The effect of water content on the strength of rock

Introduction
In order to design all type of buildings, it is necessary to understand the ground condition i.e. soils and rocks which the building foundations are based on. The occurrence of buildings failure, therefore, can lead directly to the problem of underground conditions i.e. bedrock which support the whole building to standing. In addition, rock is one mainly of an aggregate in the cement production to build the building that means the strength of rock can affect directly to the building. The need to understand rocks type and their properties are significantly for the designers to design buildings and this enables designers to effectively design.
Rocks are comprised of many aggregate of mineral particles which is occurring in natural and bonded together with granular structure and texture. Rock in the geology can separate by the classification of grain size, genetic structure, hardness and quartz. but there are still have their individual characteristic and properties. The geologist separate rock in 3 types: igneous rocks, sedimentary rocks and metamorphic rocks.

Pore spaces or voids in rock are the most important that will effect of rock strength and rock properties, namely, the mechanical properties of rock derived from the physical characteristic of rock. Type and structure of rock are related to the amount of porosity and the method of formation of rock can relate to the degree of porosity. For instance, igneous rocks which magma is slowly cooling have no porosity or the least porosity of 3 types of rock, on the other hand, the rock with rapidly cooling then it will have more porosity than those slowly cooling lava but it not in the case of sedimentary rocks which the porosity depending on the sizing, grading and precipitation of materials. If the rock have many porosity or voids, the strength lead to reduction result of the loss of internal cohesion i.e. molecular and mechanical and that can lead water seep through inside, absorb and keep in the pore spaces these are the most effective for the strength of rock.
Many research are trying to understand the water content affect on rock strength but the results seem to be different on each other which depending on the type of rock and its source that means if the specimen come from difference areas then the results to show the strength of rocks will be different too, even if, the same type of rock.
In this research will comparing the strength between an unlikely of the two sedimentary rocks: limestone and chalk rock which both consist of the mineral calcite which is calcium carbonate or CaCO3 is most commonly marine organisms and used for Portland cements, mortars and concretes. Limestone is usually an organic sedimentary rock and made up mostly of calcium carbonate but some limestone have a high proportion of magnesium carbonate, whereas, chalk rock is a type of soft limestone, porous and made up almost 99.9% of pure calcium carbonate. The quantity of calcium carbonate should effect on the strength of rock that the result will show by using an unconfined compressive strength test in saturated conditions. In general, sedimentary rocks are weak in compressive strength which relates to amount of the pores space in rock, thereby, the sample of both specific rocks should be naturally lower in compressive strength and sensitively to the degree of moisture content. Namely, when the water content increases then the compressive strength is decreased.
Statement of the Problem