## 7 Conclusions, Reservations and Prospects for Further Developments  
There are contradictory attitudes to this problem in the academic world and in the real world of contractors. Academics tend to provide very \"in depth\" (profound) analysis of the problem, analyzing and preferably testing all possible combinations of parameters under study. Practitioners, especially in the geotechnical engineering world, where the range of uncertainty is much higher than in other sectors of the construction industry, prefer to develop a methodology that makes it possible to standardize the design and execution  
Figure 12: Absolute displacement map, SF = 1.91.  
phases of the project. And, keeping that practice in mind, understanding the diversity of pollution along this particular site, we decided to use the simplest cement stabilization and check the resulting slope stability on the basis of laboratory derived composite parameters. The MES numerical calculations of the storage site stability, performed using the cohesion and angle of shearing resistance tangent reduction method, and considering the results obtained, demonstrated that the planned storage site will be stable (SF = 1.71-1.91 > 1.5). It must be underlined that the original data used for numerical studies were derived from laboratory tests and subject to critical analysis related to the fact that the samples tested in the laboratory provide upper boundary values as compared with the field results. The authors still support their statements that proper numerical modelling of geotechnical problems related to improved soils requires individual testing of the resulting composites, concerning optimal composition (binder, additives) [34] and their final mechanical properties. That last issue is usually underrated, as most of the published results refer to the standard 28-day time of curing. The authors' recent experience proves the necessity of prolonging the curing times of the DSM samples up to two or even three months to gain valuable and reliable information [35]. But this should always be tested individually and there is no real chance to obtain juxtaposed data for all possible combinations of soils and binders. Even the actual temperature may be a crucial factor concerning the final composite quality. Concerning the second case study and results given in Table 2, one may observe that application (addition) of 1.5% of active carbon (per resulting weight of sample) to cement grout was beneficial for both uniaxial compressive strength and elastic modulus. The measured values of strength and stiffness were in every case more favorable for composite with active carbon addition (within a range of 7-14%). That looks very promising concerning the practical outcomes, but due to the limited number of samples and possible various behavior of composites subjected to other contaminations, the wide application of active charcoal should be preceded by additional and numerous experiments. It must be concluded here that charcoal is not a cure for every pollution form in the ground. Recent developments concerning cement stabilization of chromium waste by solidification presented in [36] seem to be very promising. However, the authors' own similar experiment with charcoal addition concerning heavy metals did not bring any significant benefits concerning both the stiffness and strength of the resulting composite (compared to cement stabilization only). As was previously stated, an experiment in the laboratory, prior to numerical modelling and certainly before excessive earthworks, is mandatory for optimal design. Concerning the unique composition of contamination and the ground under study, there is no direct application to other cases (e.g., gas and oil cementation, buildings, etc.). But the proposed \"way of thinking\" about the problem seems to be pretty universal. No matter which geotechnical problem you want to address, please refer first to laboratory testing, which is overall cheaper than any mistake in the projects with large volume of earthworks.