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Exploration of Deposits and Laboratory Examinations

Dr. KRAKOW Rohstoffe GmbH offers complex services for the striking and exploration of clay raw materials.

The professional prospecting and exploration of clay deposits requires decades of experience. This concerns the choice of location as well as the type and number of bore holes in particular. Due to reconnaissance mistakes, several million investments were lost up again and again. As a result, production plants were built at the wrong place and will be a source of high costs for purchasing external raw materials

Geological drilling project/Covasna, Romania (2008)
Geological drilling project/Covasna, Romania (2008)
Air-proof packaging of cores/Covasna, Romania (2008)
Air-proof packaging of cores/Covasna, Romania (2008)
Regulatory consultation of the exploration area / Bucharest, Romania (2006)
Regulatory consultation of the exploration area / Bucharest, Romania (2006)

We offer the following services:

Preliminary Prospecting Survey

Systematic preliminary prospecting survey of resource rich greater area. Sampling operation in existing regional outcrops in the planned exploration area.

Drilling Schedule and Concept

Sinking by drilling the first holes in a widespread grid. Creation of a drilling concept with type, number, location and final depth of the exploration boreholes.

Geological Supervision

Geological supervision of the drilling as well as documentation of the cores. Individual adaption of the drilling schedule depending on initial results.

Sampling and Transportation

Qualified core sampling and transportation to our ceramic laboratory for an extensive raw material examination. In case of foreign orders, handling all formalities.

Laboratory Qualifying Examination (Suitability Tests)

The raw material investigation includes the measurement of ceramic-technological characteristic value in our ceramic laboratory. Geo-referenced documentation of the exploration results with site plan, drill logs, geological profiles and ISO plans.

Licensing Procedures

Compilation of all application documents for the approval procedure. Coordinate the scope with the responsible authority and ministry.

Preliminary Prospecting Survey and Exploration Methods

A distinction is made between the preliminary prospecting survey and direct and indirect exploration methods. The preliminary prospecting survey includes the providing, review and evaluation of all available geological data as well as the preliminary investigation of a licensability considering competing utilization.

The intention of the preliminary survey is the striking of potentially clay rich areas and the creation of a drilling schedule with type, number and drilling depth of the planned exploration points. These points are to be documented in site plans and assessed with regard to their estimated costs.

The direct exploration cover all kind of drills and test pitting by hydraulic excavator. Other methods such as seismic measurements, drill hole surveys and geophysical measurements on the terrain surface belong to the indirect exploration methods.

General Information on Drilling Methods

Drilling methods and drill diameters primarily comply with the type and quality of the required raw material samples. Generally drilling methods in which the bore hole cuttings are extracted as intact as possible are preferred. Due to the lacking erosion resistance of plastic clay as well as overlying unconsolidated rocks, dry drilling methods should be used. The boreholes are normally lined according to the drilling progress, so that no bore hole detritus gets into the cuttings.

In order to prevent settlement and environmental damage, the boreholes should be carefully filled by complete borehole linings/casings. In case of encountering confined groundwater the hydraulic barrier effects of the original interlaminar bonding have to be restored by filling up the borehole with technical swelling clay.

Combined ramming core/cable core drilling method SK6L
Combined ramming core/cable core drilling method SK6L
Clearing drill of the core pipe according to procedure SK6L
Clearing drill of the core pipe according to procedure SK6L
Extraction of the core pipe with core inside a PVC lining
Extraction of the core pipe with core inside a PVC lining

Recommendation for the Brick and Tile Industry

Out of many various drilling methods, the combined ramming core/ cable core drilling SK6L is the most advisable one. In order to obtain completely intact and depth equal raw material samples out of the geological formation of category 1 - 5 according to DIN 18 300 (clay, loam, marl and other granular soils), the ramming core sampling is successfully used.

The ramming core pipe with a drill bit, which should be adapted to the substrate, is driven into the ground with a pile hammer. After that, a casing pipe (diam. 168 mm) is drilled around the ramming core pipe, which secures the borehole wall. The core pipe is then detached from the bottom of the borehole and is pulled back by a cable catch mechanism. A drill core diameter of 101 mm has been generally accepted, because the ratio of the gotten samples to the borehole diameter is very convenient.

Schematic of a ramming core/ cable core drilling (source: Krakow & Homrighausen, 1997)
Schematic of a ramming core/ cable core drilling (source: Krakow & Homrighausen, 1997)
Cores of ramming core sampling, category 1 - 5 according to DIN 18 300
Cores of ramming core sampling, category 1 - 5 according to DIN 18 300
Cores of cable core drilling, categories 1 - 5 according to DIN 18 300
Cores of cable core drilling, categories 1 - 5 according to DIN 18 300

For the exact exploration of geological formations of category 6 - 7 according to DIN 18 300 (claystones, shales, phyllite and other solid rocks) the rotary cable core drilling with double core tube is the preferred exploration method. The prevalent drilling diameter is 146 mm with a resulting core diameter of 101 mm. The drilling fluid is pumped with piston pumps out of a flushing tank or flushing pool and runs through the drill rods between the outer and inner pipe (casing and core pipe). This technique largely avoids the core of being negatively affected by the drilling fluid.

Successful exploration of clay deposit for brick production/Egge Mountains (2007)
Successful exploration of clay deposit for brick production/Egge Mountains (2007)
Brick clay terrain yet unaffected by surface mining of Rhaetian age/Egge mountains (2007)
Brick clay terrain yet unaffected by surface mining of Rhaetian age/Egge mountains (2007)
Disclosed brick clay terrain of Rhaetian age/Egge mountains (2016)
Disclosed brick clay terrain of Rhaetian age/Egge mountains (2016)

The core quality and core extraction decisively depend on the choice of used drill bits. The core extraction has to be at 95 %. For solid clays, hard nail bits or corborite-coated bits are generally recommended. Using the cable core drilling method, it is possible to drill uncased core drillings (with exception of the standard pipe) of several 100 meters. This makes it an economical drilling method to obtain a 'clean' exploration with intact and depth equal core samples out of solid rock formations.

Test pitting with hydraulic excavator

With a hydraulic backhoe, geological formations of category 1 - 5 according to DIN 18 300 can be easily explored up to depths of about 5 meters beneath the surface. Especially the large-scale trial pit proportions, like the extraction of large sample quantities with low expenditure of time and costs, make this an advantageous method. In a short time many outcrops can be excavated and geologically investigated.

Negative points of this method are the low depth of exploration and the extent of field damages. Afterwards, the outcrops have to be closed thoroughly and surface compatibly. Above all, it is recommended to excavate trial pits during the exploration to narrow down the exploration grid and obtain sufficient sample quantities. 

Trial pit as a direct exploration method in unconsolidated rocks
Trial pit as a direct exploration method in unconsolidated rocks
Possibility to obtain large sample quantities of unconsolidated rocks
Possibility to obtain large sample quantities of unconsolidated rocks
Possibility to realize initial production trials in the brickworks
Possibility to realize initial production trials in the brickworks

Geophysical Measurements

Geophysical measurements on the terrain surface are methodically based on the tracing of boundary surfaces between layers of different physical properties, such as the propagation velocity of seismic waves or the electrical resistance. The prerequisite is that the substrate is preferably only two-layered and that these layers differ as clearly as possible from each other in the above mentioned properties.

Advantages of this method are the comprehensive exploration and the comparatively low expense. The limitations result from the required correlation between the obtained geophysical data and the measurements of the direct exploration, generally of core drillings. In case of positive indication of direct exploration methods, geophysical exploration can recommended to narrow down the exploration grid.

Documentation and Prearrangement of Excavation Procedure

Arrangements for the deposit exploration are generally associated with a high expense and risk. Therefore, all results should be accurately documented. For this purpose, all exploration points and sampling locations have to be geo-referenced and documented in appropriate maps. To provide proof of the deposit, which is required from the authorities, visual field results/bore logs have to be confirmed by qualified laboratory tests. It has to be proven that the explored deposit has a sufficient dimension.

In line with a separate ceramic-technological test, it has to be shown that the explored deposit is actually suitable for the intended purpose. In reference to the brick and tile industry, it is necessary to roughly differentiate between the main product groups of bricks, clinker bricks and roof tiles. The period of excavation procedure vary from one country to another. The procedures become more and more complicated over time. In the EU, periods of five to ten years are realistic. These lead times are underestimated over and over again. Often with fatal consequences.