scholarly journals An Investigation of Time-Dependent Deformation Characteristics of Soft Dredger Fill

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Wanying Wang ◽  
Qingzi Luo ◽  
Bingxiang Yuan ◽  
Xiaoping Chen
Keyword(s):  
Soft Clay ◽  
Deformation Characteristics ◽  
Soft Clays ◽  
Creep Coefficient ◽  
Creep Characteristics ◽  
Deformation Features ◽  
Consolidation Coefficient ◽  
Geometric Confinement ◽  
Dredger Fill ◽  
Two Parameters

The creep characteristics of soft clays have been studied for decades. However, the lateral deformation of soils is not allowed during the commonly used one-dimensional consolidation tests, which cannot describe the real deformation features of soils in practice. On the other hand, the influence of drainage distance on the mechanical properties of soil is still controversial, classified as hypothesis A and hypothesis B. For a better understanding of deformation characteristics of soft clay, especially which in long-terms, a series of conventional oedometer tests as well as novel geometric confined consolidation tests was conducted on soft dredger fill. The results show that the secondary consolidation coefficient of the soil sample Cα would increase firstly, followed by a small decrease with the increase of consolidation pressure generally. Cα would decrease with the consolidation time and also be reduced by preloading. The strain at the completion of primary consolidation would increase with the drainage distance, but the Cα would be affected little. Both compression index Cc and Cα of soft clay would reduce after preconsolidation, in which two parameters show an approximate linear relationship. The creep coefficient of soft clay under the geometric confinement Cαε k is larger than that under the oedometer test Cαε. However, the trends of the relationship between the creep coefficient and loading are consistent regardless of the confinement conditions.

scholarly journals Experimental and Analytical Study on Creep Characteristics of Box Section Bamboo-Steel Composite Columns under Long-Term Loading

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 983
Author(s):  
Shixu Wu ◽  
Keting Tong ◽  
Jianmin Wang ◽  
Yushun Li
Keyword(s):  
Load Level ◽  
Experimental Results ◽  
Creep Model ◽  
Composite Column ◽  
Composite Columns ◽  
Creep Coefficient ◽  
Creep Characteristics ◽  
Section Size ◽  
Steel Composite

To expand the application of bamboo as a building material, a new type of box section composite column that combined bamboo and steel was considered in this paper. The creep characteristics of eight bamboo-steel composite columns with different parameters were tested to evaluate the effects of load level, section size and interface type under long-term loading. Then, the deformation development of the composite column under long-term loading was observed and analyzed. In addition, the creep-time relationship curve and the creep coefficient were created. Furthermore, the creep model of the composite column was proposed based on the relationship between the creep of the composite column and the creep of bamboo, and the calculated value of creep was compared with the experimental value. The experimental results showed that the creep development of the composite column was fast at first, and then became stable after about 90 days. The creep characteristics were mainly affected by long-term load level and section size. The creep coefficient was between 0.160 and 0.190. Moreover, the creep model proposed in this paper was applicable to predict the creep development of bamboo-steel composite columns. The calculation results were in good agreement with the experimental results.

scholarly journals Assessing the undrained strength of very soft clays in the SPT

2021 ◽  
Vol 44 (4) ◽  
pp. 1-6
Author(s):  
Francisco Lopes ◽  
Osvangivaldo Oliveira ◽  
Marcio Almeida
Keyword(s):  
Standard Procedure ◽  
Soft Clay ◽  
Test Procedure ◽  
State Theory ◽  
Technical Note ◽  
Construction Site ◽  
Soft Clays ◽  
Design Engineers ◽  
Present Information ◽  
Undrained Strength

The log of a SPT in very soft clay may simply indicate a zero blow-count, or present information on the penetration – under self-weight – of the composition (sampler, rods and hammer) as recommended by some standards. The second type of information is often disregarded by design engineers due to the lack of a standard procedure for measuring these penetrations or because the test is regarded as not sensitive enough to give an indication on the undrained shear strength of soft clays. The penetration under the composition’s selfweight, however, can indicate the magnitude of Su, which, along with other more specific and sensitive tests, can help in assessing the spatial distribution of clay consistency in a large deposit. A proposed test procedure and interpretation had been given in an earlier technical note. This note presents an extended formulation and an evaluation of Su via the SPT at a construction site in Rio de Janeiro, including comparisons with results of piezocone and vane tests. The values of Su obtained with the SPT lie between the profiles given by vane tests, corrected by Plasticity Index, and the Critical State Theory, the latter representing a lower bound to the clay strength.

Behaviour of friction piles in soft sensitive clays

1980 ◽  
Vol 17 (2) ◽  
pp. 203-224 ◽  
Author(s):  
R. Blanchet ◽  
F. Tavenas ◽  
R. Garneau
Keyword(s):  
Precast Concrete ◽  
Soft Clay ◽  
Load Test ◽  
Pile Groups ◽  
Test Program ◽  
Shear Creep ◽  
Soft Clays ◽  
The North ◽  
Effective Stress Analysis

During the construction of heavy structures, such as bridges and overpasses, on soft clays on the north shore of the St. Lawrence Valley, a detailed load test program on friction piles was performed to establish the characteristics of the most suitable type of pile and to study its long-term behaviour. Three types of piles, timber, steel pipe with closed end, and precast concrete Herkules H-420 piles, were tested. Four timber piles driven in a group and submitted to a 712 kN load served to study the long-term settlement of a small group of piles. Three deep settlement gauges were installed in the centre of this group for measuring settlements in clay at various depths.This test program was completed by the instrumentation of two bridge piers in order to verify the behaviour of larger groups of piles.The paper presents the results of the test piles, the long-term behaviour (4 years) of the bridge pier foundations resting on friction piles in soft clay, and the interpretation of the results.This study shows that the pore pressures induced by pile driving are related to the pre-consolidation of the clay and that they are much larger for tapered piles. It is demonstrated that the effective stress analysis method proposed in 1976 by Meyerhof determines adequately the ultimate pile bearing capacity, but that the effect of the timber pile taper doubles the skin friction.The settlement analysis of pile groups shows that settlements are due to the reconsolidation of the clay and shear creep deformations in the clay close to the pile wall.

Uncertainty of One-Dimensional Consolidation of Multi-Layered Soft Clay Soils

2011 ◽  
Vol 250-253 ◽  
pp. 1838-1841
Author(s):  
Xiao Yong Li
Keyword(s):  
Soft Clay ◽  
Compression Modulus ◽  
Probability Characteristic ◽  
Coefficient Of Consolidation ◽  
One Dimensional ◽  
The Monte Carlo Method ◽  
Consolidation Coefficient ◽  
Characteristic Values ◽  
Consolidation Degree ◽  
Substantial Degree

The measured coefficient of consolidation can have a substantial degree of variation even in a uniform clay layer. The probability characteristic values for such parameters as consolidation coefficient and compression modulus are analyzed from local engineering data. This paper, through a probabilistic analysis, examines the variability of one-dimensional consolidation solutions. The multilayer models are evaluated. Then the Monte Carlo method is used to develop solutions for one dimensional consolidation. It identified the influence of the parameter uncertainty on the probability characteristic of the consolidation degree. The uncertainty of consolidation coefficient has a great impact on the probabilistic characteristics of the consolidation degree, but for compression modulus it is opposite true. It proposed a simplification analysis method that considers only the uncertainty of consolidation coefficient without consideration of the uncertainty of compression modulus, and its erroneous precision can meet the engineering requirements.

Effective stress paths and yielding in soft clays below embankments

1985 ◽  
Vol 22 (3) ◽  
pp. 357-374 ◽  
Author(s):  
D. J. Folkes ◽  
J. H. A. Crooks
Keyword(s):  
Pore Water ◽  
Effective Stress ◽  
Strain Softening ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Clay ◽  
Stress Path ◽  
Excess Pore Water Pressure ◽  
Soft Clays ◽  
Effective Stress Path

Current methods of predicting the response of soft clays to surface loading are often unsuccessful because the assumed constitutive relationships, including effective stress path behaviour, are incorrect. In particular, the transition from small-strain to large-strain behaviour (i.e. yielding) is frequently not taken into account. Recent laboratory testing has demonstrated that the behaviour of soft clays is largely controlled by yielding. The locus of effective stress states causing yield is known as the yield envelope (YE).The effective stress paths (ESP's) in soft clay foundations below the centre of six fills were determined from computed total stresses and measured pore-water pressures. Yield behaviour is clearly indicated by ESP shapes. The yield envelopes inferred from analyses of field data are similar to those obtained from laboratory testing. Effective stress path shapes vary widely, depending on a variety of factors, including imposed stress level, rate of construction, and boundary drainage conditions. This finding contradicts an earlier conclusion that soft clay behaviour can be characterized by a single ESP. Because of the wide range of possible ESP shapes, the parameters [Formula: see text] does not provide an adequate basis for determining the effective stress state in a soft clay.The ESP/YE analyses indicate that yield can occur either during loading or during excess pore-water pressure dissipation following completion of loading. Yield of sensitive soils during loading is usually followed by strain softening. However, in some soils, dilatant behaviour appears to occur. Yield during dissipation of excess pore-water pressure is characterized by a dramatic change in cv and increased compressibility. Key words: soft clay, yield, effective stress paths, field behaviour, strain softening, rate of consolidation.

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.

Experimental Study on Creep Characteristics of Coal under Uniaxial Compression

2012 ◽  
Vol 594-597 ◽  
pp. 290-293
Author(s):  
Yong Jie Yang ◽  
Ming Fu Guo ◽  
Dong Wei Chen
Keyword(s):  
Mechanical Test ◽  
Test System ◽  
Load Level ◽  
Creep Failure ◽  
Deep Mine ◽  
Creep Coefficient ◽  
Multi Stage ◽  
Creep Characteristics ◽  
Cubic Polynomial ◽  
Rock Mechanical Test

Generally surrounding rocks of deep mine show the typical creep characteristics and the multi stage loading creep test of coal was carried out by MTS815 rock mechanical test system in this paper. Compared to the creep coefficient of other rocks, creep coefficient of coal is relatively small. Coal creep failure changes obviously when load level is higher than the threshold stress. The constitutive characteristics of creep failure of coal can be fitted preferably by the Cubic Polynomial.

Cyclic Loading Histories for Seismic Experimentation on Structural Components

1996 ◽  
Vol 12 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Helmut Krawinkler
Keyword(s):  
Inelastic Deformation ◽  
Cyclic Load ◽  
Deformation Characteristics ◽  
Frequency Content ◽  
Structural Components ◽  
Seismic Demands ◽  
Critical Issues ◽  
Load Tests ◽  
Two Parameters ◽  
Selection Of

In order to utilize results obtained from quasi-static cyclic load tests on structural components for a general performance evaluation, the need exists to establish loading histories that capture critical issues of component capacity as well as seismic demands. In inelastic seismic problems capacity and demands cannot be separated since one may strongly depend on the other. Because of cumulative damage issues the capacity depends on the number of inelastic excursions and the magnitude of each excursion (not just the largest one). These two parameters depend on the frequency content of the ground motion, the period(s) of the structure, and the strength and inelastic deformation characteristics of the structure. The paper presents procedures how these characteristics can be considered in the selection of suitable loading histories.

Comparative Study of Different Form of Asphalt Mixture Viscoelastic Rheological Model

2012 ◽  
Vol 204-208 ◽  
pp. 1773-1776
Author(s):  
You Yun Li ◽  
Xin Bo Zheng ◽  
Zhen Yi
Keyword(s):  
Experimental Data ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Deformation Characteristics ◽  
Rheological Models ◽  
Advantages And Disadvantages ◽  
Proposed Model ◽  
Creep Characteristics ◽  
The Common

In this paper, based on the essential attribute of the asphalt mixture, the characteristics of the asphalt mixture creep deformation were analyzed. With the comparison of the theoretical and experimental results, the advantages and disadvantages of the common rheological models used as the reaction of asphalt mixture creep characteristics were studied. The characteristics of of the asphalt mixture deformation have been analyzed. For the accurate response of nonlinear viscous elasticity model of asphalt mixtures must be a reasonable combination of the characterization of deformation characteristics of various components, this paper reveals the rheological deformation of asphalt mixture of components and parts of correspondence with the proper models. Finally, the experimental data were given to verify the correctness of the proposed model.

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.

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