scholarly journals Mechanical State of Gravel Soil in Mobilization of Rainfall-Induced Landslide in Wenchuan seismic area, Sichuan province, China

2018 ◽  
Author(s):  
Liping Liao ◽  
Yunchuan Yang ◽  
Zhiquan Yang ◽  
Yingyan Zhu ◽  
Jin Hu ◽  
...  
Keyword(s):  
Fine Particle ◽  
Void Ratio ◽  
State Parameter ◽  
Particle Migration ◽  
Triaxial Tests ◽  
Dry Density ◽  
Mechanical State ◽  
Consolidation Process ◽  
Gravel Soil ◽  
Seismic Area

Abstract. Although gravel soils generated by seismic shaking in Wenchuan earthquake area have subjected to natural consolidation process for nearly ten years, geological hazards, such as slope failures with ensuing landslides, frequently are haunting the area. In this paper, artificial flume model tests and triaxial tests were used to make close observation on the mechanical state of gravel soil in Wenchuan seismic area. The results showed that: (1) The timing and patterns of landslide initiations were closely related to their initial dry densities, and the initiation processes were accompanied with a variation of dry density and void ratio; (2) Fine particle migration in soil and coarse-fine particle content rearrangement contributed to the internal micro structure reorganization, which was supposed to be the main reason for variation of dry density and void ratio; (3) Gravel soils with unchanged grain compositions, if under the same hydrostatic compression, they approached to an identical critical void ratio to fail; (4) The mechanical state of certain sort of gravel soil can be identified by its relative position between state parameter (e, p') and ec-p' planar critical state line; (5) Gravel soil slope failed and then evolved into landslide under lasting rainfall leaching, while in gravel slope there co-existed soil dilatation and contraction, but the dilatation was dominant. Above research findings not only could be used to interpret landslide initiation but also would provide an insight for landslide warning forecast of gravel slope in seismic area.

scholarly journals Mechanical state of gravel soil in mobilization of rainfall-induced landslides in the Wenchuan seismic area, Sichuan province, China

2018 ◽  
Vol 6 (3) ◽  
pp. 637-649
Author(s):  
Liping Liao ◽  
Yunchuan Yang ◽  
Zhiquan Yang ◽  
Yingyan Zhu ◽  
Jin Hu ◽  
...  
Keyword(s):  
Critical State ◽  
Void Ratio ◽  
Fine Particles ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
State Parameter ◽  
Confining Pressure ◽  
Dry Density ◽  
Mechanical State ◽  
Gravel Soil

Abstract. Gravel soils generated by the Wenchuan earthquake have undergone natural consolidation for the past decade. However, geological hazards, such as slope failures with ensuing landslides, have continued to pose great threats to the region. In this paper, artificial model tests were used to observe the changes of soil moisture content and pore water pressure, as well as macroscopic and microscopic phenomena of gravel soil. In addition, a mathematical formula of the critical state was derived from the triaxial test data. Finally, the mechanical states of gravel soil were determined. The results had five aspects. (1) The time and mode of the occurrence of landslides were closely related to the initial dry density. The process of initiation was accompanied by changes in density and void ratio. (2) The migration of fine particles and the rearrangement of coarse–fine particles contributed to the reorganization of the microscopic structure, which might be the main reason for the variation of dry density and void ratio. (3) If the confining pressure were the same, the void ratios of soils with constant particle composition would approach approximately critical values. (4) Mechanical state of gravel soil can be determined by the relative position between state parameter (e, p′) and ec–p′ planar critical state line, where e is the void ratio, ec is the critical void ratio and p′ is the mean effective stress. (5) In the process of landslide initiation, dilatation and contraction were two types of gravel soil state, but dilatation was dominant. This paper provided insight into interpreting landslide initiation from the perspective of critical state soil mechanics.

Drained instability of sand in plane strain

2010 ◽  
Vol 47 (4) ◽  
pp. 400-412 ◽  
Author(s):  
Dariusz Wanatowski ◽  
Jian Chu ◽  
Wai Lay Loke
Keyword(s):  
Experimental Data ◽  
Plane Strain ◽  
Case Studies ◽  
Static Loading ◽  
State Parameter ◽  
Dam Failure ◽  
Triaxial Tests ◽  
Granular Soil ◽  
Laboratory Studies ◽  
Dense Sand

Flowslide or failure of loose granular soil slopes is often explained using liquefaction or instability data obtained from undrained triaxial tests. However, under static loading conditions, the assumption of an undrained condition is not realistic for sand, particularly clean sand. Case studies have indicated that instability of granular soil can occur under essentially drained conditions (e.g., the Wachusett Dam failure in 1907). Laboratory studies on Changi sand by Chu et al. in 2003 have shown that sand can become unstable under completely drained conditions. However, these studies were carried out under axisymmetric conditions and thus, cannot be applied directly to the analysis of slope failures. In this paper, experimental data obtained from plane-strain tests are presented to study the instability behaviour of loose and dense sand under plane-strain conditions. Based on these test data, the conditions for the occurrence of drained instability in plane strain are established. Using the modified state parameter, the conditions for instability under both axisymmetric and plane-strain conditions can be unified. A framework for interpreting the instability conditions of sandy slopes developed under axisymmetric conditions also extends into plane-strain conditions.

Effects of fines on liquefaction behaviour in well-graded materials

2017 ◽  
Vol 54 (10) ◽  
pp. 1460-1471 ◽  
Author(s):  
Katherine A. Kwa ◽  
David W. Airey
Keyword(s):  
Critical State ◽  
Soil Mechanics ◽  
State Parameter ◽  
Triaxial Tests ◽  
Particle Sizes ◽  
Graded Materials ◽  
Fines Content ◽  
Cyclic Resistance ◽  
Wide Range ◽  
Soil Behaviour

This study uses a critical state soil mechanics perspective to understand the mechanics behind the liquefaction of metallic ores during transport by ship. These metallic ores are transported at relatively low densities and have variable gradings containing a wide range of particle sizes and fines contents. The effect of the fines content on the location of the critical state line (CSL) and the cyclic liquefaction behaviour of well-graded materials was investigated by performing saturated, standard drained and undrained monotonic and compression-only cyclic triaxial tests. Samples were prepared at four different gradings containing particle sizes from 9.5 mm to 2 μm with fines (<75 μm) contents of 18%, 28%, 40%, and 60%. In the e versus log[Formula: see text] plane, where e is void ratio and [Formula: see text] is mean effective stress, the CSLs shifted upwards approximately parallel to one another as the fines content was increased. Transitional soil behaviour was observed in samples containing 28%, 40%, and 60% fines. A sample’s cyclic resistance to liquefaction depended on a combination of its density and state parameter, which were both related to the fines content. Samples with the same densities were more resistant to cyclic failure if they contained higher fines contents. The state parameter provided a useful prediction for general behavioural trends of all fines contents studied.

A Change of Undrain Shear Strength of Soft Ground during Consolidation Process

2014 ◽  
Vol 513-517 ◽  
pp. 269-272
Author(s):  
Yeong Mog Park ◽  
Ik Joo Um ◽  
Norihiko Miura ◽  
Seung Cheol Baek
Keyword(s):  
Shear Strength ◽  
Soft Clay ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Test Results ◽  
Exponential Equation ◽  
Consolidation Process ◽  
Degree Of Consolidation ◽  
Clay Ground ◽  
Strength Increment

The purpose of this study is to investigate the undrain shear strength increment during consolidation process of soft clayey soils. Thirty kinds of laboratory triaxial tests have been performed using undisturbed and remolded Ariake clay samples with different degree of consolidation and 5 kinds of confining pressure. Test results show that well known linear equation proposed by Yamanouchi et al.(1982) is overestimated the strength of undisturbed soft clay ground in the process of consolidation. A new simple and reasonable exponential equation proposed in this paper.

scholarly journals An Experimental Study on the Shear Behaviors of Polymer-Sand Composite Materials after Immersion

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 924 ◽  
Author(s):  
Jin Liu ◽  
Yuxia Bai ◽  
Ding Li ◽  
Qiongya Wang ◽  
Wei Qian ◽  
...  
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Void Ratio ◽  
Dry Density ◽  
Chemical Additives ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Sand Particles ◽  
Shear Behaviors ◽  
Sand Material

Sand mixed with geotextile/fiber/cement/lime or non-traditional chemical additives to form composite materials is recognized as an effective method for improving the sand properties. In this work, the variation in properties of composite materials after immersion is reported which has rarely appeared in the literature. The focus of this study is to evaluate the shear behaviors of polymer-sand composite material after immersion with direct shear tests. Several factors which may influence the shear behaviors after immersion are analyzed. The results demonstrate that this composite material still has good shear behaviors after immersion when compared to the purely sand material. The shear behaviors are improved with an increment in the curing time, polymer content and sand dry density while there is a decrease in the shear behaviors with increasing immersion time. The interaction between sand particles and the polymer are analyzed with Scanning Electron Microscope (SEM). The polymer membranes are formed by polymer enwrapping and connected sand particles to build an elastic and viscous structure in the sand that increases the interlocking forces between sand particles and decreases the void ratio of this material. The membranes are softened in water resulting in a decrease in the shear strength. Moreover, other factors affect the shear behaviors by improving the completeness and stability of this structure.

A geological approach toward developing a mudrock-durability classification system

1994 ◽  
Vol 31 (1) ◽  
pp. 17-27 ◽  
Author(s):  
Jeffrey C. Dick ◽  
Abdul Shakoor ◽  
Neil Wells
Keyword(s):  
North America ◽  
Key Words ◽  
Classification System ◽  
Void Ratio ◽  
Clay Content ◽  
Dry Density ◽  
Slake Durability Index ◽  
Durability Index ◽  
Degree Of Consolidation ◽  
Clay Mineral Composition

Relationships between durability and lithologic characteristics of 61 mudrock samples from North America were investigated with the objective of developing a mudrock-durability classification based on lithologic characteristics. Second-cycle slake-durability index (Id2) was used as a measure of durability, whereas clay content, clay-mineral composition, texture, microfracture frequency, absorption, adsorption, dry density, void ratio, and Atterberg limits were used to characterize mudrock lithology. Based upon the amount of clay-size material, the presence or absence of laminations, and the degree of induration, the mudrocks were subdivided into claystones, mudstones, siltstones, shales, and argillites. The relationships between durability and lithologic characteristics were investigated separately for each class of mudrocks. The results show that different lithologic characteristics best correlate with the durability of each class of mudrocks. The durability of claystones correlates best with the amount of expandable clay minerals and that of mudstones with the frequency of microfractures. The degree of consolidation, as expressed by absorption, influences the durability of both siltstones and shales. The durability of argillites is related to their crystalline texture. Lithologic characteristics can be quantitatively related to a durability classification proposed herein that recognizes three classes of durability: low (Id2 < 50%), medium (Id2 = 50%–85%), and high (Id2 > 85%). Key words : mudrock, durability, lithologic characteristics, classification.

Mode of shear effects on yield and liquefied strength ratios

2008 ◽  
Vol 45 (4) ◽  
pp. 574-587 ◽  
Author(s):  
Scott M. Olson ◽  
Benjamin B. Mattson
Keyword(s):  
Simple Shear ◽  
Void Ratio ◽  
Triaxial Compression ◽  
State Parameter ◽  
Sloping Ground ◽  
Direct Simple Shear ◽  
Flow Failure ◽  
Triaxial Extension Test ◽  
Triaxial Extension ◽  
Rotational Shear

A database of 386 laboratory triaxial compression, direct simple shear, rotational shear, and triaxial extension test results was collected to examine yield and liquefied strength ratio concepts used in liquefaction analysis of sloping ground. These data envelope the yield and liquefied strength ratios obtained from back-analyses of liquefaction flow failure case histories. Generally, triaxial compression exhibits the highest yield and liquefied strength ratios, triaxial extension yields the lowest ratios, and direct simple shear – rotational shear shows intermediate responses. However, mode of shear appears to have a considerably smaller effect on laboratory-measured liquefied strength ratios for specimens with a positive state parameter (i.e., difference in consolidation void ratio and steady state void ratio at the same effective stress).

Engineering Application of Detections on Backfill Compactness

2012 ◽  
Vol 204-208 ◽  
pp. 101-106
Author(s):  
Shi Min Zhang ◽  
Lei Zhang
Keyword(s):  
Heat Exchange ◽  
Detection Method ◽  
Engineering Application ◽  
Dry Density ◽  
Maximum Dry Density ◽  
Gravel Soil ◽  
Heat Exchange Equipment ◽  
Forward Problems ◽  
Important Basis

This thesis introduces the contents of backfill compactness and the detection method. And it also introduces the effects of backfill compactness in engineering: it is an important basis to judge the reliability and stability of backfill foundation. In addition, it takes the maximum dry density detection of on-site backfill and the compacted backfill compactness detection of foundation at Linan contrustion site of Hangzhou Hangyang Heat Exchange Equipment Co., Ltd. for example to specify the engineering application of detections of backfill compactness. At last it puts forward problems existing in the engineering detection on compacted backfill compactness: the variance of the actual maximum dry density and maximum dry density achieved by indoor compaction experiment. And it also provides a corresponding solution called the correction for maximum dry density in sieved gravel soil.

Geotechnical characteristics of recycled crushed brick blends for pavement sub-base applications

2012 ◽  
Vol 49 (7) ◽  
pp. 796-811 ◽  
Author(s):  
A. Arulrajah ◽  
J. Piratheepan ◽  
M.W. Bo ◽  
N. Sivakugan
Keyword(s):  
Recycled Concrete ◽  
Engineering Properties ◽  
Triaxial Tests ◽  
Crushed Rock ◽  
Dry Density ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Crushed Brick ◽  
Repeated Load ◽  
Repeated Load Triaxial

This paper presents the findings of a laboratory investigation on the characterization of recycled crushed brick when blended with recycled concrete aggregate and crushed rock for pavement sub-base applications. The engineering properties of the crushed brick blends were compared with typical state road authority specifications in Australia for pavement sub-base systems to ascertain the potential use of crushed brick blends in these applications. The experimental programme included particle-size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio (CBR), Los Angeles abrasion, pH, organic content, and repeated load triaxial tests. Laboratory tests were undertaken on mixtures of 10%, 15%, 20%, 25%, 30%, 40%, and 50% crushed brick blended with recycled concrete aggregate or crushed rock. The research indicates that up to 25% crushed brick could be safely added to recycled concrete aggregate and crushed rock blends in pavement sub-base applications. The repeated load triaxial test results on the blends indicate that the effects of crushed brick content on the mechanical properties in terms of permanent deformation and resilient modulus of both the recycled concrete aggregate and crushed rock blends were marginal compared to the effects on dry density and moisture content.

scholarly journals MECHANICAL PROPERTIES OF BOTTOM ASH – DREDGED MATERIAL MIXTURES IN LABORATORY TESTS

2013 ◽  
Vol 35 (3) ◽  
pp. 3-11 ◽  
Author(s):  
Lech Bałachowski ◽  
Zbigniew Sikora
Keyword(s):  
Mechanical Properties ◽  
Void Ratio ◽  
Bottom Ash ◽  
Physical And Mechanical Properties ◽  
Friction Angle ◽  
Ash Content ◽  
Dry Density ◽  
Dredged Material ◽  
Maximum Dry Density ◽  
Proctor Test

Abstract Bottom ash from EC Gdańsk and dredged material taken from the mouth of The Vistula were mixed to form an engineering material used for dike construction. Mixtures with different bottom ash content were tested in laboratory to determine its basic physical and mechanical properties. The optimum bottom ash-dredged material mixture, built in the corps of the test dike, contains 70% of ash. The optimum bottom ash content in the mixture was chosen taking into account high internal friction angle, good compaction and reduced filtration coefficient. The maximum dry density of the mixtures was measured in Proctor test for the mixtures formed in laboratory and on samples taken from the test dike. Minimum and maximum void ratio were also determined.

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