VNUHCM Journal of Earth Science and Environment

Numerical modelling technique for rock mass in underground coal mine by using grain-based model

Dung Tien Le — 2023-03-08

The stability of rock mass around longwall or excavation in underground coal mine is a prerequisite for the safe and continuous coal production. In practice, instability incidents commonly occur at longwall face or longwall roof that causes serious occupational injury or even death. Current research on the instability has not sufficiently interpreted the formation and propagation of rock mass failure, mostly due to the discontinuous, anisotropic, inhomogeneous and non-elastic nature of rock mass. To assist interpretation of the above stability behaviour, this paper presents a study to improve the numerical modelling technique of rock mass around longwall by using Grain-Based Model. The modelling technique uses Discrete Element Methods and the grain structure Voronoi. A procedure for calibrating rock properties in modelling technique is proposed and validated through application for field rock mass at Ha Lam coal mine, Quang Ninh province, Vietnam. The paper also presents a technique for selecting grain size and monitoring the modelling efficiently. The proposed procedure along with the modelling code are useful for investigation of rock mass around underground excavations from which technical solutions for safe and continuous production can be established.

Evaluation and ranking of several enterprises according to the Binh Duong green Book criteria in 2022

Huyen Thi Thu Do — 2023-05-09

Since 2010, the authorities of Binh Duong province has focused on encouraging and prompting establishments that perform well in environmental protection through the form of Binh Duong Provincial Green Book every two years. This is for the purpose of honoring the establishments operating in Binh Duong province that good at environmental protection, creating the motivation to improve environmental management and more businesses will be encouraged in doing well in environmental protection; thereby bringing positive results in the province's environmental protection work. In 2022, to follow up the innovations in environmental protection regulations and to contribute to the implementation of the state's policy on environmental protection as prescribed in Clause 8 Article 5 of the Law on Environmental Protection in 2020, the process and set of criteria for assessing in Binh Duong provincial Green Book have been adjusted in accordance with the provisions of the Law on Environmental Protection 2020, Decree 08/2022/ND-CP and Circular 02/2022/TT-BTNMT. The results applied in 95 enterprises in many different industries and areas in Binh Duong province showed that 53.25% of enterprises met the criteria of the Green Book. The set of evaluation criteria has a total score of 108 points, including 03 groups of main criteria and sub-criteria focusing on assessing compliance with environmental regulations and standards and industrial hygiene; compliance assessment of environmental procedures, records and related matters; and incentive scoring criteria. Each criterion group is scored based on its importance. Based on the actual survey results, the ranking of each enterprise is based on the score calculated according to this set of criteria. Up to 46.75% of enterprises did not meet the criteria due to many objective and subjective reasons, some of which are mainly as follows: Lack of certification of completion of environmental protection works or the waste treatment systems as prescribed in Decree 40/2019/ND-CP; the non-standard/normative of the results of environmental analysis at the time of survey; operating not in accordance with the approved Environmental Impact Assessment (EIA); and lack of approved environmental records. This assessment result has been used as a basis by the People's Committee of Binh Duong province to commend and reward enterprises with good achievements in environmental protection work in the province.

Research on the exchange between groundwater of Cu Chi district, HCM City and Sai Gon river water by isotope techniques

Nguyen Si Quang — 2023-05-14

In the earth's water cycle, groundwater is the most difficult component to assess. Scientists have long used isotopes to find out whether groundwater is replenished, and where it comes from. Water from different locations has different isotopic characteristics and is known as a "fingerprint". Scientists use these fingerprints to track the movement of water along its path throughout the entire water cycle. The isotope ratios 2H/1H and 18O/16O in water provide a wealth of information about the separation of water molecules in the hydrosphere cycle. The relationship between the isotope ratios of water in an area characterized by the local meteorological waterline, known as a reliable reference value for studies to determine the origin of groundwater recharge. soil. The research paper uses 2H and 18O isotopic data monthly monitored at 03 wells of households, 01 independent monitoring well in the Pleistocene aquifer along the Saigon River, and water data of the Saigon River. The initial research results show that the Pleistocene aquifer in Cu Chi district and the surface water of the Saigon river had an exchange at the end of the dry season - the beginning of the rainy season, from February to May 2019 respectively, and there was a direct replenishment of the surface water. from rainwater.

Land use influencing the pesticides concentration in Ma river and its tributaries in Thanh Hoa province

Hien Trong Dieu Le — 2023-05-14

Surface water frequently contains pesticide residues, which could be a hazard to freshwater ecosystems and biodiversity. Pesticides can enter waters through a number of different pathways, but oncentrations is runoff from irrigation or precipitation. This study presents an investigation of banned pesticides used across the range of land use in catchments of the Ma river and its tributaries in Thanh Hoa province, Vietnam in period of time 2011-2015. Applying principal component analysis (PCA), we investigated the relationship between specific pesticides and land use. Besides, the method of aggregating monitoring locations known as cluster analysis (CA) has also been applied in this study. All ten banned pesticides including eight insecticides (aldrin/dierin, BHC, chlordane, endrin, heptachlor, lindan, malathion, and parathion) and two herbicides (2,4D and paraquat) studied still occur in surface water due to their persistence and remobilization during floods, runoff and not presumably influenced by the fraction of land uses area in the catchments. Clustering results revealed banned pesticides still occurs in some areas.

Solutions for sustainable livelihood development for fishers in the buffer zone of Hon Cau Marine Protected Area, Binh Thuan province

Quoc Phu Dao — 2023-05-14

Choosing a sustainable livelihood model for residents in the buffer zones of protected areas is a central task and the key to the success or failure of protected areas. This study investigates and assesses resource and livelihood issues of people in Hon Cau Marine Protected Area, Binh Thuan province. In addition, the study also surveys, collects information and evaluates the competitiveness in the aspect of marine ecotourism of the study site and tourist attractions of the same type. The survey results show that there are two economic directions that can be developed to support the livelihoods of people in the buffer zone: tourism and aquaculture. In particular, when analyzing and evaluating the competitive advantages of local fishermen in the field of tourism and aquaculture, the results of the SWOT analysis show that aquaculture is a favorable and suitable direction for the economy, qualifications and experience of fishermen to replace inshore fishing livelihoods. The area's marine ecotourism has low competitiveness and low job-creation capacity. Therefore, the research team proposes that localities should prioritize investment in technology and financial transfer for people in the buffer zone in the field of high-tech aquaculture to transform livelihood models for affected people, directly from the protected area's fishing ban.