Excess pore water pressure caused by the installation of jet grouting columns in clay

Techniques including pre-grouting, long pipe roof, and parameter optimization were employed to ensure the safety of loess metro tunnelling under an existing glass building. Their effects were proved through monitoring the settlement of building and surface during tunnelling. Besides, division of settlement monitoring according to processes, a new method, was conducted to control settlement in time. The highest surface settlement after construction was 16 mm only, meeting the requirement. The result indicates that it is practicable to control the tunnelling settlement strictly in extremely difficult geological areas. The settlement regularities were also studied through numerical simulation; their deformation is larger compared with in situ results while their change trends coincide during most processes. Soil excavations cause settlement primarily, accounting for more than 60%. It is suggested that dual slurry pre-grouting and process-based measurement should be employed before each excavation in water-rich loess areas.

Section: Introductionmentioning

confidence: 99%

Tunnelling‐Induced Settlement and Treatment Techniques for a Loess Metro in Xi’an

Lai

et al. 2020

“…(5) Because the physical characteristics of the strata in the Hangzhou area are similar to those in the Shanghai area, the construction of jet grouting with a triple fluid system-twin jet in the Shanghai area should be used for reference. Meanwhile, in the design stage of jet grouting, relevant methods should be used to reasonably estimate the excess pore water pressure and the influence of jet grouting on ground movement [28][29][30][31][32][33][34].…”

Section: Technical Measures and Effectsmentioning

confidence: 99%

Investigation of Water Leakage of Metro Segments Caused by Metro Underpass Structures

Liang

Jin

et al. 2021

Water leaking into metro segments is related directly to the presence of underground water. However, to date, the underground confined water channels formed by metro underpass reinforcement structures have not been considered as causes of the problem. In the present study, based on field investigations and geological data, confined water is identified as the source of segment leakage on Line 5 of Hangzhou Metro in China. It is then hypothesized that the problem stems from an underground confined water channel formed under the reinforced structure of the subway. Numerical simulations predict a settlement difference of 8–10 mm between the reinforcement area and the weak strata, and field monitoring data show this difference to be 8.62 mm. This consistency between the numerical simulations and the field measurements verifies the hypothesis. Finally, given the causes of underground confined water channels, corresponding technical measures such as piecewise secondary grouting are proposed to cut them off and avoid metro-segment leakage. The present research results contribute to the causes of and the laws governing the metro-segment leakage that occurs at subway stations and other reinforced structures.

“…It also shows that the treatment of soft soil subgrade played a vital role in the stability of embankment. Embankment construction or excavation process involves a time-dependent problem due to the dissipation of excess pore water pressure [42,43]. Due to the fact that the pore water pressure indicators were all destroyed because of the carelessness of construction persons during the construction, the time-dependent behavior of this project was not given more focus.…”

Section: Advances In Civil Engineeringmentioning

confidence: 99%

Observed Performance of Highway Embankment over Soft Marine Clay: A Case Study in Wenzhou, China

Bian

Yan

Zhang

2020

This paper presents a case history of observed performance of highway embankment over soft marine clay in Wenzhou, China. During the embankment construction, the changes of ground settlement, ground displacement, and lateral displacement of subsoil with the construction time were monitored and analyzed. The monitoring results indicate that the ground settlement and lateral displacement of subsoil account for about 75% in the process of embankment construction. The measured maximum values of ground settlement, ground displacement, and lateral displacement of subsoil are 37.88 mm, 21.50 mm, and 23.56 mm, respectively. After the completion of the embankment construction, the settlement gradually tended to be stable. It is suggested that the monitoring data of settlement and displacement of embankment are smaller than the design requirements, and the embankment stability is also ensured.