MAN- MADE STRUCTURES AND GEOLOGICAL ENVIRONMENT
By S. Tabon, CE, BS, MS, MPH major in environmental health/sanitary engineering
The earth crust is made up of the solid rock. It is covered by materials most of which were derived from the rock.
There are three types of rocks namely sedimentary rock, igneous rock and metamorphic rock. Marotta and Herubin (1997) showed the cycle in which one rock type is changed to another rock type.
Rock is massive whereas soil is loose.The underlying material below the structure must be known to the engineer before any design will be made. This can be done by field and laboratory investigations in the form of soil exploration or exploratory program. Holes can be drilled into the ground and samples can be obtained for identification and for testing.
Below the civil engineering structure is either a rock or a soil other than the liquid components.
Soil is the loose material and rock is the impermeable material. The massive rock is mainly made of minerals. When the rock is weathered and the soil is produced, the resulting product may or may not retain the mineral component depending upon whether the weathering process involved only a physical disintegration of parts or a chemical reaction that when completed may result into a completely different substance or substances. Marotta and Herubin showed the rock cycle in the changing of the rock in which the weathering process results to the residual soil at time of which maybe transported and deposited as sediments of which by induration sedimentary rock can be formed. If the sediments of angular gravel with the binding material were consolidated into the sedimentary rock breccia, the angular gravel can be processed back to pieces more easily when the breccia is soft and friable. This may happen to the sedimentary rock conglomerate of which round gravel maybe obtained by processing the soft and friable rock fragments after being blasted from the source.
Sediments or aggregate materials for construction can be found in nature. They may either be gravel or sand containing silt or clay and forming part of the soil. They take several shapes being angular, rounded, elongated or flaky. They have characteristic surfaces which are either rough or smooth. Most gravel in the downstream of the river are smooth and rounded.
Rocks can be classified in accordance to their solubility in the presence of water. They can also be classed on the basis of their behaviour to change volume when exposed and unloaded. A classification on the basis of fabric, was given by Peck, Hanson and Thornburn (1974) in their book. Accordingly rocks can be classified into four categories namely, interlocking, foliated, laminated and cemented rocks. Cemented fabrics are so attached like that of the sedimentary rocks. Foliated fabrics got leaves-like compositions as in metamorphic rocks. Interlocking as in overlapping fabrics are present in most igneous rocks. Laminated fabrics are present in a number of sedimentary rocks.
Strength can be a basis of classification of rocks. Most sedimentary rocks are low in strength except a few that include dolomite. Most igneous rocks are strong except for basalt, gabbro, tuff and pumice which are low in strength. Metamorphic rocks are high in strength except soapstone, schist, serpentine, phyllite, and slate.
Most intact rocks are stronger and less compressible than concrete. They maybe rarely found. When found, routine tests and determination of bearing capacity are not necessary. If piles are driven through them, the piles might be damaged.
While it had been primarily the characteristic of soil and only secondarily the behavior of the rock which had been considered in foundation design, it is an important consideration that the features of the entire deposit of rock such as cracks be investigated. There maybe permeable portions because of the presence of joints, bedding planes, and solution cavities in massive rock. Marbles, slate and granite are not exceptions. The presence of joints, sinkholes, bedding planes, shear zones, faults, and hydrothermal alteration can dictate the adequacy of the foundation. This however is unknown unless the rock defect is exposed or its effect was known.
Allowable contact pressure by a civil work structure on rock should be based the strength of the intact rock and if defects are present, the effect of these are to be taken into consideration. For rocks without defects, the allowable contact pressure on the surface of the rock maybe taken conservatively as the unconfined compressive strength (Peck, Hanson and Thornburn, 1974). Based from the Codes of certain states in the United States, one may think that the allowable contact pressure on the massive crystalline bedrock that includes granite, diorite, gneiss, traprock, hard limestone, and dolomite were a lot higher than those of foliated rocks such as schist or slate, bedded limestone, sedimentary rocks that include hard shales and sandstones, soft or broken bedrock and soft limestone and soft shale. According to Peck, Hanson and Thornburn (1974), unless the strength of the rock deformed by one or more joints, is extremely low, the allowable contact pressure should be governed by the settlement due to the joints, and not by the strength. They presented a table of allowable contact pressure for jointed rocks on the basis of the RQD (rock quality designation). Rock qualities listed as very poor, poor, fair, good and excellent were given the corresponding RQD.
Defects by faulting can result to inclined rocks. Sloping rock surface can introduce a complication in the design and in the construction of pier foundation. Piles driven might slide along the surface.
Joint defects in rocks are of different types. They can be vertical or horizontal. More or less vertical joints can be one to several inches wide. They can be so wide that they might constitute large fraction of the base of a pier. They maybe filled or open. Intersecting joints may have larger spaces, wider at the top. Nearly horizontal joints are found in many rock masses. If close to the surface, they are likely to be open. When found underneath, they maybe filled and not open.
Most rock joints can be treated or repaired. The treatment of faults and shear zones through rock can be assessed. The treatment of open structures or solution features in rocks had been made possible.
There is the need to choose the type of soil or rock below a civil work structure to be built on land or submerged partly underwater.
There are important physical features and processes in the coastal environment which are to be understood before any design and construction of the marine structure like ports be commenced. Water wave mechanics and coastal processes are factors that are to be taken in to consideration in the coastal and port engineering design. Wind, current, waves and ice are earth features which are sources of effects or problems on the structures constructed in the sea, lagoon, estuary or inland waterways. Marine environmental problems for instance arise when there is the presence of soft bottom sediments in the basin of the harbour. In certain places, very cold ice-infested waters at harbor entrance can be hazardous to ships. Where steel has been used in the structures in the harbor, steel corrosion due to persistently hot, humid climate. Cross currents and waves can interfere with the maneuvering of a ship when it passes in and out of the interior basin of the harbour. The effect of high winds, heavy waves, and strong current in barely protected docking area can cause damage to vessels and pier installations. Insufficient protection against currents and waves can cause interruption in the loading and unloading of vessels. Excessive movement of the vessel at berth might bring about inconvenience or breakage of moorings. These can cause port operations, delays, and corresponding economic losses.
References
Marotta, T., and Herubin, C. (1997). Basic Construction Materials (5th ed).
New Jersey: Prentice Hall.
Peck, R., Hanson, W., and Thornburn, T. (1974). Foundation Engineering.
Canada: John Wiley & Sons, Inc.
By S. Tabon, CE, BS, MS, MPH major in environmental health/sanitary engineering
The earth crust is made up of the solid rock. It is covered by materials most of which were derived from the rock.
There are three types of rocks namely sedimentary rock, igneous rock and metamorphic rock. Marotta and Herubin (1997) showed the cycle in which one rock type is changed to another rock type.
Rock is massive whereas soil is loose.The underlying material below the structure must be known to the engineer before any design will be made. This can be done by field and laboratory investigations in the form of soil exploration or exploratory program. Holes can be drilled into the ground and samples can be obtained for identification and for testing.
Below the civil engineering structure is either a rock or a soil other than the liquid components.
Soil is the loose material and rock is the impermeable material. The massive rock is mainly made of minerals. When the rock is weathered and the soil is produced, the resulting product may or may not retain the mineral component depending upon whether the weathering process involved only a physical disintegration of parts or a chemical reaction that when completed may result into a completely different substance or substances. Marotta and Herubin showed the rock cycle in the changing of the rock in which the weathering process results to the residual soil at time of which maybe transported and deposited as sediments of which by induration sedimentary rock can be formed. If the sediments of angular gravel with the binding material were consolidated into the sedimentary rock breccia, the angular gravel can be processed back to pieces more easily when the breccia is soft and friable. This may happen to the sedimentary rock conglomerate of which round gravel maybe obtained by processing the soft and friable rock fragments after being blasted from the source.
Sediments or aggregate materials for construction can be found in nature. They may either be gravel or sand containing silt or clay and forming part of the soil. They take several shapes being angular, rounded, elongated or flaky. They have characteristic surfaces which are either rough or smooth. Most gravel in the downstream of the river are smooth and rounded.
Rocks can be classified in accordance to their solubility in the presence of water. They can also be classed on the basis of their behaviour to change volume when exposed and unloaded. A classification on the basis of fabric, was given by Peck, Hanson and Thornburn (1974) in their book. Accordingly rocks can be classified into four categories namely, interlocking, foliated, laminated and cemented rocks. Cemented fabrics are so attached like that of the sedimentary rocks. Foliated fabrics got leaves-like compositions as in metamorphic rocks. Interlocking as in overlapping fabrics are present in most igneous rocks. Laminated fabrics are present in a number of sedimentary rocks.
Strength can be a basis of classification of rocks. Most sedimentary rocks are low in strength except a few that include dolomite. Most igneous rocks are strong except for basalt, gabbro, tuff and pumice which are low in strength. Metamorphic rocks are high in strength except soapstone, schist, serpentine, phyllite, and slate.
Most intact rocks are stronger and less compressible than concrete. They maybe rarely found. When found, routine tests and determination of bearing capacity are not necessary. If piles are driven through them, the piles might be damaged.
While it had been primarily the characteristic of soil and only secondarily the behavior of the rock which had been considered in foundation design, it is an important consideration that the features of the entire deposit of rock such as cracks be investigated. There maybe permeable portions because of the presence of joints, bedding planes, and solution cavities in massive rock. Marbles, slate and granite are not exceptions. The presence of joints, sinkholes, bedding planes, shear zones, faults, and hydrothermal alteration can dictate the adequacy of the foundation. This however is unknown unless the rock defect is exposed or its effect was known.
Allowable contact pressure by a civil work structure on rock should be based the strength of the intact rock and if defects are present, the effect of these are to be taken into consideration. For rocks without defects, the allowable contact pressure on the surface of the rock maybe taken conservatively as the unconfined compressive strength (Peck, Hanson and Thornburn, 1974). Based from the Codes of certain states in the United States, one may think that the allowable contact pressure on the massive crystalline bedrock that includes granite, diorite, gneiss, traprock, hard limestone, and dolomite were a lot higher than those of foliated rocks such as schist or slate, bedded limestone, sedimentary rocks that include hard shales and sandstones, soft or broken bedrock and soft limestone and soft shale. According to Peck, Hanson and Thornburn (1974), unless the strength of the rock deformed by one or more joints, is extremely low, the allowable contact pressure should be governed by the settlement due to the joints, and not by the strength. They presented a table of allowable contact pressure for jointed rocks on the basis of the RQD (rock quality designation). Rock qualities listed as very poor, poor, fair, good and excellent were given the corresponding RQD.
Defects by faulting can result to inclined rocks. Sloping rock surface can introduce a complication in the design and in the construction of pier foundation. Piles driven might slide along the surface.
Joint defects in rocks are of different types. They can be vertical or horizontal. More or less vertical joints can be one to several inches wide. They can be so wide that they might constitute large fraction of the base of a pier. They maybe filled or open. Intersecting joints may have larger spaces, wider at the top. Nearly horizontal joints are found in many rock masses. If close to the surface, they are likely to be open. When found underneath, they maybe filled and not open.
Most rock joints can be treated or repaired. The treatment of faults and shear zones through rock can be assessed. The treatment of open structures or solution features in rocks had been made possible.
There is the need to choose the type of soil or rock below a civil work structure to be built on land or submerged partly underwater.
There are important physical features and processes in the coastal environment which are to be understood before any design and construction of the marine structure like ports be commenced. Water wave mechanics and coastal processes are factors that are to be taken in to consideration in the coastal and port engineering design. Wind, current, waves and ice are earth features which are sources of effects or problems on the structures constructed in the sea, lagoon, estuary or inland waterways. Marine environmental problems for instance arise when there is the presence of soft bottom sediments in the basin of the harbour. In certain places, very cold ice-infested waters at harbor entrance can be hazardous to ships. Where steel has been used in the structures in the harbor, steel corrosion due to persistently hot, humid climate. Cross currents and waves can interfere with the maneuvering of a ship when it passes in and out of the interior basin of the harbour. The effect of high winds, heavy waves, and strong current in barely protected docking area can cause damage to vessels and pier installations. Insufficient protection against currents and waves can cause interruption in the loading and unloading of vessels. Excessive movement of the vessel at berth might bring about inconvenience or breakage of moorings. These can cause port operations, delays, and corresponding economic losses.
References
Marotta, T., and Herubin, C. (1997). Basic Construction Materials (5th ed).
New Jersey: Prentice Hall.
Peck, R., Hanson, W., and Thornburn, T. (1974). Foundation Engineering.
Canada: John Wiley & Sons, Inc.