Sand Blocks Research Articles

A Comparison of Conventional Blocks and Stabilized Earth Blocks as Building Materials in Uganda

In Uganda, the high cost of conventional cement and sand blocks has driven the widespread adoption of alternative building materials, such as wattle bricks, compressed earth blocks, and burnt bricks. Among these, compressed earth blocks have gained popularity due to their eco-friendly, energy-efficient, and biodegradable nature. Made by compressing damp soil at high pressure, these blocks offer an environmentally sustainable solution by minimizing deforestation and eliminating the need for firewood, which is often used in the production of traditional bricks. This study employed a case study methodology and utilized deliberate sampling to gather data, which was then analyzed using SPSS v20. The findings revealed that Stabilized Earth Materials (SEMs) have a stronger positive correlation with user satisfaction compared to conventional blocks, with a satisfaction rating of 0.651 for SEMs versus 0.602 for conventional blocks. Additionally, the study showed that SEMs had a notable impact on reducing construction costs, with a 4.8% cost difference in favor of SEMs. Based on these results, it is recommended that construction managers should consider increasing the use of stabilized earth materials. This shift could not only lead to significant cost reductions but also improve the overall quality of construction, making it a more sustainable and viable option for Uganda’s building industry.

Sustainable Production of Building Blocks using A Recycled Plastic Waste

Abstract: Plastic waste is one of the materials that constitutes environmental nuisance and contribute to global warming. The global need to ameliorate the effect of global warming through waste reduction and recycling necessitated this research. The study involved using recycled plastic waste to produce building blocks. The low density plastic waste were collected from dump sites, cleaned and dried before melted and mixed with a fine aggregate at different ratios. The molten slurry formed by mixture of melted plastic waste and fine was poured into the metal mould and allowed to set. The result of the study showed that plastic sand blocks have a compressive strength ranging from 6.8N/mm2 to13.15N/mm2 which has a 3.3% higher than that of normal sand blocks. The water absorption rate, bulk density and Efflorescence results are within the acceptable limits. The exhibition favorable properties of blocks and need for sustainability of our environment should encourage the use of plastic waste produced blocks. This research indicates that bricks produced with plastics exhibit fine surface finishing, low porosity, and light weight, coupled with high compressive strength. Comparatively, these bricks surpass conventional clay bricks in both strength and weight reduction. The study recommends employing bricks produced with plastics for load bearing and framed structures, as well as in wet lands. Additionally, further investigations into different mix ratios are suggested to enhance quality and durability.

Characteristics of wind-sand transportation along railways in the eastern fringe of the Taklimakan Desert and sand control system

Abstract This paper focuses on the Korla-Ruoqiang desert railway line, utilizing ERA5 (ERA5 is the fifth generation of ECMWF (European Centre for Medium-Range Weather Forecasts) atmospheric reanalysis global climate data) wind data to conduct a comprehensive analysis of the wind energy environment along the line in all aspects, reveals the characteristics of wind-sand transport, and puts forward the countermeasures to prevent and control wind-sand disasters. The results of the study indicate that: (1) the wind-sand along the line mainly occurs in the spring and summer seasons, and the dominant sand-moving directions are easterly (ENE, E and NNE) and northeasterly (NE). (2) The average annual sand-moving wind speed ranges from 5.80 m/s to 7.25 m/s, and the annual frequency of sand-moving ranges from 11.99% to 37.26%. (3) The annual sand drift potential (DP) along the line ranges from 69.20 VU to 607.24 VU, with three types of wind energy environments: low, medium and high. The resultant drift potential (RDP) ranges from 45.52 VU to 547.49 VU, and the wind variability index (RDP/DP) is between 0.54 and 0.90. (4) The average sand transport quantity along the line ranges from 2.92 m³/m/a to 9.09 m³/m/a. Based on these results, we optimize the sand blocking, sand fixing and wind erosion prevention measures for different types of wind-sand environments, establish a scientific and efficient wind-sand protection and control system to solve the wind-sand problems and provide a scientific foundation for the prevention and control of wind-sand disasters along the line.

Soil Bacterial Community Structure and Physicochemical Influencing Factors of Artificial Haloxylon ammodendron Forest in the Sand Blocking and Fixing Belt of Minqin, China

Microbial activity plays a crucial role in upholding the functional stability of vegetation–soil ecosystems. Nevertheless, there exists a paucity of studies concerning the impact of sand-fixing vegetation (Haloxylon ammodendron) on the structure and functional attributes of soil microbial communities. We employed Illumina high-throughput sequencing and PICRUSt2 functional prediction technology to investigate the characteristics of soil bacterial community structure, diversity, and metabolic functions in an artificial H. ammodendron forest, and RDA analysis and the Mantel test were used to reveal the main environmental factors affecting the structure and ecological functions of soil bacterial communities. The findings revealed a significant increase in the principal nutrient contents (organic matter, total nitrogen, total phosphorus) in the H. ammodendron forest soil compared to the mobile dune soil, while a reduction of 17.17% in the surface soil water content was observed. The H. ammodendron forest exhibited a significant enhancement in the diversity and richness index of soil bacteria. Specifically, Actinobacteria (24.94% ± 11.85%), Proteobacteria (29.99% ± 11.56%), and Chloroflexi (11.14% ± 4.55%) emerged as the dominant bacterial phyla, with Actinobacteria displaying significantly higher abundance compared to the mobile dune soil. PICRUSt2 analyses revealed that the predominant secondary metabolic functions of soil bacteria were carbohydrate metabolism, amino acid metabolism, and the metabolism of cofactors and vitamins. Additionally, the tertiary metabolic pathways exhibited greater activity in relation to enzyme function, nucleotide metabolism, energy metabolism, and antibiotics. The RDA results demonstrated that SOM, AK, and pH collectively accounted for 82.4% of the cumulative contribution, significantly influencing the bacterial community. Moreover, the Mantel test revealed that the metabolic function of soil bacteria primarily relied on five environmental factors, namely SOM, TN, AK, pH, and EC. This study significantly advances our understanding of the structural and functional changes in soil bacterial communities during the reclamation of sandy land through the establishment of artificial H. ammodendron forests.

Numerical Simulation and Parameter Optimization of a New Reed–Nylon Net Combined Sand Fence

This paper introduces a kind of double-row reed–nylon net combined sand barrier. Using the computational fluid dynamics (CFD) method and the Euler–Euler double-fluid model, the new sand fences’ windproof effect and airflow features are simulated under different porosities and spacings, and the optimal configuration parameters are selected. The new sand fence has better windproof performance and practical significance than double-row reed and double-row nylon net fences. The new sand fences with a porosity of 0.3–0.4 and spacing of 28 H provide a longer protection range and a better wind protection effect. Considering the serious sand damage in China’s Taklamakan Desert, the new fences’ impact on sand buildup is examined. The combined sand fences have powerful sand blocking and accumulation effects, even though there is only a small quantity of sand accumulation on the leeward side of the second row. The sand particles primarily settle between sand fences in the center and rear areas. The combination of sand fences made of different materials combines the advantages of both, improves the construction efficiency and service life, and provides a more economical and efficient sand barrier arrangement for the arrangement of wind and sand-blocking facilities around railroads and highways in desert areas.

Experimental Study on Mechanical Properties and Drying Shrinkage Compensation of Solidified Ultra-Fine Dredged Sand Blocks Made with GGBS-Based Geopolymer

As natural aggregates become increasingly scarce, attention has turned to ultra-fine dredged sand (UDS) generated in waterway regulation engineering. UDS is typically challenging to utilize due to its high clay content and high water demand. This article uses ground granulated blast-furnace slag (GGBS)-based geopolymer to solidify UDS, along with sodium silicate (SS) and sodium hydroxide (SH) as alkaline activators. This paper explores the effects of SS modulus (SiO2/Na2O molar ratio) and mass percentage content of Na2O on the fluidity, setting time, mechanical properties, and shrinkage behavior of hybrid UDS-GGBS geopolymer (HUGG) paste. According to the research findings, increased SS modulus and Na2O content lead to decreased fluidity and setting time. When the Na2O content reaches 6%, flash coagulation occurs in the slurry, leading to more internal shrinkage cracks and pores. This has been confirmed by scanning electron microscope (SEM) analysis. When Na2O content is 5%, and SS modulus is 1.0, the 90-day maximum compressive strength reaches 56.53 MPa, corresponding to a splitting tensile strength of 6.83 MPa, which can be considered the optimal formulation. Meanwhile, basalt and polypropylene fibers (BF and PPF) are chosen to compensate for the susceptibility to drying shrinkage. Both BF and PPF can significantly inhibit the linear drying shrinkage of the HUGG paste. The BF’s ability to enhance mechanical properties is more robust than PPF’s, which can make the paste more homogeneous. The research contributes an effective method for the resource utilization of UDS.

Optimization Study on the Design Parameters of Sand Barriers along the Hami-Lop Nor Railway Line

In order to solve the current problems of the single effect of traditional sand control measures, the high cost of cleaning and maintenance, and the inability to provide long-term sustainable protection, this paper proposes a new type of sand barrier with the dual effect of sand conduction and sand blocking. Through field research of wind and sand disasters along the Hami-Lop Nor Railway, wind tunnel testing and numerical simulation of the new sand barrier, the wind velocity flow field, wind speed variation curve, wind protection effectiveness and sand barrier retention rate of the new sand barrier under different design parameters were studied. The results show that the sand barrier with 10H spacing (H is the height of the sand barrier) has the worst sand guiding and blocking effect. The sand barriers with 6H and 8H spacing have less difference in sand guiding and sand blocking effects. Both of them are better than the sand barrier with 10H spacing. The sand blocking effect of the new sand barrier was proportional to the angle (α). The sand guide effect was the opposite. When the angle is certain, the greater the wind speed and the better the sand guide effect. The results show that the new sand barrier is different from the traditional sand barrier in that it has both sand guiding and sand blocking functions, which provides a new method and scientific basis for sand damage control of Hami-Lop Nor Railway.

Pattern and Analysis of Corrugation-Sand Retaining Seals for Tooth Wheel Drill Bits

The existing seal is not designed with a special sand retaining structure, and it is difficult to discharge the mud particles after entering, resulting in serious wear of the seal and premature failure. Therefore, a special-shaped sealing structure for sand blocking of roller cone bits is proposed to solve the problem of sealing wear. Starting from the structural principle, the structural parameters of the special-shaped seal of the sand-retaining flap are designed based on the O-ring, and the sealing principle is analyzed, the formula of grease leakage is derived, and the simulation and optimization analysis are completed with the aid of APDL. This proved the feasibility of the design. The influence law of structural parameters on contact pressure and leakage is obtained, and the formula of leakage is verified; The influence of structural parameters on the contact gap of the sand flap is obtained. Under the condition of optimal combination of structural parameters, the grease leakage is 43 mg/h, a decrease of 85%. Theoretically, it takes 580 h to exhaust the grease, and the contact gap of the sand flap is 0.00019479 mm, a decrease of 95%, which can greatly reduce the wear of the main seal. This study opens up a new idea for seal design.

Effect of Wet Condition and Aggregates Type Used in Cement-Based Blocks on Mechanical Behavior of Masonry

Water penetration into masonry walls can occur in the masonry structures during the rainy climate. Water penetration not only causes discoloration or efflorescence but also can be damaging to material property. Eventhough several studies from past literature focus on wet conditions effect on brick masonry, but there is limited study on cement block masonry. The present research aimed to evaluate the effect of wet conditions on the mechanical characteristic of cement block, binder mortar and masonry. Where three types of fine aggregates, namely river sand, lateritic soil and manufactured sand were used for masonry block production. For binding mortar, two mortar classes M2 and M6 according to British Standard European Norm were used. Compression, flexural bending, and splitting tensile tests for blocks and binding mortar were performed in dry and wet conditions. Also, compression, direct shear and bond test were performed on masonry prisms in dry and wet conditions. The results demonstrate that a considerable amount of strength reduction was observed in wet conditions. In wet conditions, cement-soil block masonry showed a higher reduction in compression strength and bond strength, but showed lesser shear strength reduction when compared with the other two masonry types. Overall, cement-river sand block masonry has shown better performance in wet conditions.

Sand control effect of HDPE sandbreak nets with different porosity structure

Straw checkerboard sand barriers with a porous structure that consists of a pervious upper portion and a dense lower portion are widely used to achieve great sand control effect. Considering this, and resolving the serious earth surface undercutting problem after HDPE sandbreak net checkboard barriers setting, the authors used HDPE (high-density polyethylene) materials to prepare new sandbreak materials with a similar porous structure. Through wind tunnel simulations and field sand control monitoring, we compared the sand control effect of three HDPE sandbreak nets with different porosity structure. Compared to the sandbreak net with uniform porosity structure, the three types of HDPE sandbreak nets with different porosity structure had poorer effect on reducing sand transport rates, but had longer effective protection distance before sandbreak nets at low wind velocity conditions (<12 m/s), longer effective protection distance at high wind velocity (>14 m/s) and longer effective protection distance between sandbreak nets at all experimental wind velocity conditions. Wind and sand control effect characteristics of HDPE sandbreak nets with different porosity structure provide an ideal material on semi-buried checkerboard sand barriers for sand stabilization. By contrast, uniform-type sandbreak nets are used as materials on high upright sand fences for sand blocking. These HDPE sandbreak nets can be used to replace traditional sandbreak materials and have a very high potential for widespread and popular application in aeolian sand disaster control.

Seawater based bio-cementation for calcareous sand improvement in marine environment

Seawater based bio-cementation through microbially-induced carbonate precipitation was proposed for the calcareous sand improvement in marine environment. The method used seawater instead of traditional fresh water to culture urease producing-bacteria (UPB) and prepare cementation solution (CS) for the bio-cement. A series of comparative bio-treatment tests using seawater based bio-cementation and traditional bio-cementation methods on three types of soil were conducted. Experimental results indicate that seawater based bio-cementation method has the ability to improve soil physico-mechanical properties, and performed better than traditional bio-cementation method. The dominant reason can be explained as that the mixture of the productions of calcite, monohydrocalcite and calcite magnesium produced during seawater based bio-cementation process have better cementation ability than the mixture of the productions of calcite and vaterite produced during bio-cementation process. UCS of coarse Ottawa sand blocks are smaller than that of medium Ottawa sand blocks is because the specific surface area of fine sand is higher and larger number of effective bondings can be formed. UCS of calcareous sand blocks are smaller than those of coarse Ottawa sand blocks can be attributed to the fact that calcareous sand has higher porosity and rougher surface, resulting in more carbonate crystals being precipitated on un-connected locations.

Experimental study on sand control gravel particle gradation optimization in mud hydrate reservoir

Sand production significantly influences the safety and stability of gas hydrate exploitation in reservoirs with high mud content. Gravel packing is an effective method for sand control. The median grain size ratio (D50/d50) values and fine particle content of gravel pack are important factors in sand control during natural gas hydrate exploitation. This paper focuses on the sand blocking effect and permeability characteristics of different grades of gravel. The sand retention test was carried out on four samples with different ratios. The optimal D50/d50 value and fine particle content for gas hydrate production were obtained. A laser particle size analyzer and geotechnical test found the reservoir and gravel layer pore structure change. The results show that the optimal GSR was 24.5, and the optimal fine particle content was about 38%. The permeability decline of the gravel layer occurs in the early stage of production, and the fine particles in the gravel will slow down the degree of seepage damage. For gravel with the same particle size range and different median particle sizes, it has little effect on sand control accuracy but mainly on permeability. The research in this paper can provide a reference for selecting sand control gravel for natural gas exploitation in marine areas.

Experimental Study on the Permeability Damage Mechanism of Gravel Pack Sand Control Medium in Mud Hydrate Reservoirs

Yu, L.; Han, Z.; He, J., and Li, G., 2022. Experimental study on the permeability damage mechanism of gravel pack sand control medium in mud hydrate reservoirs. Journal of Coastal Research, 38(6), 1104–1115. Coconut Creek (Florida), ISSN 0749-0208. The high argillaceous gas hydrate reservoir contains high silt and fine sand content. During the mining process, the fine silt sand will cause blockage of the gravel sand control medium, resulting in reduced medium permeability, that is, penetration damage. Penetration damage will reduce productivity and affect the long-term effectiveness of gravel. For the penetration damage problem of gravel sand control medium, the sand blocking simulation experiment of different reservoir water content, experimental pressure, and gravel specifications were carried out by self-developed sand blocking experiment system. A laser particle size analyzer and electron microscope were used to measure and observe the deposition of sand particles in the upper, middle, and lower layers of gravel layer after the sand retention experiment. The law of permeation damage and the mechanism of media permeation damage were summarized. The research results show that the blockage of sand control media can be divided into four stages: the beginning of blockage, the intensification of blockage, the dredging of blockage, and the balance of blockage. Reservoir water content, experimental pressure, and gravel size all influence permeability damage of gravel. The primary and secondary relationship of the influence of these factors on permeability damage is gravel size, experimental pressure, and reservoir water content. The pressure mainly affects the invasion depth of reservoir sand. The reservoir water content mainly affects the degree of permeability damage. The optimum particle size median ratio D50/d50 is about 25, and the medium has strong antipermeability damage ability and good sand retaining effect.

INVESTIGATION OF WELLS IN THE WORKING FUND OF “AZNEFT” PU AND PROPOSAL OF ANTI-SAND MEASURES

INVESTIGATION OF WELLS IN THE WORKING FUND OF “AZNEFT” PU AND PROPOSAL OF ANTI-SAND MEASURES

Study on High-Resolution Suspended Sediment Distribution under the Influence of Coastal Zone Engineering in the Yangtze River Mouth, China

In this study, we analyzed the influence of coastal zone engineering on suspended sediment concentration (SSC) in the Yangtze River mouth based on HY-1C and Chinese GaoFen (GF) satellite data. The results show that: (1) SSC in the Yangtze River mouth is mainly in the range of 200–1300 mg/L, which changes due to natural factors as well as coastal zone engineering; (2) The sand blocking engineering effectively protects the channel from siltation, and SSC in the central line of the channel is 100–300 mg/L lower than that near the dikes in the north and south; (3) Qingcaosha Reservoir plays a stabilizing role in the hydrodynamic force, promoting the deposition of suspended matter, so that the water in the reservoir is clear. SSC inside the Qingcaosha Reservoir, located in the center of the estuary, is 100–500 mg/L lower than the high SSC water outside the reservoir; (4) The bridges interact with the current, facilitating the transport of local sediment, resulting in the increase in SSC downstream of these bridges, and obvious vortexes appear with the length up to nearly 2400 m; and (5) Corresponding protection and development suggestions were put forward as follows. A linear array of wind power plants can be built near and parallel to dikes and leading jetties; to increase the depth of the southeast end of the reservoir; and the location of the bridge should be selected in the place of river where siltation is easy. This study aimed to study the SSC distribution under the complex impact of coastal zone engineering with satellite and to provide possible improvement suggestions.

Seawater based MICP cements two/one-phase cemented sand blocks

The Sporosarcina pasteurii strains can grow and multiply in seawater medium and have certain urease activity. The two-phase and one-phase cementation methods can be used for the construction of ocean islands and reefs far away from the mainland in seawater seawater based MICP (Microbial-Induced Carbonate Precipitation). The compressive strength, carbonates content and porosity of sand blocks cemented by seawater based MICP with two-phase and one-phase methods are measured and compared. The results show that the strength and carbonates content of sand blocks with two-phase biocementation are greater than that of one-phase. The SEM images show that the principle of seawater based MICP cementing loose sand blocks is that carbonates particles grow between the sand particles, and them act as a bridge to bind the loose sand particles into a whole. The seawater based UPB of different pH can induce calcium carbonate deposition at different time. The seawater based UPB of different pH can be selected according to the actual project to reinforce the island reef sand foundation and prepare building materials under one-phase biocementation.

Effect of Desiccation on the Hydraulic Conductivity of Compacted Bentonite–Sand Blocks

This study investigated the impact of drying cracks on the hydraulic conductivity of compacted bentonite–sand blocks to support the construction of buffer barriers in an underground research laboratory for the disposal of China’s high–level radioactive waste. The hydraulic conductivity of an air-dried block (the worst storage case) was measured in a flexible–wall permeameter in the directions parallel and perpendicular to the direction of compaction according to ASTM D5084. The results were compared with the hydraulic conductivity of fresh blocks. Computerized tomography (CT) images were used to visualize the internal cracks of the blocks, and the swell index was measured to represent the blocks’ swelling properties. The test results revealed that compared with fresh blocks, the drying cracks increased the hydraulic conductivity of the blocks by less than fourfold. As demonstrated by the CT images, the drying cracks were healed after permeation with distilled water. The swell index of the block was unaffected by air drying, and the swelling of montmorillonite in bentonite contributed to the healing of the drying cracks.

Ranking of walling materials using eco-efficiency for tropical climatic conditions: A survey-based approach

All over the world, “Construction” is an important sector that consumes a significant amount of resources and produces a lot of waste. Buildings as a whole share nearly one-fourth of total electricity generation in tropical countries that results in adverse effects on the natural environment and their national economies. Enhancing the building energy efficiencies relies on material and technology selection that complement the local climatic conditions. Compressed Stabilized Earth Blocks are considered as an innovative and proven building envelope upgrade that enhances building efficiencies both economically and environmentally considering their cradle-to-gate phase. However, the cradle-to-grave life cycle impacts of Compressed Stabilized Earth Blocks compared to conventional walling materials are yet to be assessed in tropical climatic conditions for long-term decision making. Accordingly, the objective of this study is to compare compressed Stabilized Earth Blocks with conventional walling materials such as Burnt Clay Bricks and Cement Sand Blocks. The life cycle thinking approach was integrated with eco-efficiency analysis to compare and evaluate the above-mentioned materials considering their entire life span from cradle to grave. Accordingly, Compressed Stabilized Earth block has been selected as the more efficient material with environmental benefits. Moreover, since it can be used as a walling element even without the application of plaster, costs and environmental impacts could be further reduced when used without plastering. The findings of this research will encourage building developers, contractors, and practitioners in selecting the most desirable material for their projects considering costs and environmental impacts of the material life cycle.

Sand Blocking Mechanisms and Productivity Analysis of Slant Well in Siltstone Reservoirs

The siltstone reservoir with many small layers of pay zones is usually produced by slant holes. However, severe sand blockages take place when the siltstone reservoir is developed by slant holes. Currently, the sand blocking mechanisms and the effect of sand blocking on productivity of slant well are still challenges for engineers and scholars. In this paper, based on the existing productivity model of inclined slant wells, the mechanical skin factor, which describes the effect of sand blocking on productivity, is proposed. Meanwhile, many experimental works have been done to investigate the sand blocking mechanisms in siltstone reservoirs. From the experimental work, it is concluded that with the increase of displacement PV number and displacement flow rate, the permeability of sand control system decreases by 40%. When solid particles enter the casing and block the gravel and sand control screen in the annulus, the skin factor increases sharply and the productivity decreases by more than 80%. Through the productivity calculation of multilayer sand control wells, it is considered that larger gravel packing radius can keep particles away from the well bore, which is helpful to ensure oil well productivity. Furthermore, the influence of differential filling radius on the fluid production capacity of each layer of sand control well is analyzed. It is proved that optimizing the filling radius of each layer can improve the production effect of mediate- and low-permeability layers. This method has been applied in Kendong #12 block. The daily oil production rate is increased by 9.61 t/day, and the oil recovery of this block is increased by 2.12%.

The Effect of the Modular Block Type on Segmental Walls in Soil Reinforced by Geogrid

The behavior of retaining walls in geosynthetic reinforced soil is complex and requires studies and research to understand the mechanisms of rupture, the behavior of the reinforcements in the soil and the behavior of the main elements of the system: reinforcement-wall-soil. Several researches have been done on the use of geosynthetics as backfill massive reinforcement material (experimental studies, numerical analysis, reduced models …). This parametric study was conducted to investigate the influence of modular blocks type on the behavior of reinforced soil segmental walls. A 3.6 m high wall is composed of modular blocks of earth sand reinforced with four geogrid layers was modeled. The properties of materials, the wall geometry, and the boundary conditions will be explained later. The finite difference computer program FLAC3D was used in this study. The results of this numerical study allowed deducing the importance of this parameter. The type of modular blocks has significant effect to decrease the values of lateral displacements of the wall and decreased tensile stress values in the layers of geogrid.