Search Results (8)

In order to address the challenges of soft coal texture, poor permeability, and wellbore instability in tectonic coal reservoirs, a new biodegradable fuzzy-ball drilling fluid combined with a bio-based surfactant and enzyme system was developed. The optimal formula was determined through single-factor experiments and orthogonal optimization: 6% KCl–2% trehalose composite base slurry + 4% carboxymethyl chitosan + 0.4% hydroxypropyl methylcellulose + 0.15% xanthan gum + 0.12% guar gum + 0.3% cocamidopropyl betaine + 0.15% lauryl alcohol + 0.2% triethanolamine, with the degrading agent consisting of 0.2% composite-modified amylase + 0.04% composite-modified cellulase. The performance evaluation results show that the drilling fluid has stable rheological properties in the temperature range of 40~60 °C (yield point-plastic viscosity ratio: 0.8~0.9) and low filtration loss (5.8~6.5 mL); it exhibits excellent inhibition on tectonic coal, the inhibition rate of linear expansion rate is 72.1%, and the 14-mesh rolling recovery rate is 82.5%; at 55 °C, the gel breaking rate reaches 96.9% after 1.5 h, the mud cake removal rate reaches 98.8%, and the permeability recovery rate reaches 84.8%. After applying this drilling fluid, the unconfined compressive strength of tectonic coal increases from 1.2 MPa to 2.8 MPa (an increase of 133.3%), and the triaxial compressive strength increases from 20.1 MPa to 38.5 MPa (an increase of 91.5%); the numerical simulation shows that the radial displacement around the wellbore decreases by 62.1% and the plastic zone area shrinks by 73.2%. This novel biodegradable fuzzy-ball drilling fluid has the characteristics of efficient wellbore stabilization, easy degradation, and low formation damage, providing effective technical support for the green development of coalbed methane in tectonic coal reservoirs. Full article

The risk of environmental accumulation of aluminum ash and red mud is increasing, emphasizing the demand for high-value utilization. In this study, the conversion of aluminum ash and red mud into porous refractory materials with good thermal insulation performance is successfully demonstrated, demonstrating that both residues can be recovered as a resource and their environmental impact can be reduced in a sustainable manner. The phase composition and microstructure of the waste are evaluated by XRD and SEM/EDS, respectively, while their high-temperature behavior and performance were assessed through visual high-temperature furnace testing. The influence of the aluminum ash-red mud ratio on the rheological behavior of slurries containing surfactants at a constant alkaline pH was highlighted. A slurry composition of 40% red mud and 30% aluminum ash exhibited the lowest shear stress and viscosity values, required to facilitate bubble growth. Building on this formulation, foaming with 2% (mass fraction) H₂O₂ at 80 °C and sintering at 1250 °C produces a material with the optimum performance: a compressive strength of 1.03 MPa, a porosity of 58.55%, and thermal conductivity of 0.19 W/(m·K). The material exhibits long-lasting stability at temperatures ≤ 1100 °C. Thus, complementary compositions of aluminum ash and red mud show potential for practical application and value addition in the preparation of porous refractory materials with thermal insulation properties. Full article

In long-distance, large-section rectangular pipe jacking operations, machine deviation is an inevitable factor that poses substantial challenges to the accurate prediction of frictional resistance. To address this issue, a novel methodology is proposed to analyze the dynamic interactions at the pipe–soil–slurry interfaces. This approach integrates real-time alignment monitoring with the Winkler elastic foundation theory to enhance predictive accuracy. A comprehensive predictive framework is developed for excavation profiles and pipeline deflection curves under varying thrust distances, enabling the quantification of complex contact states. By applying Newton’s law of friction and the Navier–Stokes fluid mechanics equations, calculation methods for the frictional resistance of pipe–soil contact and pipe–mud contact are systematically derived. Furthermore, a predictive model for the jacking force in long-distance rectangular pipe jacking, accounting for complex contact conditions, is successfully established. The jacking force monitoring data from the 233.6-m utility tunnel pipe jacking project case is utilized to validate the reliability of the proposed theoretical prediction method. Parametric analyses demonstrate that doubling the subgrade reaction coefficient enhances peak resistance by 80%, while deviation amplitude exerts a 70% greater influence on performance compared to cycle parameters. Slurry viscosity emerges as a critical factor governing pipe–slurry interaction resistance, with each doubling of viscosity causing up to a 56% increase in resistance. The developed methodology proves adaptable across five distinct operational phases—machine advancement, initial jacking, stable jacking, deviation accumulation, and final jacking—establishing a robust theoretical framework for the design and precision control of ultra-long pipe jacking projects. Full article

In order to address the issue of hole collapse, which frequently arises when boring piles are being constructed in intricate marine strata, this paper discusses the influence of the slurry ratio on the slurry performance as well as the mechanism of slurry wall protection. It performs this by means of theoretical analysis, laboratory ratio testing, engineering analogies, numerical simulation, and field testing. Our findings demonstrate that adding sodium polyacrylate and sodium carboxymethyl cellulose can enhance mud’s viscosity, contribute to flocculation, and improve the connection between mud and soil layers. Refering similar engineering cases, three optimization schemes are proposed for achieving a mud ratio that offers wall protection in complex marine strata. Furthermore, the particle flow model of slurry viscous fluid is established. The collapse of holes in the sand layer is reflected in the uneven radial displacement of hole walls and the invasion of mud particles. Increasing the viscosity of mud gradually transforms the uneven radial deformation of pore walls in the sand layer into a uniform radial deformation, whereas increasing the proportion of mud significantly decreases the radial displacement of hole walls. Additionally, when the mud pressure in the hole is 300 kPa and 600 kPa, the wall protection effect is better, and there is no particle penetration by substances such as sand. It is found that a high mud pressure can promote the diffusion of mud particles into the sand layer, while low mud pressure cannot balance the pressure on deep soil. The results of the field tests show that the ratio of water–clay–bentonite–CMC-Na–sodium carbonate = 700:110:90:1.5:0.5 used (where the mass percentage of each material is 77.8% water, 12.2% clay, 10% bentonite, 0.16% CMC-Na, and 0.05% sodium carbonate) can effectively prevent hole collapse and reduce the thickness of the sand layer at the bottom of the hole by 50%. Full article

Conventional fluid loss additives have difficultly controlling the water loss of cement–metakaolin slurry with semi-saturated brine cement slurry and limiting it to less than 50 mL (30 min)⁻¹. This paper describes the development of an anti-salt fluid loss additive for metakaolin–cement systems. This study adopted the aqueous solution polymerization method; selected four kinds of monomers, namely 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), N,N-Dimethylacrylamide (DMAA), acrylamide (AM), and methyl acrylate (MA); and performed a single-factor experiment on the proportion of monomer, reaction temperature, initiator dosage, and developed fluid loss additive, which has a high salt tolerance and temperature tolerance. This fluid loss additive can resist salt until saturation, and it can control fluid loss in 24 mL·(30 min)⁻¹ when its dosage is 2%. The fluid loss additive can achieve the effect of fluid loss reduction by increasing the filtrate viscosity, forming a flexible elastic adsorption layer via adsorption, and blocking mud cake pores. Full article

Grouting materials with good thermal insulation and reinforcement properties are the key factors in solving the temperature control problems of high geothermal tunnels using curtain grouting, as the existing grouting materials are unable to take into account the working performance and thermal insulation properties of high-temperature environments. In view of the above problems, this paper configures a high geothermal tunnel red-mud-based grouting material (RMGS) using red mud, carries out tests on the working performance (viscosity, setting time, and compressive strength) and thermal insulation performance (thermal conductivity and specific heat capacity) of the grouting materials at different temperatures (20, 40, 60, and 80 °C), and analyses the variation rules and micro-mechanisms of the various properties at different temperatures. The results show that the increase in temperature will accelerate the viscosity development and condensation of the grouting material and will also lead to the acceleration of the attenuation of the thermal conductivity of the three types of grouting material and the reduction in specific heat capacity. In addition, the appropriate temperature can improve the compressive strength of the material. The increase in temperature will accelerate the hydration reaction speed of the grouting material and will also lead to the development of the internal pore space of the material, which affects the macroscopic properties of the material and is the reason for the effect of the temperature on the performance of the grouting material. In terms of application, the cement slurry is suitable for grouting in a static water environment, the cement–water glass bi-liquid slurry is suitable for grouting in a dynamic water environment, and the RMGS is suitable for grouting in a high-ground-temperature environment. Full article

Sodium-based bentonite is used for drilling operations because of its high swelling capacity. This type of bentonite clay is not sourced locally in many oil- and gas-producing nations. However, low-swelling clays (calcium- and potassium-based) are in abundant quantities in most of these countries. Hence, there is a need to convert low-swelling bentonite clays to sodium-based bentonite. The method used to convert low-swelling clays is more applicable to calcium-based bentonite. This research investigated a thermochemical treatment method that converted potassium-based bentonite to sodium-based bentonite. The raw clay materials were sourced from Pindinga (P) and Ubakala (U) clay deposits in Nigeria. An X-ray diffractometer (XRD), an energy dispersive X-ray (EDX), and a scanning electron microscope (SEM) were used to characterize the raw clay samples. Mud slurry was prepared by mixing 22 g of the local raw clays, 3 wt.% soda ash, and MgO at concentrations between 1 and 3 wt.% and heating at 90 °C. The result showed that the viscosities of samples P and U increased from 6 to 26 and 8 to 35.5 cP before and after thermochemical treatment, respectively. Also, due to the thermochemical treatment, the samples’ yield point, consistency factor, consistency index, and thixotropy behavior were all significantly improved. Full article

The application of polymer flocculants plays a pivotal role in the slurry separation process of shields, and the dispersant used for treating cutter mud cakes can significantly impact the effectiveness of polymer flocculants, potentially leading to reduced efficiency in slurry separation. Experiments were conducted to select appropriate flocculants and investigate the influence of dispersants on flocculant effectiveness, aiming to assess the effect of flocculants and explore the relationships and mechanisms governing their influence. Changes in the patterns of slurry flocculation were revealed in terms of flocculation-driven precipitation and vacuum-filtration effects. The purpose of this article is to provide a reference for the field application of polymer flocculants in the shield field. The conclusions are as follows. Inorganic flocculants containing 0.5% polyaluminum chloride (PAC) exhibit the most effective flocculation, demonstrating strong charge neutralization action. Organic flocculants containing 0.1% cationic polyacrylamides (CPAM) exhibit the most effective flocculation, demonstrating strong bridging and net capture effects. The dispersant sodium hexametaphosphate (SHMP) can significantly weaken the charge-neutralizing action of flocculants and slightly enhance bridging and net capture effects. SHMP can impede the flocculation of slurry with PAC. For CPAM, SHMP can enhance the flocculation of slurry at a low mass fraction (0.1% and 0.3%), while SHMP can significantly hinder flocculation at a high mass fraction (0.5% and 1%). A low mass fraction of SHMP reduced slurry viscosity to 246.3 mPa.s and enhanced vacuum filtration, while a high mass fraction of SHMP increased slurry viscosity to 667.2 mPa.s and hindered vacuum filtration. In conclusion, while dispersants reduce the effectiveness of inorganic flocculants at any mass fraction, a small number of dispersants enhances the performance of organic flocculants; thus, the organic flocculant CPAM is recommended for slurry separation. Full article