing thickness. The aim consisted in the obtaining of unbiased estimates of the volume fractions with fewer cuts, between 4 and 18 instead of 50–60, which made such method as a low-cost, practical and accurate procedure. Finally, the 3D mesh generated by the 3D destructive method was used in numerical approach to propose, as an example, a successful hydromechanical numerical simulation of the DSM material response. Furthermore, a machine learning framework using the 2D slices of specimens produced during the application of the 3D destructive method, was proposed to generate various realistic 3D shapes instead of the usual spherical shape for inclusions, which will allow testing high number of meso-structures in numerical simulation.
Under watery and weak stratum conditions, deformation regulations and instability conditions of each stage of a deep foundation pit construction for a subway station become more complicated than those in more common areas, thus causing major security problems. This study used and examined open-cut deep foundation pit engineering of a subway station under construction and considered watery and weak stratum characteristics. The finite difference method was used to simulate the support structures of the deep foundation pit excavation process while considering the station main body structure, initial ground stress, construction process, and stratum physical and mechanical parameters. Meanwhile, the actual construction process was monitored and ground settlement, enclosure structure horizontal displacement, supporting axial force, and influence of engineering drainage analyzed. This study found that the monitoring stability value of the enclosure structure was slightly less than the predicted value from numerical calculations. The changing trends of both monitored and simulated values were in accord with theoretical analysis. These results showed that ground settlement grew rapidly in the middle excavation stage. The maximum horizontal displacement of the enclosure wall occurred at the upper part of about 1/3rd depth of the foundation pit. The supporting effect of steel supports was better than that of reinforced concrete support. After the drainage was stable, the final average ground settlement value of monitoring points caused by foundation pit drainage was 7.69 mm. The enclosure structure and inside support structure of the station deep foundation pit could guarantee the stability of surrounding rock during construction. These results provided guidance for the design optimization and construction of similar engineering projects.
In the process of excavating the deep pit, due to the change in groundwater level, will inevitably cause uneven settlement of the surrounding buildings. To prevent such uneven settlement and to protect the safety of surrounding buildings, recharging methods are often used in the project. In this paper, with the engineering example, the finite element software is used to simulate the deep excavation dewatering and recharge process, and the influence of different recharge volumes, different lengths of recharge wells, and recharge wells with different positions on the settlement of buildings is studied. The results show that the greater the amount of recharge, the better the control effect on building settlement, but the excessive amount of recharge will lead to the uplift of the surrounding soil of the building. With the same amount of recharge, the longer the length of the recharge well, the smaller the settlement of the building. The recharging well can restore the water level lost at the building due to dewatering. The larger the amount of recharge, the longer the length of the recharging well and the more the water level is restored. When the recharging well is between the building and the dewatering well, the settlement control effect of the recharging well is the best.
with the development of the times, the expansion of urban scale and the development and utilization of underground space, the building foundation pit is developing in the direction of "large and deep". The traditional deep foundation pit support construction technology can no longer meet people's needs for the construction of deep and large foundation pits, thus deriving a new construction technology TRD construction method, which has a wide range of application, guaranteed wall quality and depth, and high construction efficiency. This construction method has been born for more than 30 years and has been popularized and applied in China for more than 10 years. This paper will briefly introduce the trd method from the aspects of its development, characteristics and academic research process of related applications. It is not difficult to see from the relevant research that the trd method has broad application prospects in China.
