In geotechnical practice, it is often necessary to improve the properties of soil and rock in which different structures are built. For this purpose, spherical cavity blasting can be applied to expand the borehole. Such expansion may incorporate various constructive elements such as anchors and thus stabilize the slope. The paper presents the method for determining the increased volume, expansion, and deepening of the borehole as a result of spherical cavity blasting. In addition, mathematical models describing the dependency of the borehole expansion on the amount of explosive charge are presented. The models are mutually compared with the Akaike information criterion.
Monitoring and detection of seawater intrusion in coastal aquifers in Croatia are one of the water management measures that attempt to notice an increase in salinity in time. Bokanjac-Poličnik is the coastal aquifer in Croatia that is at the risk of seawater intrusion. In that area, analysis of hydro-chemical indicators will be conducted due to the occasional seawater intrusion that occurs on wells that are included in the water supply system for the City of Zadar and surrounding villages. Due to the increased exploitation during the tourism season in summer and climate changes, salinization process is more intense. The presented results indicate that two of four wells on the case study area are under the influence of salt marine water.
Excavation of clay soil is one of the most important economic branches in the northern part of Croatia. The impact of clay soil in Croatia compared to the global exploitation fields of clay soil is negligible. Modern methods of clay excavation during winter months due to negligible amounts are not profitable. Therefore, it is important to optimize clay soil excavation throughout the year to increase the efficiency of exploitation and increase profits. In the case of large amounts of precipitation (rain), clay absorbs water and becomes grain. For this reason, access to the exploitation field and excavation itself becomes impossible. Air temperature also plays an important role in excavation. Long-lasting low air temperatures below 0 °C during the winter months result in clay frost. As a result, excavation cannot occur at that time. The paper describes a new method of modeling the precipitation and air temperature on the exploitation fields of clay in Northwest Croatia on the exploitation fields of Cukavec and Cukavec II. The method involves the calculation of the drought index and use of the rescaled adjusted partial sums (RAPS) statistical method and its application on a time series of total daily precipitation and average daily temperatures as a climatic indicator of any observed area. Using this process, it is possible to determine the time period of the year when clay soil can be excavated.
This paper analyses the results of trial, construction and quarry blasting, carried out in sediment rock deposits, mainly limestone and dolomite, at diff erent locations in the Republic of Croatia. The division of the three test groups was based on the lithology changes and GSI values of the rock units at these locations. The peak particle velocity measurements with 246 recorded events, was conducted during a long period of six years. Based on the results of seismic measurements, the empirical relationships between peak particle velocity and scaled distance were established for each group. In order to establish a useful relationship between peak particle velocity and scaled distance, simple regression analysis was conducted with the Blastware software program from Instantel. The results of this study can be used to characterize ground vibration levels to the environment, through the geological strength index (GSI).
Spherical cavities made by explosive charge activation in a clay soils differ in size and shape. The mass of explosive charge lowered on the bottom of the borehole in a one-time blasting is typically relatively small and is calculated by a desired and planned performace. The effect of smaller explosive charge for spherical cavities is in principle different than continuously filled borehole in mining and blasting operations. Detonation of smaller explosive charge crushes the material in proximity of activated explosive charge. With the increase of distance from the explosive charge, the released energy in not enough for crushing of the materials, but instead compacts it. This paper is an extension of the previous research, which resulted in a smallest error of estimated in a model shown as the sum of square residuals (SS), largest value of determination coefficient (R2) and smallest loss of information through Akaike’s Information Criteria (AIC and AICc). This paper presents an extended power model of dependence of spherical cavity volume expansion on explosive charge. Extended model is a basic model with an additional parameter to ensure more precise mathematical description and further decrease of error of estimate for all efficiency indicators and for both types of explosive used.
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