HW3 -3

pdf

School

Tarrant County College, Fort Worth *

*We aren’t endorsed by this school

Course

2367

Subject

Geography

Date

Oct 30, 2023

Type

pdf

Pages

Uploaded by LieutenantTrout3697

CONSTRUCTION MATERIALS AND METHODS Subject: Homework #3 49 Points 1. What size of soil particles are considered as fine soil? What are these types of soil considered unstable for construction? (6 points) Due to a number of its intrinsic characteristics, fine soils — which include particles between 0.002 mm and 0.075 mm in size — are regarded as unstable for use in building. Since clay and silt make up most fine soils, they have a high degree of plasticity, which makes them susceptible to volume and form changes in reaction to variations in moisture content. Because of this quality, structures and their foundations may have significant settlement problems and structural instability. Additionally, fine soils have low permeability, which hinders water drainage and could lead to erosion, swell, and other water-related issues. Their propensity to expand when wet and contract when dry can cause disruptive cycles of soil movement that harm structures and foundations. Additionally, compared to coarser soils like sand and gravel, fine soils often have lower bearing capacities, making them less able to carry heavy loads without experiencing severe settlement or deformation. To address these issues, soil stabilization measures must be used, such as careful site preparation, compaction, moisture control, and the application of suitable foundation designs and materials. For assessing the feasibility of fine soils for construction projects and for developing customized foundation solutions that can efficiently distribute loads and lower the risk of settlement and structural damage, precise soil testing and analysis are crucial. 2. Which building would experience vibrations with higher intensity during an earthquake; Building located on a rock or building located on soft soil? (2 points) Why? (3 points) Compared to structures placed on rock or harder ground, buildings positioned on soft soil are more prone to intense shaking during an earthquake. This disparity results from the divergent seismic wave transmission and amplification properties in various soil types. One of the main types of seismic waves produced during an earthquake is the shear wave (S-wave), which has a particularly low velocity in soft soils like clay or loose sediment. Due to the low stiffness and compressibility of soft soil, seismic waves tend to slow down and may experience significant amplification when passing through it. Due to the increased ground motion and surface shaking caused by this amplification effect, buildings located on soft soil experience higher intensity vibrations. Rock or firm ground, on the other hand, permits seismic waves to keep their velocity and incur minimal amplification due to its significantly higher S-wave velocity, resulting in lower ground motion and shorter-duration shaking for buildings built on such stable terrain. While technical modifications might increase a structure's resilience to earthquakes, the intrinsic characteristics of the soil continue to play a critical role in determining the strength of vibrations felt during seismic events.

CONSTRUCTION MATERIALS AND METHODS Subject: Homework #3 49 Points 3. Define soil liquefaction. (4 points) Which type of soil is more prone to liquefaction? (3 points) A geological phenomenon known as soil liquefaction occurs when soil briefly loses its strength and takes on the characteristics of a liquid. It is most frequently seen during earthquakes. Due to the cyclic loading of seismic waves, extra pore water pressure builds up inside the soil pores, resulting in this transition. Basically, the soil loses its capacity to support weights and transitions to a liquid-like state, which frequently has catastrophic repercussions for any structures erected on or inside the liquefied soil. More liquefaction-prone soils are often loose, saturated, and made up of tiny, non-cohesive particles. These comprise silty soils, which lack cohesive strength and easily allow water to flow, and sandy soils, ranging from fine to coarse sands. Due to the extensive pore spaces in loose, inadequately compacted soils, which can collect water and build pressure during seismic shaking, these soils are also susceptible. The formation of excess pore water pressure, which causes liquefaction, is significantly influenced by the presence of water, whether from saturation or a high groundwater table. Particularly vulnerable are young, unconsolidated sediments, which are frequently found in river deltas and coastal areas. In contrast, cohesive soils with superior internal structure and cohesion, such as clays and well- compacted soils, are less prone to liquefaction because they can withstand strength loss and deformation due to seismic activity. When constructing structures in earthquake-prone regions, engineers take soil liquefaction potential into account. To reduce the danger of damage from liquefaction-induced soil behavior, engineers use a variety of measures, such as ground improvement and deep foundations. 4. Provide two alternative solutions when the bearing capacity of the soil is not enough to sustain the loads of the structure. (3 points) Which one would you prefer and why? (3 points) Engineers often look at two potential solutions when faced with the problem of insufficient soil carrying capacity to support a structure's loads: soil improvement and deep foundations. The main goal of soil improvement techniques is to increase the current soil's ability to support loads on the construction site. Compaction, grouting, and vibrocompaction are a few of these techniques. Compaction improves soil's load-bearing ability by decreasing empty areas and increasing soil density. In order to increase cohesiveness and strength, grouting is injecting a cementitious or chemical grout into the soil. This method is particularly helpful for loose or sandy soils. To efficiently densify granular soils, vibratory probes are used in vibrocompaction. When dealing with relatively superficial layers of poor-quality soil, soil repair is frequently used because it is more affordable for smaller structures. However, the type of soil and the level of improvement needed will affect how effective it is. On the other hand, when unfavorable soil conditions are present at significant depths, deep foundations, such as piles or caissons, are used. Long columns, or piles, are driven deeply into the earth to shift loads to bedrock or layers of soil that are more capable of supporting the loads. Caissons are concrete-filled, large- diameter drilled shafts that reach deeper levels of bedrock or firmer soil to provide a secure foundation. For difficult settings, deep foundations are frequently chosen to ensure the stability and long-term performance of the structure. The preferred option among these choices depends on a number of variables, such as the project's characteristics, budgetary concerns, and

CONSTRUCTION MATERIALS AND METHODS Subject: Homework #3 49 Points construction limitations. The most appropriate and cost-effective option for a given project must be determined after a thorough geotechnical analysis and engineering judgment, with deep foundations being preferred when dealing with severe soil constraints and depths. 5. Which system is used to dewater the soil if the water table is high and there is no existing building near the construction site? (3 points) A. Sumps B. Well points Well points are frequently utilized to dewater the soil when the water table is high and there are no nearby existing structures. A sort of groundwater control technique called as "well points" entails the insertion into the earth of numerous, closely spaced, small- diameter wells. These well points often include a vacuum or suction pump and are attached to a common header pipe. Water is drawn into the well points from the surrounding earth by the pump-created vacuum in the header pipe. Through this method, the groundwater table close to the construction site is effectively lowered, enabling excavation and construction to proceed in a generally dry environment. Sumps, on the other hand, are typically used to collect and remove groundwater in combination with the foundation of an existing building. They are not frequently used as the main technique of dewatering a development site when there is a high-water table, and no surrounding structures exist. 6. Define differential settlement. What type of the following foundation system is prone to differential settlement? (4 points) Differential settling describes the uneven or uneven movement of distinct foundational components of a structure. It happens when one element of a structure settles more than another, causing uneven vertical displacement of the foundation's various sections. Shallow foundations are one type of foundation system that is particularly vulnerable to differential settlement, especially when built on uneven or compressible soils. Spread footings and slab-on- grade foundations are examples of shallow foundations that rely on the supporting capability of the soil immediately beneath them. Differential settlement may result from varied soil qualities present in different parts of the foundation area. In contrast, the possibility of severe differential settlement is decreased by deep foundations such as piles or caissons that extend into deeper, more solid soil or bedrock strata. Deep foundations mitigate the impacts of uneven soil conditions close to the surface by transferring the loads of a structure to a more constant and stable stratum. To ensure the stability and lifetime of a structure, engineers carefully evaluate the soil conditions and consider the possibility of differential settlement while designing foundations. 7. Name two alternatives to a combined footing (4 points) Isolated footings and mat foundations (sometimes called raft foundations) are two alternatives to combined footings, a type of foundation used to support many columns or load-bearing

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

CONSTRUCTION MATERIALS AND METHODS Subject: Homework #3 49 Points elements of a structure. When each column or load-bearing member needs its own distinct footing, isolated footings, also known as individual footings or spread footings, are used. These footings are specifically made to transfer the weight of each individual column to the bedrock or soil below. When columns are distant from one another and a continuous footing is not required to span numerous columns, isolated footings are frequently employed. Contrarily, mat foundations are broad, continuous concrete slabs that cover the whole footprint of a building. They are preferred when the loads imposed by the columns or walls are significant or the soil conditions are difficult. They are also referred to as raft foundations. In situations where individual or combination footings may not be viable because of severe loads or poor soil conditions, mat foundations help to distribute the structure's weight uniformly over a large area, lowering the possibility of differential settlement and providing stability. The decision between these options is influenced by several variables, such as the structural load distribution, the properties of the bedrock or soil beneath, and the placement of the building's columns or other load-bearing parts. 8. Define frost depth. (3 points) Frost depth is the deepest point at which the earth in a specific area freezes in the winter or during cold spells. It is the depth at which groundwater and soil combine to freeze and form ice. The local climate, geographic location, and average winter temperatures all have a significant role in determining how deep the frost line is. Understanding the frost depth is essential in the construction industry since it can significantly affect the design and stability of structures, particularly foundations. For instance, to prevent frost heave, which happens when frozen ground expands and lifts foundations, potentially causing structural damage, building foundations must be built below the frost depth. While foundations can be built closer to the surface in places with shallow frost depths, they must be buried further underground in areas with deep frost depths to prevent frost-related problems. Therefore, for good construction planning and design in cold regions, understanding the local frost depth is crucial. 9. Why can’t we build slab on -ground foundation in an area with cold climate? (3 points) We cannot construct a slab on ground foundation in a cold climate because the ground freezes in a cold climate, which can move to the worst portion of the slab and ultimately result in cold floors in the winter as well as concrete floor shrinking. 10. Why can’t we build slab on -ground foundation in an area with cold climate? (2 points) Due to the following factors, we are unable to construct a slab on ground foundation in that area. Concrete slabs come in a variety of sizes. Therefore, if the soil is clay-rich, the concrete slab may shift or sink over time because of the clay compressing under the weight of the concrete. Additionally, it can remove moisture from the concrete itself, leading to uneven curing and brittle bases. The slab will move, and the clay will expand; this could lead to cracking and have an impact on the walls, doors, and windows. Uneven soil settlement will alter the loading on the slab and result in a rapid collapse of the building.

CONSTRUCTION MATERIALS AND METHODS Subject: Homework #3 49 Points 11. (A) List one type of foundation that could be constructed for a low-rise building on stable soil (2 points), and (B) one type of foundation that could be constructed on expansive soil (2 points). A shallow foundation is one style that could be built for a low-rise building on stable soil. This kind of foundation often comprises of a concrete footing or slab that distributes the building's weight over a broader area, ensuring stability and reducing settling. A deep foundation is one form of foundation that could be built on vast terrain. This kind of foundation penetrates the ground more deeply, avoiding the topsoil layer and reaching a layer of soil that is more stable. Drilled piers or driven piles are examples of deep foundations. This aids in avoiding foundation movement and damage brought on by soil movement brought on by variations in moisture levels. Additionally, in expansive soil conditions, a properly designed and built moisture barrier may be employed to restrict soil moisture infiltration and movement. Bonus Questions: 12. Which foundation can be used for a building located on the expansive soil (Clay)? (Select all apply). (4 points) A. Mat foundation B. Raft foundation C. Steel pile D. Footings E. Reinforced concrete pier 13. Which one of the following foundations can’t be constructed on expansive soil? (1 point) Why? (3 points) A. Wall and column footings and ground floor comprising a reinforced concrete slab B. Grade beams and drilled piers with (elevated) ground floor over a crawl space This foundation can't be constructed on expansive soil because of Expansive Soil Movement: Expansive soils expand and contract significantly as a result of variations in moisture content. When solid constructions like concrete slabs are subjected to this movement, the pressure can be so great that fissures and structural damage might result. Lack of Flexibility: Concrete slab footings for walls and columns only offer a small amount of flexibility to allow soil movement. The foundations of expansive soils must be able to adjust to these changes.

CONSTRUCTION MATERIALS AND METHODS Subject: Homework #3 49 Points 14. Specify the different components of the foundation and slab in the following figure. (2.5 points) 1. It is the concrete work, which includes the foundation slab and foundation column. 2. Top most layer of the concrete is the foundation slab , but the indicated point shows the reinforcement of the slab 3. This diagram illustrates the bottom deck of the foundation, which is created in the shape of a truss and serves as a continuous support for the slab load above. Gravels are typically placed here to act as a moisture barrier for the upper slab. 4. The joint between the foundation and the footing the top pillar is called as foundation or some times as stem wall and the bottom is called as footing 5. It is the main footing of the structure (Answers are from left to right)

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version