scholarly journals Performance of a Large-Scale Excavation by Bottom-Up Technique in Hangzhou Soft Clay

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Ri-qing Xu ◽  
Yi-hong Zhu ◽  
Pan Ding
Keyword(s):  
Large Scale ◽  
Lateral Displacement ◽  
Soft Soil ◽  
Soft Clay ◽  
Ground Surface ◽  
Diaphragm Wall ◽  
Subway Tunnel ◽  
Control Effect ◽  
Foundation Pit ◽  
Rapid Excavation

This paper studied the excavation of a foundation pit above a running subway tunnel in Hangzhou soft soil. The zoned excavation and top-down construction techniques were adopted to control the deformation caused by foundation pit excavation. The excavation was divided into four parts, named Zone A, B, C, and D. Zone A adopted temporary diagonal bracing, and the control effect of deformation was poor; it was cancelled and changed to rapid excavation and thicker cushion in Zones B, C, and D. During the whole construction process, the lateral displacement and settlement of the diaphragm wall, surrounding ground surface, and building settlement were monitored and analysed. The data showed that the lateral displacement of the diaphragm wall was effectively reduced by the zoned excavation technique, and the maximum lateral displacement value of the diaphragm wall in Zone A was the least; rapid excavation and reduced soil exposure time also could effectively control the deformation, and the lateral displacement of the diaphragm wall in Zone C is less than Zone B and Zone D. The ground settlement is strongly related to the lateral displacement of the diaphragm wall. In order to reduce the surrounding ground and building settlements, efforts should be made to reduce the wall lateral displacement.

Field Performance of a Deep Multi-Strutted Excavation in Hangzhou Soft Clays

2011 ◽  
Vol 243-249 ◽  
pp. 2324-2327
Author(s):  
Hong Wei Ying ◽  
Yong Wen Yang ◽  
Xin Yu Xie
Keyword(s):  
Large Scale ◽  
Soft Soil ◽  
Soft Clay ◽  
Ground Surface ◽  
Field Performance ◽  
Soft Clays ◽  
Soil Clays ◽  
History Of ◽  
Creep Deformations ◽  
Surface Settlements

A case history of a deep multi-strutted soft clay excavation in Hangzhou is presented in this paper. What makes it particular interest is its three characteristics: large scale, deep excavation and very soft clays. The excavated area was about 99750 square meters. The depth of excavation was 12.85 m. 4 m below the ground surface located about 24 m very soft soil clays. Wall deflections and ground settlements were measured and compared with similar case histories worldwide. It was shown that the maximum horizontal deformations of the excavation was very large which this excavation reached to 220 mm. “Creep” deformations occurred apparently during the curing of the bottom slab of the basement. The distributions of the surface settlements seemed to be parabolic, and the settlement influence zone could reach to a distance of more than 2H, whereHis the final excavation depth. The ratio between the maximum ground settlement and the maximum horizontal deformation of the wall is about 0.6.

scholarly journals Numerical Simulation of Soil Displacement and Settlement in Deep Foundation Pit Excavations Near Water

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhongjing Hu ◽  
Qingbiao Wang ◽  
Shuo Yang ◽  
Zhenyue Shi ◽  
Bo Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Yellow River ◽  
Soft Soil ◽  
Ground Surface ◽  
Horizontal Displacement ◽  
Simulation Method ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit

Advancing urbanization in China requires large-scale high-rise construction and underground transportation projects. Consequently, there is an increasing number of deep foundation pits adjacent to water bodies, and accidents occur frequently. This study uses a numerical simulation method to study the stability of the deep foundation pit near water based on the Biot three-dimensional seepage-stress coupling model, with the open-cut section on the south bank of the Jinan Yellow River Tunnel Project as the engineering field test. This indicates the following: (1) the maximum horizontal displacement of the diaphragm wall occurred in the fifth excavation stage, and a horizontal brace effectively controlled the inward horizontal displacement of the foundation pit; (2) considering the effect of seepage in the soft soil foundation, the maximum vertical displacement of the ground surface at each excavation stage occurred adjacent to the underground continuous wall. As the depth of the foundation pit increased, the vertical surface settlement decreases gradually in the direction away from the excavation face; (3) considering the seepage conditions, within each interval of excavation of the foundation pit, the horizontal displacement of the continuous underground wall and ground settlement declined; and (4) the numerical simulation and field monitoring data were in good agreement. Under the conditions of accurate model simplification and parameter selection, numerical simulations can adequately forecast conditions of the actual project.

scholarly journals A Case Study on Field Monitoring Analysis of Deep Foundation Pit in Soft Soils

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Xiaoshuang Zhang ◽  
Xiuchuan Zhang ◽  
Yunshan Han
Keyword(s):  
Lateral Displacement ◽  
Ground Surface ◽  
Field Monitoring ◽  
Diaphragm Wall ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Ground Surface Settlement ◽  
Maximum Lateral Displacement

Field monitoring in the process of excavation of foundation pit is an important measure to reduce the risk. This paper describes a case study of the filed monitoring data during the process of deep foundation pit excavation in soft soil areas. The displacements of the diaphragm wall top were analysed and found that the horizontal displacement showed the convex shape, while the vertical displacement showed the concave shape. Based on the field monitoring data, the deformation mode of lateral displacement of the diaphragm wall belonged to the composite mode. The relationship between maximum lateral displacement and excavation depth showed a strong linear correlation. The horizontal displacements of bracing pillar decreased with the increasing of bracing stiffness, while the effect of bracing stiffness on vertical displacements of bracing pillar could be ignored. The settlement profile computed using the method of Hsieh and Ou was in good agreement with the field observations and better described the development trend of the ground surface settlement. The ratio of the maximum ground surface settlement (δvm) to the maximum lateral displacement of the diaphragm wall (δhm) was in the range of 0.74∼0.88, belonging to the range of 0.5∼1.0 proposed by Hsieh and Ou. This paper provides a reference basis and related guidance for similar projects.

scholarly journals Deformation Characteristics of Raising, Widening of Old Roadway on Soft Soil Foundation

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2117
Author(s):  
Keke Li ◽  
Wenyuan Xu ◽  
Liang Yang
Keyword(s):  
Lateral Displacement ◽  
Soft Soil ◽  
Ground Surface ◽  
Surface Settlement ◽  
Deformation Characteristics ◽  
Construction Methods ◽  
Ground Surface Settlement ◽  
Total Settlement ◽  
Soil Foundation ◽  
Soft Soil Foundation

The deformation characteristics of a raised and widened old Chinese roadway on a soft soil foundation are investigated in this study via finite element numerical simulation. The rules of ground surface settlement, slope foot lateral displacement, and ground surface settlement evolution of the roadbed under three modes (one-time construction of an eight-lane expressway, widened four-lane expressway, and raised/widened four-lane expressway) are compared. The ground surface settlement process of the eight-lane road foundation, which is formed by first widening and then raising the road, is highly complex. The ground surface settlement curve under the old road foundation increases and then decreases. The lateral displacement of the slope foot also interacts with the widening and raising of the eight-lane roadbed foundation. The range of lateral displacement is 70.05, 42.58, 124.81, 104.54 mm. Fifteen years after construction, the total settlement of the raised and widened roadbed is much larger than that of the one built directly. The total settlement values at the center of the two roadbeds are 297.05 and 234.85 mm, respectively. This manuscript provides data support for the reconstruction and expansion of roads on soft soil foundations, for choosing appropriate construction methods to build roads, and for avoiding major road damage, which is of great significance to the construction of road infrastructure in the future.

Study on the Lateral Displacement of Super-Long Pile under a Asymmetrical Surcharge Load in Soft Clay

2014 ◽  
Vol 580-583 ◽  
pp. 733-737
Author(s):  
Qi Li ◽  
Xiao Li Lu
Keyword(s):  
Lateral Displacement ◽  
Soft Soil ◽  
Soft Clay ◽  
Three Dimensional ◽  
Influence Factors ◽  
Major Influence ◽  
Small Contribution ◽  
Practical Engineering ◽  
Surcharge Load ◽  
Building Load

The pile will have a large lateral displacement in soft soil under the role of heaped load. Based on Biot consolidation theory, combined with a certain highway project, a three-dimensional FEM model is established, the process that the soil lateral deformation under heaped load lead to the pile side displacement was simulated. On the ground of the former result, the influence factors for the displacement of pile top and the pile displacement field distribution are analysed. The results show that, the building load area, load grade and the distance from loading area to pile have a major influence on the pile side displacement. On the other hand, the load on pile top have a very small contribution for stability of anti side displacement. The buildings nearby the area of pile foundation should be given attention in practical engineering.

Construction Technique of Cement-Soil Mixing Anchor in Foundation Pit in Soft Soil Area

2011 ◽  
Vol 261-263 ◽  
pp. 1784-1788
Author(s):  
Gan Bin Liu ◽  
Rong Hua Ye ◽  
Li Xu ◽  
Xue Yi Shen
Keyword(s):  
Soft Soil ◽  
Drill Pipe ◽  
Soft Clay ◽  
Mechanical Equipment ◽  
Pullout Capacity ◽  
Foundation Pit ◽  
Construction Technique ◽  
Soil Mixing ◽  
Design Engineers ◽  
Cement Soil

In this paper, the construction technique of a new soil anchor-the cement-soil mixing anchor, which is applicable in the area of soft clay, is introduced. During the construction of the anchor, the drill pipe and blade is served as a reinforced body and formed an anchorage body with the cement-soil body. The material and making, technics parameters, mechanical equipment and construction requirement of the cement-soil mixing anchor are presented firstly. Then, the uplift tests of the cement-soil mixing anchor are carried out, and the ultimate pullout force which is 1.6 times greater than that of the soil nailing in the same condition is obtained. At last, an application of the cement-soil mixing anchor in a foundation pit is given. The test results shown that the application of the cement-soil mixing anchor can reach the expected reinforcement effect. Therefore, this framework can then be used by design engineers to more confidently estimate the pullout capacity of cement-soil mixing anchors under tension loading.

scholarly journals Deformation Law of the Diaphragm Wall during Deep Foundation Pit Construction on Lake and Sea Soft Soil in the Yangtze River Delta

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yuan Mei ◽  
Dongbo Zhou ◽  
Xueyan Wang ◽  
Liangjie Zhao ◽  
Jinxin Shen ◽  
...  
Keyword(s):  
Soft Soil ◽  
Yangtze River Delta ◽  
Diaphragm Wall ◽  
Lateral Deformation ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Deformation Law ◽  
Wall Deformation ◽  
Subway Stations

So far, there have been a large number of diaphragm walls in the Yangtze River Delta as engineering examples of deep foundation pit maintenance structures in subway stations, but there is a lack of systematic research and summary on the deformation characteristics of ground connecting walls. This study aimed to clarify the deformation law of the diaphragm wall during the excavation of a deep foundation pit in a soft soil region. Based on the monitoring data of the diaphragm wall of the deep foundation pit of the Hangzhou metro station, the monitoring data of the deep foundation pits of 15 subway stations in Shanghai and Ningbo cities around Hangzhou were considered. Grouping and classification methods were used to analyze the similarities and differences in the deformation characteristics of the diaphragm wall in the three regions. The results indicate the following: the maximum lateral deformation of the diaphragm wall in Hangzhou increases linearly with the relative depth of the maximum lateral deformation. The maximum lateral deformation of the foundation pit in Hangzhou is 0.072% H∼0.459% H, with a mean of 0.173% H. The wall deformation in Hangzhou varies significantly with the depth of the foundation pit, but the influence of the depth of the foundation pit on the wall deformation is considerably less than that in Shanghai and Ningbo. The corresponding position of the maximum lateral deformation in the excavation depth increases linearly with the excavation depth of the foundation pit, and the corresponding position of the lateral deformation of the diaphragm wall in Shanghai is more affected by the excavation depth of the foundation pit. The lateral deformation of the diaphragm wall increases rapidly in the range of 0 H–0.5 H, and the maximum lateral deformation occurs at 0.5 H–1.1 H.

scholarly journals Investigation of the Axial Force Compensation and Deformation Control Effect of Servo Steel Struts in a Deep Foundation Pit Excavation in Soft Clay

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Honggui Di ◽  
Huiji Guo ◽  
Shunhua Zhou ◽  
Jinming Chen ◽  
Lu Wen
Keyword(s):  
Axial Force ◽  
Soft Soil ◽  
Control Effect ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Deformation Control ◽  
Retaining Structure ◽  
Hydraulic Servo ◽  
Ordinary Steel

This study presents a comparative analysis of the deformation control effect of the hydraulic servo steel struts and ordinary steel struts of a foundation pit based on the measured axial force of the steel struts, lateral wall deflection, and ground surface settlement due to pit excavation. The results indicate that ordinary steel struts installed via axial preloading exhibit a disadvantageous axial force loss with a maximum value equal to 86.7% of the axial preloading force. When compared with ordinary steel struts, the hydraulic servo steel strut exhibits a superior supporting effect. The hydraulic servo steel strut adjusts the axial force in real time based on the deformation of the retaining structure and the axial force of the struts. Thus, the ratio of maximum lateral deflection to the excavation depth of a deep foundation pit in soft soil is less than 0.3%. Concrete struts undergo unsupported exposure during the excavation process, leading to sharply increasing deformation of the retaining structure. Therefore, regarding a foundation pit with strict requirements for deformation control, the use of hydraulic servo steel struts rather than concrete struts is recommended.

Analysis on Deep Excavation in Soft Soil Located on Sloped Bedrock

2012 ◽  
Vol 170-173 ◽  
pp. 13-19
Author(s):  
Shong Loong Chen ◽  
Cheng Tao Ho
Keyword(s):  
Lateral Displacement ◽  
Retaining Wall ◽  
Soft Soil ◽  
Soft Clay ◽  
Observation Data ◽  
Clay Layer ◽  
Deep Excavation ◽  
Element Analysis ◽  
2D Strain ◽  
Significant Difference

Deep excavations in soft-clay layer on sloped bedrock often leads to lateral displacement on retaining structures and uneven settlement due to unbalanced pressure generated from excavation. A construction project for which an excavation was complete in soft clay layer on sloped bedrock in Taipei City was adopted in the study. It is learned from the observation logs of the studied case that a significant difference exists in the lateral displacement of diaphragm wall and settlement between up and down-slope sides of sloped bedrock. Deep excavation is in fact profoundly complicated interaction between excavation strutting and soil. In general practice, the design of excavation is frequently simplified as a 2D strain behavior. However, the actual excavation on sloped bedrock is quite different from 1D or 2D simulation in a symmetric manner. Therefore, 2D finite element analysis program, PLAXIS, is introduced for the analysis on the behaviors of soil clay layer on sloped bedrock in excavation. The result is compared with onsite observation data, including displacement of retaining wall, settlement, axial loads of struts and others. The result of retaining wall displacement analysis is found consistent with the trend derived from onsite observation, which is possible for reference of similar engineering analyses and designs in the future.

scholarly journals ANALISIS DEFLEKSI DAN KAPASITAS LATERAL TIANG TUNGGAL PADA TANAH KOHESIF DENGAN BERBAGAI JENIS KONSISTENSI TANAH

2020 ◽  
Vol 3 (1) ◽  
pp. 81
Author(s):  
Gregory Agustino ◽  
Andryan Suhendra
Keyword(s):  
Lateral Displacement ◽  
Soft Soil ◽  
Soft Clay ◽  
Lateral Force ◽  
Soil Types ◽  
Lateral Capacity ◽  
Lateral Forces ◽  
Curve Method ◽  
Hard Soil ◽  
Hard Soils

There are 2 main elements on a foundation that must be retained from the structure above, the axial force and lateral force. The ability of the foundation to resist lateral forces and deflections that occur due to these forces can be measured by various methods, one of the methods that used in this case is the p-y curve method. In addition to soil types, the lateral capacity and lateral deflection of the pile are also affected by the consistency of the soil itself. Therefore, the writer wants to compare the lateral capacity and lateral displacement of the pile in clay with the consistency of soft, medium, and hard soils. The lateral capacity of medium clay has 100% greater capacity compared to soft clay. The lateral capacity of hard soil increase 600% greater than soft soil. The lateral capacity of the pile also varies with the depth of the pile reviewed. On soft and medium soils with a depth of 5 m the pile has an increase in lateral capacity of 12% to 17% when compared to the lateral capacity at a depth of 10 m. AbstrakPada suatu fondasi terdapat 2 elemen utama yang harus ditahan dari struktur di atasnya, yaitu gaya aksial dan gaya lateral. Kemampuan fondasi dalam menahan gaya lateral dan defleksi yang terjadi akibat gaya tersebut dapat diukur dengan berbagai metode, salah satu metode yang digunakan dalam penulisan ini adalah metode p-y curve. Selain jenis tanah, kapasitas lateral dan defleksi lateral tiang ini juga dipengaruhi oleh konsistensi tanah itu sendiri. Oleh karena itu, dalam penulisan ini penulis hendak membandingkan kapasitas lateral dan perpindahan lateral tiang pada tanah lempung dengan konsistensi tanah lunak, sedang, dan keras. Kapasitas lateral tanah lempung sedang memiliki kapasitas yang lebih besar 100% jika dibandingkan dengan tanah lempung lunak. Sedangkan kapasitas lateral tanah keras memiliki kenaikan kapasitas lateral mencapai 600% jika dibandingkan dengan tanah lunak. Kapasitas lateral tiang ini juga berbeda tiap kedalaman tiang yang ditinjau. Pada tanah lunak dan sedang dengan kedalaman tiang 5 m memiliki kenaikan kapasitas lateral sebesar 12% sampai 17% jika dibandingkan dengan kapasitas lateral pada kedalaman 10 m. 

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