Reasons for collapsing of foundation

There are several reasons for collapsing of foundation which range from poor soil condition, structural faults etc. Given below, some of the major causes for collapsing of foundation :-

1. Collapsing of Foundation because of surpassing the bearing strength of soil
2. Collapsing of Foundation because of withdrawn of moisture from Soil all of a sudden
3. Collapsing of Foundation because of differential or unequal settlement
4. Collapsing of Foundation because of uneven progress and pattern of construction
5. Collapsing of Foundation because of movement of adjacent soil.

Collapsing of Foundation because of surpassing the bearing strength of soil:-

Ultimate bearing strength means ultimate load intensity that a soil can bear devoid of any shear failure of the Soil. The size of the footing with regard to length, breadth and diameter, is primarily based on the bearing strength.

A foundation/ footing of a structure must contain adequate size in order that the intensity of load directing via that footing from the structure to the soil below should not raise the bearing strength of that soil. If the bearing strength of soil is low or load operating is heavy and the size of the footing is relatively small than actual requirement then the load intensity (i.e. load per unit area say KN/sq.m. etc.) conveyed on the soil may be greater as compared to the bearing strength of the soil, for this reason a shear failure of soil will occur.

To provide perfect footing size, the safe bearing strength rather than ultimate bearing strength should be applied to obtain margin of safety against any accidental loading as well as abnormal behavior of the soil due divergence in its bearing strength. Safe bearing strength is nothing but ultimate bearing strength divided by a appropriate factor of safety usually varying from 2 to 4.

Collapsing of Foundation because of withdrawn of moisture from Soil all of a sudden :

It is one of the most crucial factors that should not be neglected. Moisture withdrawn occurs in the following ways :-

a) By draining water from the adjacent well through pump
b) By dewatering adjacent Pond
c) Reduction of ground water table close to the ground previously.

Since the soil usually comprises of soil solid, water and air and super structural load on soil is carried by the both soil solid and pore water, as soon as the pore water is withdrawn, it will produce voids inside the soil system around and at the bottom of the foundation soil that leads to subsidence of the soil together with supporting structure. As a result, the collapsing of foundation happens.

To get more details about other reasons for failure, go through the following link www.mycivil.engineer



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Published By
Rajib Dey
www.constructioncost.co
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How to resolve issues prior to foundation design

To make a perfect foundation design, the following vital points should be taken into consideration:-

Make sure that the foundations are maintained as extremely shallow, suitable with atmospheric impacts and strength of the surface soil; specifically in flooded ground. Excavation in fatally flooded ground seems to be costly and slow.

Get rid of costly and complicated shuttering details specifically in hardened rafts. Proper care must be taken to examine the build aptitude.

The economics of the design can be significantly impacted with various factors like drop in the piling costs, upgrading in ground treatment, progression in soil mechanics, etc and various standard solutions are now obsolete. So, it is necessary to evaluate construction costs and methods on a regular basis.

Designers should be well versed with the presumptions provided in design, the inconsistency of ground conditions, infrequent inapplicability of refined soil analyses and the utility of construction.

Make proper evaluation to check the consistency of the soil.

Impact of construction on ground properties, i.e. vibration from piling, degradation of ground disclosed with excavation in unfavorable weather conditions, deduction of overburden, seasonal difference in the water-table, compaction of the ground through construction plant.

Impact of deviating shape, length and inflexibility of the foundation, and the requirement for movement and settlement joints.

Consequences on finished foundations with sulfate attack on concrete, ground movements because of frost heave, reducible clays, and the impacts of trees; also alterations in local environment, e.g. new construction, re-routing of heavy traffic, foundation of plant in adjacent factories inducing impact and vibration.

Rapid but costly construction may be more cost-effective as compared to low-cost but slow construction to clients requiring quick return on capital investment.

Impact of new foundation loading on existing nearby structures.

To get more information, go through the following construction video Civilblog.Org

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Published By

Rajib Dey

www.constructioncost.co

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SO-Foundation, a powerful construction program for finding out the bearing strength of shallow foundation

Soil Office, the leading developer of various geotechnical engineering software, has created SO-Foundation. It is a powerful construction program that can be used to compute bearing strength of shallow foundations in view of both “shear failure” and “settlement”.

The software applied Hansen, Meyerhof, Vesic, Terzaghi and Eurocode methods to find out the shear failure. The are also several options to work out elastic and consolidation settlements.

The software also provides complete detailed reports.

Features - General

- Provides information on near about 20 soil layers.
- User can get notification on the common ranges concerning input parameters.
- Pressure isobars are computed and produced under footings.
- Defines bearing strength of shallow footings (Spread, Continuous and Mat) with various dimensions in view of both shear failure and settlement (Elastic and Consolidation).
- Estimate settlement according to the tolerable pressure.
- Estimate modulus of subgrade reaction.
- Estimate and creation of modulus of subgrade reaction contour on the footing surface.
- Export results to MS Excel format.
- Demonstration of calculation report containing adequate details.
- Formation of profiles for the preferred settings.
- Saving files with a smallest size.

Shear failure:

- Utilization of 5 methods, Eurocode, Hansen, Meyerhof, Terzaghi and Vesic.
- Modification of general factor of safety.
- Strength reduction factors are attributed for friction angle and cohesion, independently.
- Water effect is used with 2 methods.
- Inclusion of large footing effect in calculations.

Settlement:

• General
- Modification of permissible settlement by user’s will.

- Valid depth in settlement calculation is defined as the least amount of below:
a. Pressure isobars (based on each of the methods Boussinesq, Westergaard and Approximate 2V:1H) or a multiple of foundation width.
b. Depth of the rigid layer.

To download the software and gather more information, click on the following link soiloffice.com

Watch the following video for online demonstration.

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Published By
Rajib Dey
www.constructioncost.co
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Shaft3D – A powerful software for foundation design and analysis

Shaft3D software is created for simplifying the pile design process specifically for the drilled shafts or caisson type foundations. The software will allow you to perform multi tasking like shaft axial capacity analysis, lateral analysis and concrete design etc.

With Shaft3D, it is possible to design caisson foundations for windmills, transmission lines, utility lines or any other structure requiring drilled pier foundations quickly.

Shaft3D can enhance your productivity considerably through its windows-based, easy-to-learn graphical interface and its capacity to offer a complete solution for different types of analyses.

Given below, some useful features of the software :-

• International Design Codes: Compatible with various concrete design codes to finish your global projects efficiently.
• User Defined Parameters: There are various design options like shaft boundary conditions, choice of safety factors in end bearing, skin friction and pullout, choice of axial capacity methods and lot of others to fulfill numerous project specifications.
• Graphical Input of Soil Profile: Facilitates input of unrestricted number of soil layers, each with various unique set of soil properties graphically permitting you to visualize your soil profile.
• Soil Property Values: Offers a series of values of soil properties like cohesion, angle of internal friction with selection of the soil type authorizing you to complete a preliminary design devoid of detailed soil report.

• Load Cases and Combinations: Produces generally used load cases and combinations for shaft design that saves design time considerably.

• Multiple Analyses: Accomplishes axial capacity analysis, lateral analysis and concrete design in one combined surrounding.
• Axial Capacity Methods: Facilitates to choose from several axial capacity methods so that it is possible to fulfill the need of your company or client.

• Lateral Analysis: Accomplish lateral analysis with finite element analysis demonstrating vital information like deflections, shears, bending moments along the length of the shaft allowing you to explore with different “what-if” scenarios.
• Concrete Design: Execute concrete capacity design for axial loads and biaxial bending that offers you a complete geotechnical and structural solution.
• Rebar Layouts: Generates several rebar layouts with customization options.

• Material Quantities: Produces material quantities to perform precise cost estimates for your customers each time at each phase of the project.
• Detailed Design Sketches: Creates a detailed design sketch with plan, elevation and section to sum up the completed design efficiently.

• Multiple Reporting Options: Produces various types of customizable reports to utilize them for your internal or client requirements.

To know the additional features, go through the following link dimsoln.com

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Published By
Rajib Dey
www.constructioncost.co
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Soil mechanics and foundation engineering – An exclusive book for civil engineers

Dr. K. R. Arora, having 25 years of teaching experience, has written an exclusive book alias soil mechanics and foundation engineering. The book is available in PDF version.

The book is specifically designed for the undergraduate students as well as the students appearing for different competitive examinations and AMIE. A huge numbers of charts and tables are provided to make the text informative for practicing engineers.

Soil mechanics and foundation engineering (geotechnical engineering) is a part and parcel of civil engineering that witnesses a significant growth. The book is enriched with the most updated information in the field. The author has accumulated the material from different sources and demonstrated them in the form of a text.

The text is segregated into two parts. The first part sheds light on the basics of soil mechanics. The second part focuses on earth retaining structures and foundation engineering. The subject matter is explained in a rational and organized way.

The book comprises of the syllabi of undergraduate courses in soil mechanics and foundation engineering prescribed by most of Indian Universities and Institutes.

With the use of simple and coherent language, the author tries to narrate the basics for the students. Basic concepts have been emphasized throughout. The special emphasis is given on the complexities faced by the students. The book is supported with the extensive range of descriptive examples to present the application of the theory to field issues. Numerical problems, with answers, are provided for practice.

Some objective type questions are provided at the end of the each chapter.

The text is plentifully exemplified with diagrams and charts. Latest IS codes are abided by, as far as possible. References are provided at the end of each chapter. Both MKS and SI units are applied in this book.

Click on the following link to download the book Soil mechanics and foundation engineering

Read more

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Published By
Rajib Dey
www.constructioncost.co
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