scholarly journals Application of Back-Analysis to Several Test Embankments on Soft Clay Deposits

1986 ◽  
Vol 26 (2) ◽  
pp. 60-72 ◽  
Author(s):  
Katsuhiko Arai ◽  
Hideki Ohta ◽  
Keisuke Kojima ◽  
Masafumi Wakasugi
Keyword(s):  
Soft Clay ◽  
Back Analysis ◽  
Clay Deposits

Ormen Lange Gas Field, Immediate Settlement of Offshore Rock Supports

2007 ◽  
Author(s):  
Guus de Vries ◽  
Joop van der Meer ◽  
Harald Brennodden ◽  
Stein Wendel
Keyword(s):  
Continental Shelf ◽  
Soft Clay ◽  
Back Analysis ◽  
Processing Plant ◽  
Gas Field ◽  
Clay Deposits ◽  
Calculation Results ◽  
The Uk ◽  
Rock Supports ◽  
Norwegian Continental Shelf

Located approximately 120 km offshore, Ormen Lange, with an estimated 400 billion m3 of natural gas, is the second-largest gas discovery on the Norwegian shelf. The water depth is up to 850 meters, making Ormen Lange the first deepwater project on the Norwegian Continental Shelf. The development of Ormen Lange is under shared operatorship between Norsk Hydro and Shell. Ormen Lange’s untreated well stream will be transported to shore in two 120 km long, 30-inch diameter pipelines to a processing plant at Nyhamna, Norway. From there, gas will be exported via a 42” 1200 km sub sea pipeline (Langeled) to Easington at the east coast of the UK. The pipelines have to pass over the Storegga slide edge which rises 200–300 meters toward the continental shelf in very steep slopes, which are also encountered in the nearshore Bjo¨rnsundet area. The uneven and steep seabed conditions require the use of approximately 2.8 million tons of rock to support and stabilize the pipelines. The sea bottom conditions on the Norwegian continental shelf are characterized by many outcrops as well as very soft clay deposits. The immediate settlement of the rock supports during installation form a significant amount of the total required rock volume. In this paper a procedure is presented on how to assess these immediate settlements recognizing four contributing components all being discussed separately. The calculation results are compared to a back-analysis, performed during the execution of the Ormen Lange rockworks, proving the suitability of the calculation method.

Ormen Lange Gas Field: Immediate Settlement of Offshore Rock Supports

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Guus de Vries ◽  
Harald Brennodden ◽  
Joop van der Meer ◽  
Stein Wendel
Keyword(s):  
Continental Shelf ◽  
Soft Clay ◽  
Back Analysis ◽  
Processing Plant ◽  
Gas Field ◽  
Clay Deposits ◽  
Calculation Results ◽  
The Uk ◽  
Rock Supports ◽  
Norwegian Continental Shelf

Located approximately 120 km offshore, Ormen Lange, with an estimated 400×109 m3 of natural gas, is the second-largest gas discovery on the Norwegian shelf. The water depth is up to 850 m, making Ormen Lange the first deepwater project on the Norwegian continental shelf. The development of Ormen Lange is under shared operatorship between Norsk Hydro and Shell. Ormen Lange’s untreated well stream will be transported to shore in two 120 km long, 30 in. diameter pipelines to a processing plant at Nyhamna, Norway. From there, gas will be exported via a 42 in., 1200 km subsea pipeline (Langeled) to Easington at the east coast of the UK. The pipelines have to pass over the Storegga slide edge, which rises 200–300 m toward the continental shelf in very steep slopes, which are also encountered in the nearshore Björnsundet area. The uneven and steep seabed conditions require the use of approximately 2.8×106 tons of rock to support and stabilize the pipelines. The sea bottom conditions on the Norwegian continental shelf are characterized by many outcrops as well as very soft clay deposits. The immediate settlement of the rock supports during installation forms a significant amount of the total required rock volume. In this paper a procedure is presented on how to assess these immediate settlements recognizing four contributing components all being discussed separately. The calculation results are compared with a back analysis, performed during the execution of the Ormen Lange rockworks, proving the suitability of the calculation method.

Analysis and Process Control of the Deformation for Deep Excavation in Soft Clay

2014 ◽  
Vol 580-583 ◽  
pp. 395-400
Author(s):  
Hui Liu ◽  
Wei Bin Li ◽  
Hong Tao Liu
Keyword(s):  
Process Control ◽  
Soft Clay ◽  
Back Analysis ◽  
Control Model ◽  
Prediction System ◽  
Deep Excavation ◽  
Dynamic Prediction

Mechanisms of the distortion of deep excavation in soft clay are recommended on the beginning. Plane FEA method is combined with back-analysis from displacement on this paper to establish a dynamic prediction system of the distortion of deep excavation, which is proved to be viable by practice. Combining with the idea of process control, a process control model of the distortion of deep excavation is established on this paper. It is divided into three parts: advance control, observation and dynamic prediction, process control in the construction.

Soil-Structure Interaction of Heated Pipeline Buried in Soft Clay

2002 ◽  
Author(s):  
Alvaro Maia da Costa ◽  
Carlos de Oliveira Cardoso ◽  
Claudio dos Santos Amaral ◽  
Alejandro Andueza
Keyword(s):  
Challenging Behavior ◽  
Soft Clay ◽  
Back Analysis ◽  
Interaction Model ◽  
Material Behavior ◽  
Soil Reaction ◽  
Inelastic Behavior ◽  
Guanabara Bay ◽  
Structure Interaction ◽  
Non Linear

Heated pipelines buried in soft clay can develop a very challenging behavior. The thermal expansion of the pipelines normally induces buckles, which will be supported by the passive soil reaction. The buckles of the pipelines in soft clay can generate a non-linear inelastic behavior that is an unstable situation named “snap through”. In such situation the pipeline can jump from a configuration of a few centimeters displacement to another of meters displacement. Once the snap through situation has developed, there is the possibility of a local pipeline buckling, causing the pipeline rupture and as a consequence an oil spill. This paper presents the results obtained during the analysis of the rupture of a buried heated pipeline in the Guanabara Bay of Rio de Janeiro, Brazil. A very sophisticated procedure including a simulation of the thermal mechanical interactions between the soil and the pipeline structure was developed for back analysis of the thermal inelastic pipeline buckling. Computer modeling was carried out using the finite element method considering of the non-linear material behavior of the soil and pipeline, and nonlinear geometrical behavior of the pipeline. A cyclic thermal-mechanical soil-pipeline structure interaction model was the challenging aspect of the simulation, that explains the trigger mechanism of the snap through behavior of heated pipelines, which was responsible for the rupture of the pipeline in Guanabara Bay.

scholarly journals Prediction of spudcan penetration resistance profile in stiff-over-soft clays

2016 ◽  
Vol 53 (12) ◽  
pp. 1978-1990 ◽  
Author(s):  
J. Zheng ◽  
M.S. Hossain ◽  
D. Wang
Keyword(s):  
Bearing Capacity ◽  
Soft Clay ◽  
Bottom Layer ◽  
Design Approach ◽  
Rate Dependency ◽  
Soft Clays ◽  
Perfectly Plastic ◽  
Clay Deposits ◽  
Additional Resistance ◽  
Elastic Perfectly Plastic

Spudcan punch-through during installation and preloading process is one of the key concerns for the jack-up industry. This incident occurs in layered deposits, with new design approaches for spudcan penetration in sand-over-clay deposits reported recently. This paper reports a novel design approach for spudcan penetration in stiff-over-soft clay deposits. Large-deformation finite element (LDFE) analyses were carried out using the Coupled Eulerian–Lagrangian (CEL) approach. The clay was modelled using the extended elastic – perfectly plastic Tresca soil model allowing strain softening and rate dependency of the undrained shear strength. A detailed parametric study was undertaken, varying the strength ratio between bottom and top soil layers, the thickness of the top layer relative to the spudcan diameter, and degree of nonhomogeneity of the bottom layer. Existing data from centrifuge model tests were first used to validate the LDFE results, and then the measured and computed datasets were used to develop the formulas in the proposed design approach. The approach accounts for the soil plug in the bottom layer, and the corresponding additional resistance. Where there is the potential for punch-through, the approach provides estimations of the depth and bearing capacity at punch-through, the bearing capacity at the stiff–soft layer interface, and the bearing capacity in the bottom layer. Comparison shows that the punch-through method suggested in ISO standard 19905-1 provides a conservative estimate of the bearing capacity at punch-through, with guidelines provided to improve the method.

Slope instability and valley formation in Canadian soft clay deposits

1986 ◽  
Vol 23 (3) ◽  
pp. 261-270 ◽  
Author(s):  
Guy Lefebvre
Keyword(s):  
Slope Stability ◽  
Soft Clay ◽  
Slope Instability ◽  
Coarse Grained ◽  
Stability Conditions ◽  
Geological Time ◽  
Eastern Canada ◽  
Valley Bottom ◽  
Clay Deposits ◽  
Groundwater Regime

The purposes of the paper are to examine the deepening of valleys in clay deposits of Eastern Canada and in particular to look at the changes in the groundwater regime and slope stability conditions during valley formation. Field observations and laboratory testing indicate that the rate of valley deepening in Champlain clay deposits is of the order of only a few millimetres a year, owing to the low erodibility of the intact clay. The clay banks are, however, more erodible, owing to alteration and fissuration.The stratigraphy of Eastern Canadian clay deposits can be simplified by considering it to be a stratum of low permeabilityconfined between two boundary layers of relatively high permeability, which are the till layer at the base and a weathered crust or coarse-grained layer at the top. As the valley bottom get closer to the bottom till layer, the groundwater regime, and consequently the stability conditions, are modified. During the process of valley formation, the groundwater regime passes through astage where the conditions are rather detrimental to slope stability as it evolves toward conditions that enhance bank stability. Those changes in stability conditions happen over geological time more rapidly or less, depending on clay erodibility. Key words: soft clay, valley formation, slope stability, groundwater, erosion, erodibility.

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