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1.
Remolded Undrained Strength of Soils 总被引:12,自引:6,他引:12
1 .IntroductionManyresearchershaveillustratedthatthesoftmarineclayeysoilsgenerallyshowtheoverconsoli dationratiobeinglargerthanunity ,althoughthesitegeologyindicatesnormalconsolidation (e .g .,Zhangetal.,1 995;HongandTsuchida ,1 999) .Burland (1 990 )illustratedthatthem… 相似文献
2.
Although extensive research has been performed on the mechanical properties of cement-stabilized clays, quite a few attempts have been made on the compression behavior of remolded cement-admixed clays. The results from oedometer tests have been discussed to investigate the compressibility of remolded cement-admixed clays, taking into consideration cement amount and curing time. The findings show that the difference in shape and position of compression curves is attributed to cement amount and curing time. Most compression index (Cc) values of remolded cement-admixed clays are greater than those of untreated clay due to the presence of remolded yield stress σ′yr that is closely related to initial water content and clay fabric. Based on the obtained test data, the relationships of Cc vs. e0, Cc vs. w0, Cc vs. e1, Cc vs. eyr, and σ′yr vs. eyr are preliminarily discussed and quantitatively established. Especially, an important divergence of void index Iv at effective stress σ′v less than remolded yield stress σ′yr can be observed at different cement amounts and curing durations. Being independent on cement amount, curing time, and initial state of soil, an excellent convergence occurs at stress σ′v greater than yield stress σ′yr. The normalized compression curves of Iv vs. σ′v at σ′v?>?σ′y can be expressed by a unique line that agrees well with intrinsic compression line (ICL) and extended ICL. 相似文献
3.
Liang Wang Wei Zhu Jian Xie Lei Li Chunlei Zhang 《Marine Georesources & Geotechnology》2013,31(6):556-566
The shear strength properties of sediments are relevant to many practical problems, including those related to predicting the bearing capacity of the man-made crust lying over dredged disposal sites and those associated with estimating the erosion resistance and the bearing capacity of sediments. In this study, an experimental apparatus and method is developed for sedimentation. This apparatus consists of a settling column, pore measurement apparatus, shear vane apparatus, and multilayer extraction sampling apparatus. The change regulation of interface height, density, excess pore pressure, peak undrained shear strength, residual undrained shear strength, and sensitivity varies before and after the excess pore pressure dissipates to zero in the self-weight consolidation stage. The higher the water content, the greater the particle segregation degree. Particles are mainly segregated in the settling stage, and they are not segregated further in the self-weight consolidation stage. Before excess pore pressure dissipates to zero in the self-weight consolidation stage, shear strength is related to water content, effective stress, and the formed structure of sediments. After excess pore pressure dissipates to zero, peak undrained shear strength is mainly associated with the structure (thixotropy) of sediments. Residual undrained shear strength increases because of the slight decrease in water content. The mechanisms of thixotropy can be expressed as the increase in the original and curing cohesions of sediments with time as determined from microscopic aspects. 相似文献
4.
Dongseop Lee Sangwoo Park Timothy D. Stark Younguk Kim 《Marine Georesources & Geotechnology》2013,31(4):348-359
Use of Terzaghi's one-dimensional consolidation theory is not suitable for consolidation of highly deformable soft clays such as dredged soils. To model this condition, it is necessary to consider non-linear finite strain consolidation behavior, i.e., changes in compressibility and permeability with increasing stress. A one-dimensional non-linear finite strain numerical model, Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill (PSDDF), has been used to predict the stress-dependent settlement of fine-grained dredged materials. In this paper, two case studies of using PSDDF are discussed to illustrate the applicability and accuracy of PSDDF. The first case study involves PSDDF simulations of laboratory-phased placement of a marine clay dredged from Busan, Korea. PSDDF results are in good agreement with the corresponding results of the laboratory large strain consolidation tests. The other involves estimating the service life of the Craney Island Dredged Material Management Area near Norfolk, Virginia, in the United States. The excellent agreement between measured and calculated values shows that PSDDF is a reliable tool for predicting settlement of dredged material. 相似文献
5.
Jacques Locat Homa Lee Robert Kayen Ken Israel Marie-Claude Savoie Éric Boulanger 《Marine Georesources & Geotechnology》2013,31(2):111-135
As part of the STRATAFORM project, a series of cores were obtained from the Eel River Margin area of Eureka, California. The geotechnical analysis of intact specimens and of reconstituted samples provides some insight on the development of shear strength with burial. The results show the effect of bioturbation in the early part of the lifetime of a sediment. SEDCON tests were used to proposed various relationships which help predict the changes in density, liquidity index, and strength as a function of depth. These relationships are found useful from near the water sediment-interface down to a depth of at least 400 m in the sediment column. 相似文献
6.
G.-G. Yea 《Marine Georesources & Geotechnology》2013,31(1):76-90
The behaviors of the marine sedimentary ground improved by sand compaction pile (SCP) method are analyzed. To do this, the results of upheaval characteristics of the sea floor, undrained shear strength, and horizontal consolidation coefficient (consolidation) are investigated. Due to SCP installation on ground, as thickness of a soft clay layer increases, upheaval height increases and upheaval angle decreases. Undrained shear strength of disturbed ground due to SCP construction decreases in early stage after completion of construction, but it shows a trend of recovering as months elapse. As the result of piezocone penetration dissipation tests, consolidation delay phenomenon by the disturbance due to SCP installation clearly is identified and its degree is dependent on the replacement area ratio of SCP and the location of ground. 相似文献
7.
Dongxing Wang Nor Edine Abriak Rachid Zentar 《Marine Georesources & Geotechnology》2017,35(4):472-480
The dredged marine sediments are classified as waste and how to deal with such kind of abandoned materials is a great challenge. The main objective of this experimental work is to provide a novel way to reuse dredged sediment as filling materials in road section. The laboratory dewatering test is performed to model the in situ evaporation and dewatering process of untreated and treated sediment with chemical binder. The impact of binder amount and time is discussed on the change of water content influenced by evaporation. To valorize dredged sediments as roadbed materials, a hydraulic binder is incorporated to investigate its effect on the bearing capacity and strength performance. The suitability of stabilized sediment is assessed based on the obtained mechanical results followed by a detailed discussion on the in situ test roads. 相似文献
8.
Palanidoss Subramaniam Mohanachandra Menon Sreenadh Subhadeep Banerjee 《Marine Georesources & Geotechnology》2016,34(7):603-616
The present article discusses the stress–strain behavior and critical state parameters of the dredged Chennai marine clay stabilized with low cement content (2.5–10%). A series of one-dimensional consolidation tests and consolidated undrained tri-axial tests are performed on the cement stabilized dredged Chennai marine clay to evaluate the critical state parameters (λ, κ, M, Г, N) for varying cement contents and curing days. The results show that the slope of the critical state line M increases with an increase in the cement content. The parameter λ for the treated marine clay increases up to a cement content of 7.5% followed by a reduction. The parameter κ decreases with the addition of cement content. Finally, empirical formulations are proposed to predict the critical state parameters as the functions of the cement's contents and curing days. 相似文献
9.
The properties of sands pertaining to shear strength have been studied extensively by plane strain and triaxial tests for relative densities above 40%. Unfortunately, properties of sand have not been comprehensively studied for relative density below 40%. An experimental investigation of the shear strength of Jumunjin sand was carried out using a plane strain, triaxial and direct shear apparatus according to relative density ranges from 0 to 100%. Because of the complexity of the shear tests on coarse materials, correlations were developed that would be useful for practical purposes. This article presents a comparison of strength properties' results and their correlation with relative density. 相似文献
10.
Yu Xiaodong Yan Shuwang Sun Wanhe
Postgraduate Student Tianjin University Tianjin Professor Tianjin University Tianjin Senior Engineer Tianjin Port Engineering Institute Tianjin 《中国海洋工程》1997,(2)
At pesent,it is very popular to estimate pile bearing capacity by use of empirical formula andphysical indexes of soil provided in the design codes for civil construction in China.This paper attempts toapply mechanical indexes of soil and semi-empirical formulas,which are based on soil mechanical theoriesand were summarized and presented by Meyerhof in 1976,to calculate the axial pile bearing capacity.Lo-ading test results of 24 single piles in Tianjin area have been collected and compared with the proposed cal-ulation approach. 相似文献
11.
For decades, various well-known empirical correlations have been established and commonly used to estimate the undrained shear strength of normally consolidated clays in geotechnical practice. However, there are still many contradictory cases regarding the validity of these correlations, so their applicability and reliability are questionable. In this study, an extensive geotechnical database for normally consolidated clays has been compiled. Next, a Bayesian nonparametric method is exploited to identify the most critical soil index properties in inferring the undrained shear strength and a new predictive model is proposed. Finally, the performance of the proposed predictive model is assessed and compared with two well-known correlations using an independent testing database. It confirms that the proposed model not only possesses high predictability, but also provides superior performance over other existing empirical correlations. 相似文献
12.
In this study, an effective means of dewatering the dredged material obtained from the sea-bottom in Istanbul is investigated through the use of additives and geotextile tubes (also known as geotubes, geotextile containers, and geotextile bags). Rapid dewatering test and geotube dewatering test are laboratory approaches, where the types and amounts of anionic and cationic additives for dewatering efficiency of dredged sludge can quickly and economically be examined. In this study, a best dosage amount of 1.5 kg/tonne was used as flocculant solution preparation with distilled water. After this process, twelve homogeneous sludge-polymer admixtures were prepared by adding 0.1, 0.5, and 1.0% polymers (anionic and cationic) by weight of the dredged material in rapid dewatering tests and another twelve homogeneous sludge-polymer admixtures were prepared by adding 0.1, 0.25, and 0.50% polymers (anionic and cationic) by weight of the dredged material in geotube dewatering tests. The results indicated that Golden Horn dredged sludge could be successfully dewatered and retained by geotextile tubes. The use of chemical cationic polymers is recommended with Golden Horn dredged sludge rather than the anionic polymers. Results also showed that use of flocculants can significantly increase the retention capacity of geotubes. 相似文献
13.
Extensive oedometer tests and physical tests have been conducted on remoldod and reconstituted marine soils with different initial water contents and liquid limits. The oedometer test data can be well fitted with a straight line in the bilogarithmin In(1 e)∽lg p plot. The initial effective stress corresponding to the initial void ratio is determined by extrapolation of the bilogarithmic compression line. This new way of extrapolating oedometer test data to the initial void ratio overcomes the difficulty of measuring the residual effective stress of soils in the remolded state. The initial stable compression line of ocean floor deposits under different deposition environments corresponds to the compression line at the sensitivity equal to one. This initial stable compression line obtained in this study is consistent with the available compression line at the sensitivity equal to one which is proposed based on the experimental data of remolded undrained strength and the theoretical concept of Cam-clay critical state line. 相似文献
14.
In this study, a stochastic method was applied to investigate if there exists a statistical correlation between values of undrained shear strength at various vertical distances along Golden Horn. Therefore, the undrained shear strength values measured by field vane shear tests at different depths were used to determine the depth dependent variation of the mean value and standard deviation. Futhermore, autocorrelation functions were defined to describe the correlation between values of cu at different depths. The study showed that the applied method might provide a statistical range to estimate the undrained shear strength value at depths where no measurements are undertaken. 相似文献
15.
Chaitanya Vardhan 《Marine Georesources & Geotechnology》2013,31(4):305-316
Residual undrained shear strength, s u_res , is an important parameter for analyzing the response of structures buried within potentially unstable soil mass. A framework for estimating s u_res of fine grained sediments from gravity corer penetration has been developed considering viscous drag during free fall of the corer through seawater and cohesive energy loss during sediment penetration. The procedure was used to estimate s u_res using data from a submarine geotechnical investigation in western Canada. Comparison of the results with alternative estimates of s u_res from miniature torvane tests on the gravity core samples and CPTs performed nearby reveals a reasonable agreement. 相似文献
16.
The use of the piezocone penetration test (CPTU) in a geotechnical site investigation offers direct field measurement on stratigraphy and soil behavior. Compared with some traditional investigation methods, such as drilling, sampling and field inspecting method or laboratory test procedures, CPTU can greatly accelerate the field work and hereby reduce corresponding operation cost. The undrained shear strength is a key parameter in estimation of the stability of natural slopes and deformation of embankments in soft clays. This paper provides the measurements of in situ CPTU, field vane testing and laboratory undrained triaxial testing of Lianyungang marine clay in Jiangsu province of China. Based on the literature review of previous interpretation methods, this paper presents a comparison of field vane testing measurements to CPTU interpretation results. The undrained shear strength values from both the field vane tests and cone penetration resistances are lowest at the mid-depths of the marine clay layers, and the excess pore water pressures are highest at the mid-depths of the marine clay layers, indicating that the marine clay layer is underconsolidated. 相似文献
17.
Residual undrained shear strength, su_res, is an important parameter for analyzing the response of structures buried within potentially unstable soil mass. A framework for estimating su_res of fine grained sediments from gravity corer penetration has been developed considering viscous drag during free fall of the corer through seawater and cohesive energy loss during sediment penetration. The procedure was used to estimate su_res using data from a submarine geotechnical investigation in western Canada. Comparison of the results with alternative estimates of su_res from miniature torvane tests on the gravity core samples and CPTs performed nearby reveals a reasonable agreement. 相似文献
18.
ABSTRACT This article presents a testing study on the strain-rate effects on the stress--strain behavior of natural, undisturbed Hong Kong marine deposits (HKMD) from three Hong Kong locations, including a one-dimensional (1-D) compressibility in a confined condition, and undrained shear strengths in triaxial compression and extension modes. The influences of the strain rates on the one-dimensional compressibility are studied by means of constant rate of strain (CRS) tests and multistage loading oedometer (MSL) tests, and those on the undrained shear strengths are studied by K o-consolidated undrained compression and extension tests with step-changed axial strain rates (CK oUC and CK oUE tests), and with both step-changed axial strain rates and relaxation processes (CK oUCR and CK oUER tests). The strain-rate effects on the stress--strain behavior are generally examined by “apparent” preconsolidation pressures in the 1-D compressions and undrained shear strengths in the triaxial compression and extension stress states. The stress--strain behavior of the natural, undisturbed HKMD exhibits considerable viscous characteristics. In the CRS and MSL tests at a given strain, the higher the strain rate, the higher the effective stress, the higher the porewater pressure. In the undrained shearing tests, the higher the strain rate, the higher the undrained shear strength, but the lower the porewater pressure. For the CK oUC and CK oUE tests on the Tsing Yi site samples, the undrained shear strength increases by 8.5% and 12.1% for one order increment of axial strain rate of 0.2%/hr (i.e., ρ0.2) for the compression and extension modes respectively. For the CK oUCR and CK o tests on the Tung Chung site samples of different compositions, average ρ0.2 is increased by 6.2% for the compression and 9.5% for the extension, but by 18.8% for the extension on a higher plastic sample. The present study shows that the strain-rate effects on the stress--strain behavior of the undisturbed HKMD are larger for specimens in extension than those in compression. 相似文献
19.
This article presents a testing study on the strain-rate effects on the stress--strain behavior of natural, undisturbed Hong Kong marine deposits (HKMD) from three Hong Kong locations, including a one-dimensional (1-D) compressibility in a confined condition, and undrained shear strengths in triaxial compression and extension modes. The influences of the strain rates on the one-dimensional compressibility are studied by means of constant rate of strain (CRS) tests and multistage loading oedometer (MSL) tests, and those on the undrained shear strengths are studied by Ko-consolidated undrained compression and extension tests with step-changed axial strain rates (CKoUC and CKoUE tests), and with both step-changed axial strain rates and relaxation processes (CKoUCR and CKoUER tests). The strain-rate effects on the stress--strain behavior are generally examined by “apparent” preconsolidation pressures in the 1-D compressions and undrained shear strengths in the triaxial compression and extension stress states. The stress--strain behavior of the natural, undisturbed HKMD exhibits considerable viscous characteristics. In the CRS and MSL tests at a given strain, the higher the strain rate, the higher the effective stress, the higher the porewater pressure. In the undrained shearing tests, the higher the strain rate, the higher the undrained shear strength, but the lower the porewater pressure. For the CKoUC and CKoUE tests on the Tsing Yi site samples, the undrained shear strength increases by 8.5% and 12.1% for one order increment of axial strain rate of 0.2%/hr (i.e., ρ0.2) for the compression and extension modes respectively. For the CKoUCR and CKo tests on the Tung Chung site samples of different compositions, average ρ0.2 is increased by 6.2% for the compression and 9.5% for the extension, but by 18.8% for the extension on a higher plastic sample. The present study shows that the strain-rate effects on the stress--strain behavior of the undisturbed HKMD are larger for specimens in extension than those in compression. 相似文献
20.
This article presents results from a series of Ko-consolidated compression and extension triaxial tests on specimens from undisturbed samples of Hong Kong Marine Deposits (HKMD). To investigate the strain-rate effects, a total of seven Ko-consolidated triaxial tests were conducted including four compression tests and three extension tests. After Ko-consolidation, the triaxial test specimens were sheared at step-changed axial strain rates under three different confining pressures of 50 kPa, 150 kPa, and 400 kPa, respectively. The step-changed strain rates were applied in the following order: +2%/h, +0.2%/h, +20%/h, -2%/h (unloading) and +2%/h (reloading) for the four compression tests and -2%/h, -0.2%/h, -20%/h, +2%/h (unloading) and -2%/h (reloading) for the three extension tests. The results are reported and analyzed in the paper. The results show that the strain rate effects, the stress-strain characteristics, and the effective stress paths of the specimens for tests in a compression state are different from those for tests in an extension stage. One order of magnitude increase in axial strain rate causes an average 8.6% increase in undrained shear strength for compression tests and a 12.1% increase for extension tests. It is also found that the failure mode of the specimens in compression is different from that in extension. The stress-strain behavior of specimens shows strain-softening and a clear shear band in compression tests, but strain-hardening without any clear shear band in extension tests for the same absolute value of axial strain. 相似文献