scholarly journals Review on Lateral Stability of Piled Riverine Structures in the Estuaries of Sarawak

2018 ◽  
Vol 7 (3.18) ◽  
pp. 21
Author(s):  
Lee Lin Jye ◽  
Shenbaga R. Kaniraj ◽  
Siti Noor Linda bt Taib ◽  
Fauzan Bin Sahdi
Keyword(s):  
Soft Soil ◽  
Natural State ◽  
Soil Conditions ◽  
Silty Clay ◽  
River Bank ◽  
Soil Movement ◽  
Geotechnical Problem ◽  
Construction Activity ◽  
Lateral Soil Movement ◽  
The Stability

Soft soil conditions with very soft and deep silty clay have constantly endangered the stability of the riverine and estuarine structures in Sarawak. There have been many failures of jetties, wharves and bridges in Sarawak. In many cases of failures, the piles were not designed to resist the lateral movement, unless they were included to stabilize unstable slopes or potential landslides. This practice may be due to reasons such as erroneously judging the river bank as stable in slope stability analysis or simply due to the inexperience of designers. Also, when the river bank approaches the limiting stability in its natural state any construction activity on the river bank could result in lateral soil movement. This paper highlights this important geotechnical problem in Sarawak. Then it presents the details of a few failures of estuarine structures. A review of situations causing lateral loading of piles is then presented. The results of the in-soil and in-pile displacement measurements are shown in this paper and it is found that the computation made to compare between field and 3D modeling is agreeable.  

Field study of pile – prefabricated vertical drain (PVD) interaction in soft clay

2020 ◽  
Vol 57 (3) ◽  
pp. 377-390
Author(s):  
Dongli Zhu ◽  
Buddhima Indraratna ◽  
Harry Poulos ◽  
Cholachat Rujikiatkamjorn
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Negative Skin Friction ◽  
Excess Pore Water Pressure ◽  
Soil Movement ◽  
Lateral Soil Movement ◽  
Compressible Soil ◽  
Excess Pore

Piles and prefabricated vertical drains (PVDs) are two well-established inclusions used by geotechnical practitioners when dealing with soft compressible foundations. Induced movements in highly compressible soil can adversely influence the pile response by inducing additional movements and stresses in the piles. Especially, undesirable soil–pile interaction often leads to the development of excess pore-water pressure during pile installation and negative skin friction caused by the settlement of compressible soil surrounding the piles. Additional drainage by PVDs prior to the installation of a pile could reduce excess pore-water pressure, lateral soil movement, and negative skin friction on the pile. In this paper, full-scale field testing on two trial embankments built on soft soil is reported and the relative behaviour of these two embankments is compared and discussed. Soft soil underneath both embankments was consolidated before one pile was installed at the centre of each embankment. The pore-water pressure, lateral soil movement, surface settlement, and associated strain at the pile shaft were recorded. The pile capacity was tested immediately and 3 h after pile installation. The monitoring and testing results indicated that preconsolidation with PVDs before piling can effectively reduce the excess pore-water pressure, lateral soil movement, and downdrag on the pile.

scholarly journals Feedback of the behaviour of a silo founded on a compressible soil improved by floating stone columns

2018 ◽  
Vol 149 ◽  
pp. 02008
Author(s):  
Ramdane Bahar ◽  
Omar Sadaoui ◽  
Fatma Zohra Yagoub
Keyword(s):  
Soft Soil ◽  
Limit State ◽  
Soil Improvement ◽  
Stone Columns ◽  
Soil Conditions ◽  
Deep Foundations ◽  
The Stability ◽  
Compressible Soil ◽  
The City ◽  
Ongoing Monitoring

The coastal city of Bejaia, located 250 kilometers east of the capital Algiers, Algeria, is characterized by soft soils. The residual grounds encountered on the first 40 meters usually have a low bearing capacity, high compressibility, insufficient strength, and subject to the risk of liquefaction. These unfavorable soil conditions require deep foundations or soil improvement. Since late 1990s, stone columns technique is used to improve the weak soils of the harbor area of the city. A shallow raft foundation on soft soil improved by stone columns was designed for a heavy storage steel silo and two towers. The improvement of 18m depth have not reached the substratum located at 39m depth. The stresses transmitted to the service limit state are variable 73 to 376 kPa. A rigorous and ongoing monitoring of the evolution of loads in the silo and settlements of the soil was carried out during 1400 days that is from the construction of foundations in 2008 to 2012. After the loading of the silo in 2010, settlement occurred affecting the stability of the towers due to excessive differential settlements. Consequently, the towers were inclined and damaged the transporter. This paper presents and discusses the experience feedback of the behavior of these structures. Numerical calculations by finite elements have been carried and the results are compared with the measurements.

Geotechnical Design of Vertically Loaded Hybrid Suction-Gravity Anchors

2017 ◽  
Author(s):  
Majid Hesar ◽  
Raquel Maciel
Keyword(s):  
Development Strategy ◽  
Large Scale ◽  
Soft Soil ◽  
Soil Conditions ◽  
Fe Model ◽  
Silty Clay ◽  
Mooring Lines ◽  
North East ◽  
Pull Out ◽  
Current Events

The Sapinhoá and Lula North-East fields, 300km offshore Rio de Janeiro, Brazil are the two pilot fields of the Pre-salt development strategy. Field architecture consists of satellite wells connected to a spread moored FPSO in each of the fields. Through a design competition Petrobras and Partners selected the de-coupled riser system developed by Subsea 7. In each field two BSRs (Buoy Supporting Risers) anchored at 250m below waterline support the rigid risers on one side and flexible flowlines running to the FPSO on the other. Each BSR displaces close to 10,000t of water and provides a nominal net up thrust of 3,250t. This Paper highlights the engineering challenges and the solution developed for the large-scale foundation anchors that support these massive BSRs in the harsh environment of the Santos Basin in 2140m water depth. Vertically below each corner of the BSR tank an 8m diameter by 18m penetration suction anchor houses the receptacles for the pair of tethers. Tension in the tethers was tuned to optimise the system stiffness (to minimise lateral BSR excursion orbits and avoid clash of risers and FPSO mooring lines) while requiring minimum anchor capacity. Four ballast modules of 150t each sit on top of each suction anchor to provide the remainder of the required uplift resistance. Soil conditions across both fields consist of soft silty clay. A geotechnical FE model of the suction anchor in Abaqus was used to evaluate the interaction of the structure, surrounding soil and trapped water beneath the top cap. The model was used to develop the complete load-displacement curves of the system during the undrained design current events. A consolidation FE model using the Soft Soil model in PLAXIS showed that the hybrid anchor/ballast system under sustained uplift loading is stable throughout the design life for the level of sustained design load. Although the LRFD verification format of suction anchors and gravity anchors are well covered in the design codes, there seems to be a gap in the coverage of this particular type of hybrid anchor. The governing condition was found to be the long term drained pull-out capacity under sustained loading with the assumption of slowly leaking suction port and air evacuation port at the top.

Rig Jacking on Soft Soil Foundations: Improvements in Safety and Speed by Monitoring Leg Loads

1983 ◽  
Vol 105 (2) ◽  
pp. 201-204
Author(s):  
P. F. Ansquer ◽  
S. A. Antalovsky
Keyword(s):  
Continuous Monitoring ◽  
Soft Soil ◽  
Soil Conditions ◽  
Soil Reaction ◽  
Monitoring And Control ◽  
Reaction Forces ◽  
Structural Stresses ◽  
The Stability ◽  
And Control ◽  
Jack Up

The stability of jack-up rigs with spud-cans, particularly during the jacking-up and preloading operations, has always been critical in soft soil conditions. In the offshore areas opened to prospection in Cameroon, unconsolidated clays and silts are frequent, and therefore the need to conduct these critical operations with maximum safety is of utmost importance. The monitoring of soil reactions at the spud-cans and of structural loads at the jack-houses enabled jacking operations to be conducted safely, in an area where other rigs previously encountered severe difficulties (capsizing). Data recorded by instrumentation have shown that leg maneuvering with soil penetrations of up 40 m (131 ft) may induce dangerous overloads to the structure. The continuous monitoring and control of soil reaction forces and structural loads during drilling ensured the safety of the rig. For jacking-down, the monitoring of the loads was necesary to control the structural stresses induced by the legs pulling out. To the authors’ knowledge, no similar measurements have been reported in the past.

scholarly journals Checking the site categorization criteria and amplification factors of the 2021 draft of Eurocode 8 Part 1–1

2021 ◽  
Author(s):  
Roberto Paolucci ◽  
Mauro Aimar ◽  
Andrea Ciancimino ◽  
Marco Dotti ◽  
Sebastiano Foti ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Shear Wave ◽  
Ground Motion ◽  
Shear Wave Velocity ◽  
Soft Soil ◽  
Site Amplification ◽  
Soil Conditions ◽  
Eurocode 8 ◽  
Site Specific ◽  
Amplification Factors

AbstractIn this paper the site categorization criteria and the corresponding site amplification factors proposed in the 2021 draft of Part 1 of Eurocode 8 (2021-draft, CEN/TC250/SC8 Working Draft N1017) are first introduced and compared with the current version of Eurocode 8, as well as with site amplification factors from recent empirical ground motion prediction equations. Afterwards, these values are checked by two approaches. First, a wide dataset of strong motion records is built, where recording stations are classified according to 2021-draft, and the spectral amplifications are empirically estimated computing the site-to-site residuals from regional and global ground motion models for reference rock conditions. Second, a comprehensive parametric numerical study of one-dimensional (1D) site amplification is carried out, based on randomly generated shear-wave velocity profiles, classified according to the new criteria. A reasonably good agreement is found by both approaches. The most relevant discrepancies occur for the shallow soft soil conditions (soil category E) that, owing to the complex interaction of shear wave velocity, soil deposit thickness and frequency range of the excitation, show the largest scatter both in terms of records and of 1D numerical simulations. Furthermore, 1D numerical simulations for soft soil conditions tend to provide lower site amplification factors than 2021-draft, as well as lower than the corresponding site-to-site residuals from records, because of higher impact of non-linear (NL) site effects in the simulations. A site-specific study on NL effects at three KiK-net stations with a significantly large amount of high-intensity recorded ground motions gives support to the 2021-draft NL reduction factors, although the very limited number of recording stations allowing such analysis prevents deriving more general implications. In the presence of such controversial arguments, it is reasonable that a standard should adopt a prudent solution, with a limited reduction of the site amplification factors to account for NL soil response, while leaving the possibility to carry out site-specific estimations of such factors when sufficient information is available to model the ground strain dependency of local soil properties.

scholarly journals Gross Ammonification and Nitrification Rates in Soil Amended with Natural and NH4-Enriched Chabazite Zeolite and Nitrification Inhibitor DMPP

2021 ◽  
Vol 11 (6) ◽  
pp. 2605
Author(s):  
Giacomo Ferretti ◽  
Giulio Galamini ◽  
Evi Deltedesco ◽  
Markus Gorfer ◽  
Jennifer Fritz ◽  
...  
Keyword(s):  
Nitrification Inhibitor ◽  
Natural State ◽  
Silty Clay ◽  
Short Term ◽  
N Losses ◽  
15N Pool Dilution ◽  
Use Efficiency ◽  
Silty Clay Soil ◽  
N Use ◽  
15N Pool Dilution Technique

Using zeolite-rich tuffs for improving soil properties and crop N-use efficiency is becoming popular. However, the mechanistic understanding of their influence on soil N-processes is still poor. This paper aims to shed new light on how natural and NH4+-enriched chabazite zeolites alter short-term N-ammonification and nitrification rates with and without the use of nitrification inhibitor (DMPP). We employed the 15N pool dilution technique to determine short-term gross rates of ammonification and nitrification in a silty-clay soil amended with two typologies of chabazite-rich tuff: (1) at natural state and (2) enriched with NH4+-N from an animal slurry. Archaeal and bacterial amoA, nirS and nosZ genes, N2O-N and CO2-C emissions were also evaluated. The results showed modest short-term effects of chabazite at natural state only on nitrate production rates, which was slightly delayed compared to the unamended soil. On the other hand, the addition of NH4+-enriched chabazite stimulated NH4+-N production, N2O-N emissions, but reduced NO3−-N production and abundance of nirS-nosZ genes. DMPP efficiency in reducing nitrification rates was dependent on N addition but not affected by the two typologies of zeolites tested. The outcomes of this study indicated the good compatibility of both natural and NH4+-enriched chabazite zeolite with DMPP. In particular, the application of NH4+-enriched zeolites with DMPP is recommended to mitigate short-term N losses.

scholarly journals Model Tests on Single Piles Subjected to Lateral Soil Movement

1995 ◽  
Vol 35 (4) ◽  
pp. 85-92 ◽  
Author(s):  
H.G. Poulos ◽  
L.T. Chen ◽  
T.S. Hull
Keyword(s):  
Model Tests ◽  
Soil Movement ◽  
Single Piles ◽  
Lateral Soil Movement

The Stability Control of Soft Soil Foundations of Urban Roads According to the Surface Subsidence Monitoring Data

2013 ◽  
Vol 859 ◽  
pp. 222-227
Author(s):  
Hong Jun Liu ◽  
Jin Hua Tan ◽  
Xue Wen Su ◽  
Hao Wu
Keyword(s):  
Soft Soil ◽  
Stability Control ◽  
Surface Subsidence ◽  
Monitoring Data ◽  
Research Results ◽  
The Road ◽  
Future Design ◽  
Left And Right ◽  
Soil Foundation ◽  
The Stability

Two typical monitoring sections are selected for obtaining the change law of the surface subsidence and the settlement after construction of soft soil foundations, and determining the reasonable unloading time. The research results show that the surface settlement rate is large during the filling stage, the rate decreases after the loading and gradually stabilized. The embankment midline settlement is larger than the settlement of the road shoulder which is concluded from the fact that the subsidence of the middle settlement plate is larger than those of the left and right plate. The surface subsidence rate is less than 5mm per month during the two month before unloading according to the data in the tables. The settlement after construction presumed from the middle plate is more significantly larger than that of left and right sides, hence, as the unloading basis of preloading drainage method in soft soil foundation treatment the settlement after construction which is calculated from the midline monitoring data of the road is appropriate. After 6 months the calculated post-construction settlements of the two sections are in the scope of the design requirement since they decrease with preloading time. The reliable basis is provided for the future design and construction of soft foundation in this area through the research results.

Some difficulties associated with the limit equilibrium method of slices

1983 ◽  
Vol 20 (4) ◽  
pp. 661-672 ◽  
Author(s):  
R. K. H. Ching ◽  
D. G. Fredlund
Keyword(s):  
Slope Stability ◽  
Factor Of Safety ◽  
Limit Equilibrium ◽  
Stability Limit ◽  
Limit Equilibrium Method ◽  
Soil Conditions ◽  
Side Force ◽  
Limit Equilibrium Methods ◽  
Equilibrium Method ◽  
The Stability

Several commonly encountered problems associated with the limit equilibrium methods of slices are discussed. These problems are primarily related to the assumptions used to render the inherently indeterminate analysis determinate. When these problems occur in the stability computations, unreasonable solutions are often obtained. It appears that problems occur mainly in situations where the assumption to render the analysis determinate seriously departs from realistic soil conditions. These problems should not, in general, discourage the use of the method of slices. Example problems are presented to illustrate these difficulties and suggestions are proposed to resolve these problems. Keywords: slope stability, limit equilibrium, method of slices, factor of safety, side force function.

Observations on some basal failures in sheeted excavations

1970 ◽  
Vol 7 (2) ◽  
pp. 136-144 ◽  
Author(s):  
V. Milligan ◽  
K. Y. Lo
Keyword(s):  
Shear Strength ◽  
Ground Water ◽  
Groundwater Level ◽  
Soil Conditions ◽  
Remedial Measures ◽  
Factors Influencing ◽  
Water Head ◽  
The Stability ◽  
Made In

In excavations below groundwater level, instability of the base may result from the inflow of water into the excavation. The most important factors influencing the stability are the ground water and detailed soil conditions at the site.Construction problems encountered in excavations in clay strata, underlain by pervious water bearing layers, are described. The remedial measures adopted in each case are also discussed. From a study of the observations made in the case records, it is suggested that excavation in intact clays may be carried out to depths exceeding that limited by the ratio of t/h = 0.5, where t is the distance from the bottom of the excavation to the top of the water bearing stratum, and h is the water head at the top of the water bearing stratum, provided that the clay is not disturbed during construction so that the shear strength of the clay is preserved.

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