Initiation Analysis of an Irrigation-Induced Loess Landslide

2012 ◽  
Vol 170-173 ◽  
pp. 574-580 ◽  
Author(s):  
Hong Jie Li ◽  
Yan Li Jin
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
High Water ◽  
Underground Water ◽  
Shanxi Province ◽  
Triaxial Tests ◽  
High Water Content ◽  
Compression Tests ◽  
Loess Landslide ◽  
Water Level Rise

Underground water level rise because of irrigation has induced a lot of loess landslides in South Jingyang Plateau located in Shanxi Province, PR China. This paper presents a detailed initiation analysis of the landslides through field investigations, a series of GDS triaxial tests composed of isotropically and anisotropically consolidated undrained (ICU/ACU) compression tests and constant-shear-drained (CQD) triaxial tests for undisturbed saturated loess and numerical modeling. The tests show that the contractive failure will cause excess pore water pressure that cannot be dissipated instantly, and will result in the decrease of the shearing resistance. Shear deformation during failure moves the soil toward the critical state rapidly and make the loess completely in liquefactive condition. Therefore, the slope is prone to rapid and long run-out flow slide after failure under the action of gravity because of its high water content.

scholarly journals Field Study on the Waterstop of the Rodin Jet Pile Method in a Water-Rich Sandy Gravel Stratum

2019 ◽  
Vol 9 (8) ◽  
pp. 1709
Author(s):  
Chengli Guan ◽  
Yuyou Yang
Keyword(s):  
High Pressure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Field Tests ◽  
High Water ◽  
High Water Content ◽  
Sandy Gravel ◽  
Ultra High Pressure ◽  
Jet Grouting ◽  
Silty Soils

Due to the increasing depths of underground urban construction, the surrounding environment and hydrogeological conditions are becoming increasingly complex, and conventional high-pressure rotary jet grouting has become unable to meet construction needs. At present, Rodin jet pile (RJP) ultra-high-pressure rotary jet grouting has been widely used as a grouting reinforcement method for deep and large foundations in silty soils, fine sands and clay strata; however, there have been no successful applications in a sandy gravel stratum with high water content (namely, water-rich sandy gravel stratum). Therefore, this paper uses the ventilating shaft in a section of the Beijing Metro as the construction background to carry out field tests on the RJP ultra-high-pressure rotary jet grouting method and waterstop in a water-rich sandy gravel stratum. Through a series of experiments monitoring the formation deformation and pore water pressure and exposing the pile diameter, pile occlusion, pile strength, and permeability of the test pile construction process, it is believed that, for the RJP ultra-high-pressure construction method in a water-rich sandy gravel stratum, reliable jet solidification can occur, the joint between jets can be achieved, the solid strength can reach 10 MPa or higher, and the permeability coefficient can reach 10−8 cm/s. Therefore, RJP ultra-high-pressure rotary jet grouting can be applied as a waterstop method in water-rich sandy gravel stratum.

Experimental Research of Soft Soil Ground Treatment in Yangpu Port by Static-Dynamic Drainage Consolidation

2013 ◽  
Vol 353-356 ◽  
pp. 203-207
Author(s):  
Yong Kang Yang ◽  
Wu Yang ◽  
Chun Yan Feng
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Drainage System ◽  
Physical And Mechanical Properties ◽  
High Water ◽  
Surface Settlement ◽  
High Water Content ◽  
Engineering Practice ◽  
Ground Treatment

Yangpu Port has inhomogeneous soft soil with the properties of high water content, high void ratio, high compressibility and low shear strength. Based on soft soil ground treatment engineering practice, the geological characteristics are summarized, the ground treatment methods are comparatively analyzed, static-dynamic drainage consolidation method is chosen to treat the soft soil ground, the reinforcing mechanism of vertical and horizontal drainage system are discussed, the design of drainage system, preloading and dynamic consolidation are researched and the surface settlement monitoring, pore water pressure monitoring, side piling displacement monitoring, laboratory soil test and plate loading tests are carried out. The results show that average surface settlement is 1170.8 mm, the physical and mechanical properties of soft soil are improved and the characteristic value of foundation bearing capacity is greater than 120kPa.

scholarly journals Stability and Consolidation of Sediment Tailings Incorporating Unsaturated Soil Mechanics

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 423
Author(s):  
Alfrendo Satyanaga ◽  
Martin Wijaya ◽  
Qian Zhai ◽  
Sung-Woo Moon ◽  
Jaan Pu ◽  
...  
Keyword(s):  
Unsaturated Soil ◽  
Pore Water Pressure ◽  
Soil Mechanics ◽  
Water Pressure ◽  
High Water ◽  
Degree Of Saturation ◽  
High Water Content ◽  
Consolidation Process ◽  
Time Required ◽  
Unsaturated Zones

Tailing dams are commonly used to safely store tailings without damaging the environment. Sand tailings (also called Sediment tailings) usually have a high water content and hence undergo consolidation during their placement. As the sediment tailings are usually placed above the ground water level, the degree of saturation and permeability of the sediment tailing is associated with the unsaturated condition due to the presence of negative pore-water pressure or suction. Current practices normally focus on the analyses saturated conditions. However, this consolidation process requires the flow of water between saturated and unsaturated zones to be considered. The objective of this study is to investigate the stability and consolidation of sediment tailings for the construction of road pillars considering the water flow between saturated and unsaturated zones. The scope of this study includes the unsaturated laboratory testing of sediments and numerical analyses of the road pillar. The results show that the analyses based on saturated conditions overestimate the time required to achieve a 90% degree of consolidation. The incorporation of the unsaturated soil properties is able to optimize the design of slopes for road pillars into steeper slope angles.

Static response of fly ash columnar improved ground

2001 ◽  
Vol 38 (2) ◽  
pp. 276-286 ◽  
Author(s):  
A Porbaha ◽  
T BS Pradhan ◽  
T Kishida
Keyword(s):  
Fly Ash ◽  
Stress Concentration ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Area Ratio ◽  
Stress Redistribution ◽  
Soft Ground ◽  
Compression Tests ◽  
Composite Ground

This study presents the results of a series of monotonic undrained triaxial compression tests on clay specimens improved by columnar reinforcement. The process of loading and stress redistribution of a fly ash – clay specimen (FCS), in comparison with a sand–clay specimen (SCS), is examined in terms of stress–strain characteristics, generation of excess pore-water pressure, effective and total earth pressures, development of stress concentration, and the normalized undrained shear strength of the improved soil. It was found, predictably, that the deviator stress of the composite specimens was influenced by the consolidation stress, replacement area ratio, and properties of the column material. The stress concentration at the top of the composite ground which depends on the loading stage reaches a peak after the consolidation state and is reduced due to stress redistribution between the column and the soft ground. In terms of improvement effects, the mean shear strengths of FCS and SCS relative to the clay specimen are three and seven times greater, respectively, for a replacement area ratio of 49%.Key words: composite ground, fly ash, soil improvement, soft ground, triaxial test.

scholarly journals Soil liquefaction as an identification test

2019 ◽  
Vol 92 ◽  
pp. 08008
Author(s):  
Bozana Bacic ◽  
Ivo Herle
Keyword(s):  
Pore Water ◽  
Laboratory Testing ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Initial Density ◽  
Soil Liquefaction ◽  
Triaxial Tests ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Identification Test

Time-consuming and complicated investigations of soil liquefaction in cyclic triaxial tests are the most common way of laboratory analysis of this phenomenon. Moreover, the necessary equipment for the performance of cyclic triaxial tests is very expensive. Much simpler method for laboratory testing of the soil liquefaction has been developed at the Institute of Geotechnical Engineering at the TU Dresden. This method takes into account the pore water pressure build-up during cyclic shearing within a short time period. During the test, the soil sample is subjected to horizontal cyclic loading and the generated pore water pressure is measured. In the first series of these experiments, a dependence of the pore water pressure buildup on the initial density of soil could be observed, as expected. When comparing different soils, it is shown that the tendency to liquefaction depends also on the granulometric properties (e.g. grain size distribution) of the soil. The aim of the further development is to establish a simple identification test for laboratory testing of the soil liquefaction.

scholarly journals Implications of the principle of effective stress

2020 ◽  
Author(s):  
Gerd Gudehus
Keyword(s):  
Critical Phenomena ◽  
Pore Water ◽  
Effective Stress ◽  
Critical Points ◽  
Pore Water Pressure ◽  
Numerical Models ◽  
Water Pressure ◽  
Shear Bands ◽  
Triaxial Tests ◽  
Water Saturated

AbstractWhile Terzaghi justified his principle of effective stress for water-saturated soil empirically, it can be derived by means of the neutrality of the mineral with respect to changes of the pore water pressure $$p_w$$ p w . This principle works also with dilating shear bands arising beyond critical points of saturated grain fabrics, and with patterns of shear bands as relics of critical phenomena. The shear strength of over-consolidated clay is explained without effective cohesion, which results also from swelling up to decay, while rapid shearing of water-saturated clay can lead to a cavitation of pore water. The $$p_w$$ p w -neutrality is also confirmed by triaxial tests with sandstone samples, while Biot’s relation with a reduction factor for $$p_w$$ p w is contestable. An effective stress tensor is heuristically legitimate also for soil and rock with relics of critical phenomena, particularly for critical points with a Mohr–Coulomb condition. Therein, the $$p_w$$ p w -neutrality of the solid mineral determines the interaction of solid fabric and pore water, but numerical models are questionable due to fractal features.

scholarly journals Influence of initial fines content on fabric of soils subjected to internal erosion

2016 ◽  
Vol 53 (2) ◽  
pp. 299-313 ◽  
Author(s):  
Mao Ouyang ◽  
Akihiro Takahashi
Keyword(s):  
Pore Water Pressure ◽  
Axial Strain ◽  
Water Pressure ◽  
Internal Erosion ◽  
Experimental Investigations ◽  
Compression Tests ◽  
Fines Content ◽  
Instability Zone ◽  
Before And After ◽  
Undrained Behavior

Seepage-induced internal erosion often happens in earth structures. This paper presents experimental investigations on the influence of initial fines content on fabric of soils subjected to internal erosion. The tested materials were the binary mixtures of silica No. 3 and silica No. 8, which correspond to the coarse and fine fractions, respectively. One group of specimens was prepared with initial fines contents of 0, 15%, 25%, and 35% by weight. The undrained monotonic compression tests were performed on this group to examine the influence of fines content on the undrained behavior. The other group was prepared with initial fines contents of 15%, 25%, and 35% by weight, on which the seepage tests and subsequent undrained compression tests were carried out to demonstrate the mechanical influence of the internal erosion. The undrained behavior of the first group of specimens reveals that the presence of fines would decrease the peak and residual strengths. A comparison between the undrained behavior of soils with erosion and that of soils without erosion shows that the soils become less contractive after the internal erosion. When the axial strain is less than 0.4%, the undrained secant stiffness of soils with erosion is larger than that without erosion at the same axial strain. Meanwhile, the undrained peak strength and residual strength are larger for soils with erosion than that for soils without erosion. The less amount of excess pore-water pressure is generated during the undrained compression for the eroded soils comparing to those of the uneroded soils. Furthermore, the eroded soils show a wider instability zone than that of the uneroded soils, which suggests that the instability zone be enlarged by the internal erosion. Besides, one-dimensional upward seepage tests were performed to investigate the change of fabric of the mixed sand with 15%, 25%, and 35% fines contents due to internal erosion. The recorded microscopic images of soils before and after erosion reveal that the fabric is altered by the internal erosion.

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