In situ shear tests of soil blocks with roots

1998 ◽  
Vol 35 (4) ◽  
pp. 579-590 ◽  
Author(s):  
Tien H Wu ◽  
Alex Watson
Keyword(s):  
Shear Strength ◽  
Root System ◽  
Tensile Force ◽  
Failure Surface ◽  
Soil Reinforcement ◽  
Shear Tests ◽  
Maximum Displacement ◽  
Shearing Resistance ◽  
Simplified Procedures

In situ shear tests were performed on soil blocks that contained roots to study the contribution of roots to the shear strength in a case where the shear deformation is not constrained to a thin zone. The shearing resistance of the soil-root system, the tensile force in selected roots, and the deformation of the soil block were measured. The roots were exposed after the test and their positions were determined and used to estimate the initial positions. The root force and the shearing resistance of the soil-root system were estimated with known solutions and compared with measured root force and shearing resistance. None of the roots that passed through the shear zone failed in tension at the maximum displacement. As a consequence, the root resistance is much less than that found in a case where the failure surface is restricted to the boundary between a weak soil and a firm base and where roots are anchored in the firm base and fail in tension. Simplified procedures for estimating root forces are suggested for the case of a thick shear zone.Key words: in situ test, roots, shear strength, slope stability, soil reinforcement, soil–root interaction.

Controlled displacement-rate in situ shear tests with pore pressure measurements

1985 ◽  
Vol 22 (1) ◽  
pp. 136-142 ◽  
Author(s):  
F. S. Shuri ◽  
D. D. Driscoll ◽  
S. J. Garner
Keyword(s):  
Shear Strength ◽  
Pore Pressure ◽  
Shear Zone ◽  
Large Scale ◽  
Bedding Plane ◽  
Western Canada ◽  
Shear Tests ◽  
Plane Shear ◽  
Clay Seam

Two large-scale in situ shear tests were conducted at a damsite in western Canada. The rock at the site is a Cretaceous shale containing a thin clay seam tentatively identified as a bedding-plane shear zone. The material in this seam is significantly weaker than the intact rock and influences the design of certain features of the dam and structures. In order to provide shear strength data for design, two large blocks of shale were sheared along the clay seam. These tests differed from conventional in situ shear tests in two significant ways: the rate of shear displacement was strictly controlled, and pore pressures (both positive and negative) in the shear zone were carefully monitored throughout the test. This note presents the material properties of the shear zone, describes the test equipment and techniques, and discusses the results obtained. Key words: shear strength, in situ testing, pore pressure, shale.

scholarly journals Mechanical Behaviour of Reinforced Sand with Natural Curauá Fibers through Full Scale Direct Shear Tests

2019 ◽  
Vol 92 ◽  
pp. 12003
Author(s):  
Leila Maria Coelho de Carvalho ◽  
Michelé Dal Toé Casagrande
Keyword(s):  
Shear Strength ◽  
Sandy Soil ◽  
Soil Reinforcement ◽  
Direct Shear ◽  
Shear Strength Parameters ◽  
Shear Tests ◽  
Strength Parameters ◽  
Direct Shear Tests ◽  
Soil Shear Strength ◽  
Curaua Fibers

Inclusion of natural fibers (sisal, curauá, coco fiber and others) for soil improvement has been the study object in diverse geotechnical areas and it is a topic of growing interest, within the research area of new geotechnical materials. The state of the art in this subject highlights excellent results as soil strength parameters improve and post-cracking strength (toughness) increase. Soil reinforcement technique with fibers is established in the technology of composite materials, this being a combination of two or more materials presenting properties that the component materials do not possess on their own. The aim of this paper is to study the mechanical behaviour of sand-fiber composite by inserting natural curauá fibers into a sandy matrix, with different fiber contents. The fibers were randomly distributed in the soil mass. The experimental program included physical and mechanical characterization of the composites, using full-scale direct shear tests, with samples measuring 30 x 30 cm and 15 cm high. Direct shear tests were carried out using fibers with 25 mm length and 0.5 and 0.75% fiber content (relative to the soil dry weight). The specimens also presented a relative density of 50% and moisture content of 10%. It was sought to establish a pattern behaviour so that the addition of curauá fiber influence can be explained, thus, comparing with the sandy soil shear strength parameters. Inclusion of natural curauá fibers as soil reinforcement presented satisfactory results, as an increase in the soil shear strength parameters was observed when compared with sandy soil results.

scholarly journals Study on the Impact of Sand-Clay Bond in Geo-grid and Geo-Textile on Bearing Capacity

2016 ◽  
Vol 9 (6) ◽  
pp. 83 ◽  
Author(s):  
Mohammadehsan Zarringol ◽  
Mohammadreza Zarringol
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Tensile Force ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Increased Strength ◽  
Reinforced Clay ◽  
The Impact ◽  
Total Shear

<p>This paper aims to determine the impact of sand-clay bond in geo-grid and geo-textile on bearing capacity. In doing so, we examined clay-geo-synthetics, sand-geo-synthetics and clay-sand-geo-synthetics samples using direct shear tests. The friction between clay and reinforcement was provided by encapsulated-sand system.</p><p>This method is used to transfer the tensile force mobilized in geo-synthetics from sand to clay and improve the strength parameters of clay. This study indicated that the provision of a thin layer of sand at both sides of the reinforcement significantly improved the shear strength of clay soil.</p>Bond coefficient computations indicated that the shear strength of clay-geo-synthetics samples was higher than non-reinforced clay. The increased strength was due to the impact of open meshes of geo-synthetics which provided some degree of resistance bearing. To determine the share of resistance bearing provided by geo-synthetic transverse members in the entire direct shear strength, we conducted a series of tests on geo-synthetics-reinforced samples with and without transverse members. The resistance bearing provided by geo-synthetic transverse members was almost 10% of total shear strength. The results indicated that encapsulated geo-grid and geo-textile sand system increased the bearing capacity of clay, with geo-grid being more efficient than geo-textile.

In Situ Shear Tests on Masonry Panels Strengthened with Fiber-Reinforced Mortar Repointing

2017 ◽  
Vol 747 ◽  
pp. 282-288
Author(s):  
Nicola Cavalagli ◽  
Massimiliano Gioffrè ◽  
Vittorio Gusella ◽  
Chiara Pepi ◽  
Bernie Baietti ◽  
...  
Keyword(s):  
Shear Strength ◽  
Local Information ◽  
Fiber Reinforced ◽  
Compression Tests ◽  
Shear Tests ◽  
In Situ Tests ◽  
Joint Shear Strength ◽  
Reinforced Masonry ◽  
Diagonal Compression

In this paper the effect of joints structural repointing on single-wythe brickwork masonry using a fiber-reinforced mortar is investigated. Changes in shear strength are evaluated by in-situ tests carried out both on unreinforced and reinforced masonry specimens. The masonry joint shear strength, according to the standard ASTM C 1513, gives local information, while diagonal compression tests provides information on the global masonry shear response. The comparison highlights a good performance in both local and global masonry response, where the shear strength increases.

Interpretation of field vane strength of an anisotropic soil

1992 ◽  
Vol 29 (4) ◽  
pp. 627-637
Author(s):  
Vinod K. Garga ◽  
Mahbubul A. Khan
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Strength Anisotropy ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
State Of Stress ◽  
Anisotropic Soil ◽  
Undrained Shear

Determination of the undrained shear strength (Su) of overconsolidated soils such as the weathered clay crust overlying Leda clay is important for the design of shallow foundations and embankments. In situ vane shear tests and isotropically consolidated undrained triaxial tests have been conventionally used for this purpose. Contrasting test results from these two methods, low Su obtained from triaxial tests and high Su obtained from in situ vane shear tests, motivated further research into this problem. Strength anisotropy, due to in situ anisotropic state of stress and orientation of soil fabric during deposition, is believed to be the reason for these contrasting results. Improved testing and interpretation techniques for this type of anisotropic soil have been proposed. Weathered crusts are generally heavily over-consolidated, with K0 values greater than unity. Undrained triaxial shear tests conducted to date by various researchers are either isotropically consolidated or are anisotropically consolidated assuming K0 smaller than unity. Neither of these two methods represents the in situ state of stress of a clay crust. Therefore, in this investigation, the undisturbed samples were reconsolidated anisotropically to the in situ state of stress (K0 > 1) before shearing undrained in the triaxial test. Direct shear tests on horizontal and vertical specimens consolidated to normal stresses equal to σvo′ and σho′, respectively, were also conducted to investigate the strength anisotropy. Field vane tests have been reinterpreted in terms of this strength anisotropy. The undrained shear strength on top and bottom horizontal planes (Suh) obtained from these field vane tests within the crust provided comparable results with those from laboratory triaxial and direct shear tests which were reconsolidated to in situ stresses. Key words : in situ vane test, undrained shear strength, strength anisotropy, rate effect, anisotropic in situ state, weathered clay crust, overconsolidation.

The influence of aging on the shear strength behaviour of two fine-grained soils

1979 ◽  
Vol 16 (2) ◽  
pp. 391-397 ◽  
Author(s):  
Mehter Mohamed Allam ◽  
A. Sridharan
Keyword(s):  
Shear Strength ◽  
Tangent Modulus ◽  
Black Cotton Soil ◽  
Shear Tests ◽  
Fine Grained ◽  
Shearing Resistance ◽  
Initial Tangent Modulus

A series of undrained triaxial shear tests was conducted on normally consolidated remoulded black cotton soil and kaolinite, in order to examine the influence of aging on their shear strength behaviour. It was found that apart from an increase in shear strength and brittleness, both soils exhibited an increase in their angles of shearing resistance when aged for a month. The cohesion intercept was found to reduce on aging. The initial tangent modulus increases very significantly (to the extent of even 10 times) especially for black cotton soil after 30 days of aging.

Strength of tree roots and landslides on Prince of Wales Island, Alaska

1979 ◽  
Vol 16 (1) ◽  
pp. 19-33 ◽  
Author(s):  
Tien H. Wu ◽  
William P. McKinnell III ◽  
Douglas N. Swanston
Keyword(s):  
Shear Strength ◽  
Root System ◽  
Forest Cover ◽  
Safety Factors ◽  
In Situ Tests ◽  
Tree Roots ◽  
Stability Of Slopes ◽  
Before And After ◽  
The Stability

The stability of slopes before and after removal of forest cover was investigated. Porewater pressures and shear strengths were measured and the soil properties were determined by laboratory and in situ tests. A model of the soil–root system was developed to evaluate the contribution of tree roots to shear strength. The computed safety factors are in general agreement with observed behaviors of the slopes. Decay of tree roots subsequent to logging was found to cause a reduction in the shear strength of the soil–root system.

Determination of the Oldman River Dam foundation shear strength

1991 ◽  
Vol 28 (5) ◽  
pp. 698-707 ◽  
Author(s):  
M. M. Davachi ◽  
B. J. Sinclair ◽  
H. H. Hartmaier ◽  
B. L. Baggott ◽  
J. E. Peters
Keyword(s):  
Shear Strength ◽  
Large Diameter ◽  
Site Investigation ◽  
Bedding Plane ◽  
Plane Shear ◽  
Dam Foundation ◽  
Shearing Resistance ◽  
Oldman River

The paper describes the results of site investigation and laboratory testing and the analysis performed for the determination of foundation shear strength at the Oldman River Dam site in southwestern Alberta, Canada. Horizontally bedded claystones, siltstones, and sandstones at the site contain relatively weak bedding-plane shears that adversely affect foundation stability. Data on the bedding-plane shear characteristics were collected by mapping, borehole coring, shaft exploration, and large-diameter sampling. Shear planes of structure-wide continuity were identified. Numerous laboratory direct shear tests were done to measure in situ and residual shear strengths. The design angle of shearing resistance of selected continuous bedding-plane shears was evaluated by summing the representative residual angle of shearing resistance and components of the angle of shearing resistance due to in situ state, roughness, and thickness of the bedding-plane shears. Relatively flat dam slopes were found to be required for stability. The methods used at the Oldman River Dam should be applicable at other sites located in flat-lying mudrock sequences. Key words: Oldman River Dam, foundation shear strength, sedimentary rocks, bedding-plane shear, residual angle of shearing resistance, in situ state, roughness, thickness.

scholarly journals Influence of Various Gauge Lengths, Root Spacing and Root Numbers on Root Tensile Properties of Herbaceous Plants

2021 ◽  
Vol 50 (9) ◽  
pp. 2499-2510
Author(s):  
Chaobo Zhang ◽  
Xiaoyu Ma ◽  
Yating Liu ◽  
Jing Jiang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Tensile Properties ◽  
Root System ◽  
Tensile Force ◽  
Gauge Length ◽  
Soil Reinforcement ◽  
Root Number ◽  
Power Functions

The mechanical properties of root system play an important role in soil reinforcement by plants. Root tensile properties are affected by many factors. It is necessary to explore the mechanical properties of root system and the influencing factors. In this study, tensile tests were conducted on roots of Kochia scoparia (L.) Schrad and Artemisia sacrorum Ledeb to study root tensile properties, including maximum tensile force, tensile strength and elastic modulus under the three factors, gauge length (50, 100, 150, and 200 mm), root spacing (0, 1, and 2 cm) and root number (single root, double roots, and triple roots). The results showed that the maximum tensile force, tensile strength, and elastic modulus of the roots decreased with increasing gauge length in power functions. Under 100 mm gauge length, the maximum tensile force, tensile strength and elastic modulus decreased with increasing root spacing, but the effect of root spacing considered in this study on the maximum tensile force and tensile strength was not significant. Besides, with increasing root number, the maximum tensile force increased, tensile strength, and elastic modulus decreased. These findings stretched our understanding of the relationship between gauge length, root spacing and root number on root tensile characteristics, and provided the necessary data basis for root tensile properties and soil reinforcement by plants.

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