Reusing waste plastic can be considered as an important issue in terms of economical as well as environmental concerns. Stabilization of clayey soil is a well-utilized approach to improve the mechanical properties concerning the geotechnical aspects. Meanwhile, the effect of concurrent employment of both lime and waste plastic fibers with different contents and various shapes on mechanical properties of clay is not evident. This research presents the mechanical characteristics of clayey soil reinforced with Plastic Polyethylene Terephthalate (PET). Both unstabilized and lime-stabilized clay are considered as unreinforced materials and the plastic strips and pellets are separately utilized as reinforcement substances. Various tests namely standard Proctor compaction test, point load test (PLT) and drop-weight impact loading test are performed to assess the effect of reinforcement and stabilization on mechanical behavior of clayey soil. The concurrent influences of using PET and adding lime confirm that positive effect of lime stabilization on strength is more meaningful. Meanwhile, the limited content of 1.5% of PET shows the maximum strength for reinforced clayey soil. Generally, reinforcement with strips leads to the exhibition of higher strength based on the point load strength index and more flexibility based on the applied impact loads in comparison with pellet particles. 

Mechanical Properties of Clayey Soil Reinforced with PET Considering the Influence of Lime-Stabilization

The swelling characteristic in soil and rock mass is recognized due to presence of clay minerals such as montmorillonite and anhydrite. However, this swelling feature does not pose a threat to the engineering structure until physico-chemical reaction with water takes place. In this case, stability of engineering structure is jeopardized due to volume and swelling stress increase. Long routes of tunnels excavated in different geological rock formations increase the probability of failure as tunnels pass through swelling soils or rocks. Tunnels are the most affected engineering structure from swelling problems as a result of their long service life. The Terzili tunnel, which is the subject of this article, is double-tube and 1180 m long and cuts the swelling geological units along its route. It passes through a flysch and clay unit consisting of alternation of conglomerate-sandstone-claystone. Claystone has a swelling property and its maximum swelling stress range between 0.77 and 2.0 MPa; the maximum swelling deformation ranges from 5.97 to 9.75%. After some excavation has been made from the entrance and exit parts of the right and left tubes in the Terzili’s tunnel, the advance in the tunnel has stopped. After 17 months, cracks were observed on the 2-m thickness invert concrete as a result of swelling stress. As a remediation, it was decided to reinforce 40 cm thick steel reinforced concrete slab on the existing filling concrete, depending on the thickness of the superstructure. In the numerical modeling, Phase2 program does not have a module to model the effect of swelling minerals included clay units, directly. Swelling effect in models was created by applying additional distributed load to the tunnel support. In addition, to model umbrella arch effect, the impact zone of the umbrella arch has been created as a new material. For section 1 of the tunnel, in the case where the swelling pressure is 0.5 MPa, the maximum principal stress and displacement around the tunnel are 2.5 and 9 times, respectively, compared to the non-swelling pressure. For section 2 of the tunnel, the calculated values are 1.3 times of the maximum principal stress and 21 times of the displacement if there is 0.5 MPa swelling pressure.

Stability assessment of Terzili tunnel in swelling rock mass

This paper evaluates the suitability of sugarcane bagasse ash (SCBA) and waste marble dust (WMD) on the geotechnical properties of Palygorskite-rich expansive clays located in northwest Pakistan. These problematic soils exhibit undesirable characteristics which greatly affect the pavements, boundary walls, slab-on-grade members, and other civil engineering infrastructures. A series of geotechnical tests were performed on soil specimens using prescribed percentages of the aforementioned Ca-based stabilizer materials (CSMs). The investigation includes X-Ray Diffraction (XRD) Analysis, Scanning Electron Microscopy (SEM), X-Ray Fluorescence (XRF) tests, and physicomechanical properties such as moisture-density relationship, Atterberg’s limits, swell pressure, and an ANN-based sensitivity analyses of overall swell pressure development. The outcomes of these experimental investigations showed that the addition of CSMs into the expansive soils increased to 4% SCBA and 10% WMD, the plasticity index reduced by 30% and 49%, the volumetric swell decreased from approximately 49% to 86% and 63%, and the swelling pressure reduction was from 189 kPa to 120 kPa and 160 kPa (about 15% and 36%), respectively. It is interesting to note that replacement with specified CSM accelerated the strength of soil at extended curing periods and the optimum improvement in the strength behavior of the soil was also recorded. Moreover, with addition of the respective CSMs, the compactability and strength characteristics were ameliorated, while plasticity was significantly lowered. Given the amount of SCBA and WMD produced annually, their utilization for the stabilization of problematic soils, even in relatively low concentrations, could potentially have a substantial impact on the sustainable reuse of these waste materials.

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Isolated Effect and Sensitivity of Agricultural and Industrial Waste Ca-Based Stabilizer Materials (CSMs) in Evaluating Swell Shrink Nature of Palygorskite-Rich Clays

Coffee is currently one of the most prized food commodities. Its production has grown so much in recent times, however, the waste by-products generated are also huge. It is envisioned that with rapid urbanization and construction, the use of these by-products can offset the demand for construction materials such as cement and concrete. It is now generally accepted that the manufacture of cement and concrete reduces the supply of natural aggregates at the same time generates carbon dioxide emissions and deteriorates the environment. In this paper, the sustainable use of coffee husk ash (CHA), produced from coffee production is discussed. The CHA necessitates huge land for storage and is normally then left in site locations where it is first dumped, while others are burned in incinerators, contributing to air pollution, thus creating a significant environmental issue. This article will first focus on general coffee production, consumption, and waste by-products. Its life cycle from plantation to wastes is then discussed followed by the effective usage of CHA for the production of ceramics and use in soil stabilization. The article summarizes the use of CHA in soil stabilization and examines development patterns in terms of strength and durability. The findings indicate that adding CHA into soil stabilization benefits both sustainability and zero-waste technologies. • Assessing the usage of coffee husk ash (CHA) in soil stabilization. • The production, consumption, waste usage, and environmental concern of CHA are all explored. • The physicochemical characteristics of CHA used in construction material are described. • Insight into the present CHA potential and state of the art is discussed. • Adding CHA as soil stabilization material benefits both sustainability and zero-waste technologies. 

Utilization of coffee husk ash for soil stabilization: A systematic review

Geospatial and statistical interpolation of geotechnical data for modeling zonation maps of Islamabad, Pakistan

Presence of swelling soils in the foundations may cause excessive damage to the buildings, pavements and other lightweight structures due to its differential volume changes with the moisture. On the other hand, some of the massively generated industrial wastes offer engineering characteristics, which may be utilized with a twofold benefit of cleaned environment and soil stabilization. In this study, silica fumes and scrap rubber powder from local industry have been mixed with a highly expansive soil in different proportions to improve its strength and deformation characteristics. Furthermore, scanning electron microscope images were studied to understand the effects of additives on the stabilization mechanism of the expansive soils. The analyses of results confirmed that these industrial wastes could markedly improve the undrained shear strength and sufficiently decrease the swelling characteristics of tested soil. A set of empirical correlations have also been proposed to predict both swell potential and pressure that could be subsequently verified through additional experimental data obtained from additional published studies. In essence, the proposed empirical correlations could predict the behaviour of the tested additional data with a standard error of mean well within ±10% that may be suitable for preliminary assessments of most practical sites.

Laboratory modelling of strength and deformation characteristics of a high swelling soil treated with industrial wastes

Geotechnical characterization and statistical evaluation of alluvial soils of Lahore

Predicting the susceptibility of rockfall mountain hazards for block-in-matrix soils is challenging for critical steep cuts. This research illustrates a hydrogeotechnical approach for the prediction of rockfall triggering by performing laboratory tests on low-cohesive-matrix soil collected from steep slopes with 85° to 88° angles at the Tatta Pani site, Karakorum Highway (KKH), and then real-scale moisture-induced rockfall was conducted on site for the validation of laboratory data. Laboratory data of forty quick direct shear tests on samples collected from the field depicted a 3-fold drop in peak shear stress (PS) at the soil–soil interface and a 9.3-fold drop at the soil–rock interface by varying the moisture content from 1% (taken as dry phase) to a critical laboratory moisture content (MC)LC of 21% (taken as wet phase). Similarly, a drop in the elastic modulus (ES) was observed to be 5.7-fold at the soil–soil interface and 10-fold at the soil–rock interface for a variation of moisture content from 1 % to 21% for the matrix with a permeability (k) range of 3 × 10−4 to 5.6 × 10−4 m/s, which depicts the criticality of moisture content for the rockfall phenomenon. The critical moisture content evaluated in laboratory is validated by an innovative field-inundation method for thirty-two moisture-induced real-scale forced rockfall cases, which showed the rock-block triggering at field dry density (γd)f and the critical field moisture content (MC)FC of the matrix ranging from 1.78 g/cm3 to 1.92 g/cm3, and 1.3% to 25.4%, respectively. Hydrogeotechnical relations, i.e., MC versus PS and ES, at the soil–rock interface are developed for the prediction of rockfall triggering. The proposed correlations may be helpful in the prediction of rockfall hazards by using expected rainfall in the field for disaster warning and landslide disaster prevention at ecological geotechnical engineering projects. The results revealed that the critical (MC)FC and (MC)LC are within 20%, depicting a good confidence level of the outcomes of this research.

https://www.mdpi.com/2071-1050/14/24/16740/pdf?version=1670996484

Hydrogeotechnical Predictive Approach for Rockfall Mountain Hazard Using Elastic Modulus and Peak Shear Stress at Soil–Rock Interface in Dry and Wet Phases at KKH Pakistan

Imtiaz Rashid

Papers

Laboratory modelling of strength and deformation characteristics of a high swelling soil treated with industrial wastes

Geotechnical characterization and statistical evaluation of alluvial soils of Lahore

Hydrogeotechnical Predictive Approach for Rockfall Mountain Hazard Using Elastic Modulus and Peak Shear Stress at Soil–Rock Interface in Dry and Wet Phases at KKH Pakistan