Foundations on Expansive soils

A review of shale swelling by water adsorption

Soil improvement using biopolymers has attracted considerable attention in recent years, with the aim to reduce the harmful environmental effects of traditional materials, such as cement. This paper aims to provide a review on the environmental assessment of using biopolymers as binders in soil improvement, biopolymer-treated soil characteristics, as well as the most important factors affecting the behavior of the treated soil. In more detail, environmental benefits and concerns about the use of biopolymers in soil improvement as well as biopolymer–soil interaction are discussed. Various geotechnical properties are evaluated and compared, including the unconfined compressive strength, shear strength, erosion resistance, physical properties, and durability of biopolymer-treated soils. The influential factors and soil and environmental conditions affecting various geotechnical characteristics of biopolymer-treated soils are also discussed. These factors include biopolymer concentration in the biopolymer–soil mixture, moisture condition, temperature, and dehydration time. Potential opportunities for biopolymers in geotechnical engineering and the challenges are also presented.

Biopolymers as Green Binders for Soil Improvement in Geotechnical Applications: A Review

This dissertation is based on the study of a new soil nail called screw nail. The research is focused on the design, fabrication and analysis of a new screw nail and its interaction mechanisms between the soil and nail in two cohesive and non-cohesive soi

A study of new screw soil nail

Expansive clay minerals can be a serious threat to underground rock structure because of their swelling behavior when absorbing water. Roof and wall collapse as well as large deformation were observed in Xiaotun Coal Mine, Guizhou Province, China. This paper studies the characteristics of expansive clays in order to understand the mechanism of the mudstone tunnel failures in the mine. The physical and mechanical properties of the tunnel surrounding rock samples, including mudstone, silty mudstone, argillaceous siltstone and fine sandstone were determined. X-ray diffraction analysis was conducted to determine the mineralogical composition while the scanning electron microscope was used to examine the internal structure of the different samples. The results indicate that the illite–smectite and the montmorillonite are the main minerals composing the rock samples. A series of micro-cracks and pores occur in the samples which suggest a good hydraulic conductivity. The results indicate that the mudstone has poorer mechanical properties in comparison to the fine sandstone. Also, the Flac3D numerical simulations were conducted and it was shown that the large deformations were consistent with the field observation due to weak mechanical properties of the surrounding rock under seepage action especially with the increase of water head and porosity. It is concluded that internal structure and mechanical strength of the mudstone is weakened by the illite–smectite and the montmorillonite mineral content as well as the combined action of underground water causing physical disintegration.

Mechanism of the Mudstone Tunnel Failures Induced by Expansive Clay Minerals

Human activity inevitably produces waste materials that must be managed. Some waste can be reused. However many wastes that cannot be used beneficially must be disposed of ensuring environmental safety. One of the common methods of disposal is landfilling. The most common problems of the landfill site are environmental degradation and groundwater contamination caused by leachate produced during the decomposition process of organic material and rainfall. Liner in a landfill is an important component which prevent leachate migration and prevent groundwater contamination. Earthen liners have been widely used to contain waste materials in landfill. Liners and covers for municipal and hazardous waste containment facilities are often constructed with the use of fine–grained, low plasticity soils. Because of low permeability geosynthetic clay liners and compacted clay liners are the main materials used in waste disposal landfills. This paper summaries the important geotechnical characteristics such as hydraulic conductivity, liquid limit and free swell index of geosynthetic clay liner and compacted clay liner based on research findings. This paper also compares geosynthetic clay liner and compacted clay liner based on certain criteria such as thickness, availability of materials, vulnerability to damage etc.

https://iopscience.iop.org/article/10.1088/1757-899X/263/3/032026/pdf

Comprehensive review of geosynthetic clay liner and compacted clay liner

Expansive soils undergo alternate swelling and shrinkage respectively in rainy seasons when they absorb water and in summers when water evaporates from them. Hence, all types of foundations constructed in expansive soils are also subjected to alternate swelling and shrinkage in rainy and summer seasons. As a result, super-structure members are also affected, undergoing severe distress. Various tension-resistant and innovative foundation techniques such as belled piers and under-reamed piles have been devised for arresting the problems posed by expansive soils. Granular pile-anchor (GPA) is a recent innovative technique suggested for expansive clay beds. GPA is quite effective in controlling heave or swelling. Useful experimental heave data were obtained on laboratory scale and field scale GPAs. However, it is also necessary to study the behaviour of GPA-reinforced expansive clay beds subjected to swelling and shrinkage. This paper presents experimental data on shrinkage of GPA-reinforced expansive clay beds. Laboratory scale GPA-reinforced expansive clay beds were subjected to alternate swell–shrink cycles, each cycle for a duration of 300 days. Each clay bed was subjected to three swell–shrink cycles (N = 1, 2 and 3), each cycle monitoring swelling for 10 days and shrinkage for 90 days. The number of GPAs (n) reinforcing the clay beds was varied as 0, 1, 2 and 3. Shrinkage (mm) of a clay bed, recorded in a given swell–shrink cycle, decreased with increasing number of GPAs (n). Further, shrinkage of a given clay bed decreased significantly with increasing number of swell–shrink cycles (N) also. It was also found that shrinkage (mm) of a particular layer in the clay bed decreased with increasing depth (z) of the layer from the top of the clay bed.

Shrinkage Behaviour of GPA-Reinforced Expansive Clay Beds Subjected to Swell–Shrink Cycles

Granular pile-anchor (GPA) technique has been found to be an innovative foundation technique for expansive clays posing the dual problem of swelling and shrinkage. Swelling occurs during absorption of water and shrinkage during evaporation of water. Generally, in field expansive clay beds, swelling takes place during rainy seasons and shrinkage during summers. GPA is a recent innovative foundation technique devised to ameliorate the dual swell-shrink problem of structures founded on expansive clay beds. The other innovative techniques are drilled piers, belled piers and under-reamed piles. Laboratory scale model studies and field scale experiments on GPAs yielded useful results and revealed that swelling of expansive clay beds was effectively controlled by GPA technique. Studies on swell-shrink behaviour of GPA-reinforced clay beds have not been performed so far. This paper presents results obtained from laboratory scale model studies on GPA-reinforced expansive clay beds subjected to alternate cycles of ...

Swelling behaviour of GPA-reinforced expansive clay beds subjected to swell-shrink cycles

The granular pile-anchor (GPA) foundation system, a more recent technique, has also been found to be quite successful in controlling heave of expansive clay beds. This paper presents experimental data obtained from laboratory-scale heave tests conducted on an unreinforced expansive clay bed (n = 0) and expansive clay beds reinforced by a single GPA (n = 1), twin GPAs (n = 2) and a group of GPAs laid in equilateral triangular pattern (n = 3). The thickness of all the test clay beds was 200 mm. Heave was monitored at different depths of clay beds as they were inundated. Ground heave (or surface heave) was also monitored at different radial distances (r) from the centre of the test tank. The unreinforced clay bed and the GPA-reinforced clay beds were identical with regard to thickness (H), placement water content (w%) and dry density (γd). Heave decreased at all depths of the clay beds as the number of the GPAs (n) increased. Furthermore, heave decreased with increasing depth (z) from the top of the clay bed...

Reducing heave of expansive clay beds through granular pile–anchor groups

Granular pile-anchor (GPA) technique is an innovative tension-resistant foundation technique which can effectively ward off the dual swell–shrink problem posed by expansive clays. The other tension...

M. Muthukumar

Papers

Comprehensive review of geosynthetic clay liner and compacted clay liner

Shrinkage Behaviour of GPA-Reinforced Expansive Clay Beds Subjected to Swell–Shrink Cycles

Swelling behaviour of GPA-reinforced expansive clay beds subjected to swell-shrink cycles

Reducing heave of expansive clay beds through granular pile–anchor groups

Influence of wetting–drying cycles on swell–shrink behaviour of GPA-reinforced expansive clay beds