scholarly journals Microscopic Mechanism Affecting Shear Strength in Lignin-Treated Loess Samples

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Wei Liu ◽  
Juan Wang ◽  
Gaochao Lin ◽  
Li Wen ◽  
Qian Wang
Keyword(s):  
Shear Strength ◽  
Lignin Content ◽  
Axial Stress ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Microscopic Mechanism ◽  
Valley Fill ◽  
Fill Material ◽  
Excess Pore

In China, engineers have worked to create additional usable land for building construction by flattening the ridges of hills and filling in the adjacent valleys. China’s Loess Plateau comprises a type of soil (loess) with a large pore structure that can collapse and become unstable when exposed to groundwater. Conventional valley fill materials include remolded loess or remolded loess treated with cement, lime, gypsum, or other stabilizing additives. These stabilizers are often detrimental to the surrounding environment. Moreover, loess treated with conventional stabilizers exhibits excessive brittleness, which is not suitable for building foundations. Adequate stability of the building foundations in the filled valleys is required to ensure public safety. In this study, we tested 50 remolded loess samples treated with a lignin polymer compound to determine its potential as a valley fill material. Triaxial tests, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to study the mechanical characteristics of each sample, determine the effects of the lignin treatment on the loess, and identify the microscopic mechanism affecting shear stress in the lignin-treated loess. The corresponding development of excess pore pressure and volumetric responses under monotonic triaxial testing were also considered. Based on this study’s results, the optimum lignin content in the treated loess samples was 4%; lignin contents exceeding 4% decreased axial stress and increased dilation after saturation. The shear strength and strain-hardening phenomenon of the lignin-treated loess samples increased as the lignin content increased, while the excess pore water pressure decreased. Microscopically, the addition of lignin increased cohesion in the loess samples, while slightly contributing to the internal friction angle. The use of lignin as a stabilizing additive for valley fill material shows potential for controlling building foundation deformation by increasing soil strength and minimizing environmental impacts by maintaining the soil pH and limiting pollutant production.

scholarly journals Experimental Investigation on the Behavior of Gravelly Sand Reinforced with Geogrid under Cyclic Loading

2021 ◽  
Vol 11 (24) ◽  
pp. 12152
Author(s):  
Jia-Quan Wang ◽  
Zhen-Chao Chang ◽  
Jian-Feng Xue ◽  
Zhi-Nan Lin ◽  
Yi Tang
Keyword(s):  
Cyclic Loading ◽  
High Speed ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Sand Sample ◽  
Loading Frequency ◽  
Gravelly Soil ◽  
Embedding Effect ◽  
Excess Pore

In view of the dynamic response of geogrid-reinforced gravel under high-speed train load, this paper explores the dynamic characteristics of geogrid-reinforced gravel under semi-sine wave cyclic loading. A number of large scale cyclic triaxial tests were performed on saturated gravelly soil reinforced with geogrid to study the influence of the number of reinforcement layers and loading frequencies on the dynamic responses of reinforced gravelly sand subgrade for high speed rail track. The variation of cumulative axial and volumetric strains, excess pore pressure and resilient modulus with number of loading cycles, loading frequency, and reinforcement arrangement are analyzed. The test results reveal that the cumulative axial strain decreases as the number of reinforcement layers increases, but increases with loading frequency. The resilience modulus increases with the number of reinforcement layers, but decreases as the loading frequency increases. The addition of geogrid can reduce the excess pore water pressure of the sample, but it can slightly enhance the rubber mold embedding effect of the sand sample. As the loading frequency increases, the rubber mold embedding effect gradually weakens.

Using piezocone dissipation test to estimate the undrained shear strength in cohesive soil

2015 ◽  
Vol 52 (3) ◽  
pp. 318-325 ◽  
Author(s):  
F.M. Mantaras ◽  
E. Odebrecht ◽  
F. Schnaid
Keyword(s):  
Shear Strength ◽  
Pore Pressure ◽  
Error Detection ◽  
Water Pressure ◽  
Undrained Shear Strength ◽  
Excess Pore Pressure ◽  
Engineering Practice ◽  
Stress History ◽  
Undrained Shear ◽  
Excess Pore

This paper describes a method developed to link the measured piezocone dissipation excess pore-water pressure (Δu) to the soil undrained shear strength (su). In cohesive soils, both Δu and su are dependent on the same variables (compressibility, stress state, stress history), which allows them to be related by the theoretical cavity expansion – critical state framework. A mathematical derivation is presented to demonstrate that the ratio of normalized maximum excess pore pressure and the normalized undrained shear strength fluctuates around a mean value, being affected by soil strength and compressibility and independent of stress history. The predicted su values obtained from the proposed approach are calibrated against field vane shear strength in both normally consolidated (monotonic dissipation tests) and overconsolidated soils (dilatory dissipation tests). Reported results are consistent and encourage the use of the method in engineering practice. On a routine basis, su estimated from pore pressure can be compared with values predicted from penetration resistance, adding desired redundancy for purposes of error detection when interpreting cone penetration testing with pore pressure measurement (CPTU) data.

scholarly journals The Liquefaction Behavior of Poorly Graded Sands Reinforced with Fibers

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Eyyüb Karakan ◽  
Tuğba Eskişar ◽  
Selim Altun
Keyword(s):  
Pore Water ◽  
Fiber Length ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Fiber Content ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Strong Impact ◽  
Fiber Reinforced ◽  
Excess Pore

This study focuses on the performance of fibers, improving the resistance to liquefaction in loose sands, medium sands, and dense sands in Izmir, Turkey. A systematic testing schedule consisting of cyclic triaxial tests was held under stress-controlled and undrained conditions on saturated sand specimens with and without fiber reinforcements. The major parameters having effects on the dynamic behavior such as fiber content, fiber length, and relative density on the liquefaction behavior and the excess pore water pressure developments of specimens with and without fibers were investigated. If the fiber content or the fiber length was increased in the specimens, higher number of loading cycles was needed in order to experience the liquefaction of sands. The reinforcement effect in medium-dense specimens was found to be apparently distinctive compared to loose specimens. The curves of pore water pressures and shear strains were achieved for the fiber-reinforced sands. The boundaries of pore water pressure curves presented in the literature on the clean sands were utilized in comparison with the pore water pressure curves of fiber-reinforced sands of this study. As a conclusion, the results presented in this study are useful to develop insight into the behavior of clean and fiber-reinforced sands under seismic loading conditions. Based on the test results, it was found that the number of loading cycles had a strong impact on the excess pore pressure generation.

The Test Study to the Changes of Excess Pore Water Pressure during Precast Pile Construction

2012 ◽  
Vol 193-194 ◽  
pp. 1010-1013
Author(s):  
Shu Qing Zhao
Keyword(s):  
Pore Water ◽  
Clayey Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Soil Pressure ◽  
Excess Pore Water Pressure ◽  
Test Study ◽  
Excess Pore

The construct to precast pile in thick clayey soil can cause the accumulation of excess pore water pressure. The high excess pore pressure can make soil, buildings and pipes surrounded have large deflection, even make them injured. Combining with actual projects, this paper presents an in-situ model test on the changes of excess pore water pressure caused by precast pile construct. It is found that the radius of influence range for single pile driven is about 15m，the excess pore water pressure can reach or even exceed the above effective soil pressure, and there are two relatively stable stages.

EXPERIMENT STUDY ON DYNAMIC STRENGTH OF LOESS UNDER REPEATED LOAD

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5825-5830 ◽  
Author(s):  
ZHENGHUA XIAO ◽  
BO HAN ◽  
HONGJIAN LIAO ◽  
AKENJIANG TUOHUTI
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Axial Strain ◽  
Water Pressure ◽  
Dynamic Strength ◽  
Triaxial Tests ◽  
Dynamic Shear ◽  
Anisotropic Consolidation ◽  
Dynamic Shear Strength

A series of dynamic triaxial tests are performed on normal anisotropic consolidation and over anisotropic consolidation specimens of loess. Based on the test results, the variable regularity of dynamic shear stress, axial strain and pore water pressure of loess under dynamic loading are measured and analyzed. The influences of the dynamic shear strength and pore water pressure at different over consolidation ratio are analyzed. The relationship between dynamic shear strength and over consolidation ratio of loess is obtained. The evaluating standard of dynamic shear strength of loess is discussed. Meanwhile, how to determine the effective dynamic shear strength index of normal anisotropic consolidated loess is also discussed in this paper. Several obtained conclusions can be referenced for studying the dynamic shear strength of loess foundation.

scholarly journals Experimental Investigation on Shear Strength and Liquefaction Potential of Rubber-Sand Mixtures

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Zhou Enquan ◽  
Wang Qiong
Keyword(s):  
Shear Strength ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Construction Materials ◽  
Horizontal Displacement ◽  
Triaxial Tests ◽  
Hyperbolic Model ◽  
Liquefaction Potential ◽  
Direct Shear Tests ◽  
Rubber Particles

The application of scrap tires as construction materials in civil engineering is one of the most promising ways to recycle this pollutant. The objective of this study was to investigate the shear strength and liquefaction potential of saturated rubber-sand mixtures. Direct shear tests and cyclic triaxial tests were conducted on rubber-sand mixtures at various rubber contents. It was found that the addition of rubber particles to sand changed the shear stress-horizontal displacement development. The addition of rubber particles to sand improved the shear strength slightly and improved resistance to liquefaction significantly. Additionally, a hyperbolic model was proposed to describe the pore water pressure generation. This study demonstrates the effect of rubber particles on the physical properties of sand.

Excess Pore Pressures During Undrained Clay Creep

1973 ◽  
Vol 10 (1) ◽  
pp. 12-24 ◽  
Author(s):  
Thomas L. Holzer ◽  
Kaare Höeg ◽  
Kandiah Arulanandan
Keyword(s):  
Pore Pressure ◽  
San Francisco ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Time Behavior ◽  
Pore Pressures ◽  
Undrained Creep ◽  
Excess Pore

The objective of this presentation is to examine experimentally how the excess pore-water pressure is related to the mechanism for undrained creep of San Francisco Bay mud. The results are discussed in the context of creep mechanisms previously suggested in the literature and based on laboratory testing.It is found that shear strains occurring during undrained creep are directly related to a gradual but significant increase in excess pore pressure and, hence, reduction in effective stresses. The increase in magnitude of the pore pressure is, except immediately after the creep shear stress is applied, solely a function of the initial consolidation stress and consolidation period. The magnitude of the long-term build-up may be related to the amount of secondary compression which would occur during drained conditions. It increases with the organic content of the soil and decreases with the degree of remolding. The mechanism for the increase in pore-water pressure may be explained by drainage of water from micropores in the microstructure into the macrostructure.Unless one accounts for the increase in pore pressures during undrained creep, it is unlikely that one will be successful in formulating a generally valid mathematical model for stress–strain–strength–time behavior based on laboratory testing.

scholarly journals Pore Pressure Response to Groundwater Fluctuations in Saturated Double-Layered Soil

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Hongwei Ying ◽  
Lisha Zhang ◽  
Kanghe Xie ◽  
Dazhong Huang
Keyword(s):  
Pressure Distribution ◽  
Pore Pressure ◽  
Dimensionless Parameter ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Layered Soil ◽  
Excess Pore Pressure ◽  
Groundwater Fluctuation ◽  
Excess Pore Pressures ◽  
Excess Pore

Analytical solutions are developed for one-dimensional consolidation of double-layered saturated soil subjected to groundwater fluctuations. The solutions are derived by an explicit mathematical procedure using Duhamel’s theorem in conjunction with a Fourier series, when groundwater fluctuation is described by a general time-dependent function and assumed to be the pore water pressure variations at the upper boundary. Taking as an example the harmonic groundwater fluctuation, the relevant response of the excess pore water pressure is discussed in detail, and the main influencing factors of the excess pore pressure distribution are analyzed. A dimensionless parameterθhas been introduced because it significantly affects the phase and the amplitude of excess pore pressures. The influences of the coefficients of permeability and compressibility of soil on the excess pore pressure distribution are different and cannot be incorporated into the coefficient of consolidation in double-layered soil. The relative permeability ratio of two clayey soils also plays an important role on the curves of the distributions of the excess pore pressures. The effects of the thickness of the soil layer on the excess pore pressure distribution should be considered together with the dimensionless parameterθand the permeability and compressibility of the double-layered soil system.

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