Lean concrete and flowable concrete are terms used to describe low-grade concrete slurry that is used in a variety of construction projects. In some ways the two terms are interchangeable, both describing concrete made with lesser ingredients, but there are some differences in how the two are used. Lean concrete tends to be more long-lasting than flowable concrete, which is often temporary.
Lean Concrete
Lean concrete is made with low cementitious material content. This means that it does not have many of the heavy, high-density rock and sand elements that normal concrete has. Instead, it can use a mixture of standard concrete materials, reclaimed and crushed concrete, discarded sand and recycled ash. This makes lean concrete very cheap in nature and simple to make and use.
Uses
Main function of the lean concrete is to provide the uniform surface to the foundation concrete and to prevent the direct contact of foundation concrete from the soil.
Lean concrete is used under the foundations.
It is good for providing a flat bottom in uneven or dirt terrain.
Lean concrete has a lower level of cement in it, which is why it’s mostly used for fillings or under the foundations, to keep it protected from the soil.
Lean concrete is used to provide a level surface , where main foundation (raft, isolated or any other type) can be placed.
Another purpose is protection of main foundation from soil below, as moisture or other chemicals in soil like sulphates may attack concrete and can weaken it.
Flowable Concrete
Flowable fill concrete is a self-compacting cementitious slurry consisting of a mixture of fine aggregate or filler, water, and cementitious material which is used as a fill or backfill in lieu of compacted-soil backfill. This mixture is capable of filling all voids in irregular excavations and hard to reach places (such as under undercuts of existing slabs), is self-leveling, and hardens in a matter of a few hours without the need for compaction in layers.
Flowable fill is sometimes referred to as controlled density fill (CDF), controlled low strength material (CLSM), lean concrete slurry, and unshrinkable fill.
Flowable fill materials will be used as only as a structural fill replacement on VA projects. Unless otherwise noted, flowable fill installed as a substitution for structural earth fill, shall not be designed to be removed by the use of hand tools.
The materials and mix design for the flowable fill should be designed to produce a comparable compressive strength to the surrounding soil after hardening, making excavation at a later time possible to produce the compressive strength indicated for the placed location, as determined by the Engineer.
Purposes
Like lean concrete, flowable concrete or flowable fill is used for sub-bases and subfooting as well as abandoned wells and cavities. But flowable concrete is more associated with backfill projects where the concrete will be removed in several months when projects are completed. Because it will be taken away, it may be made of cheaper and less durable materials than lean concrete.
Best sites for PMP, PMI-ACP and CAPM certification exams
There are lot of good blogs and sites are available in the internet for learning PMP certification exams.
Project Management Article from Whizlabs – This is one of the popular blog for Project Management courses. Whizlabs offers PMI-ACP, PMP, CAPM certification exam practice questions and self-study training materials in their blog.
www.rmcls.com/ – This site is maintained by Well known author and trainer Rite Mulcahy. It is very useful to know the latest update on PMP exams.
www.oliverlehmann.com/ – Oliver is one of the most popular PMP author and instructor for the PMP exam. You can find very useful information related to PMP exam in his site.
kavitasharma.net/blog-archive/ – Kavitha Sharma is one of the popular independent PMP trainer in India. She writes about latest updates in PMI and guides user to prepare effectively for the PMP certification exams.
www.pmbypm.com/ – This blog is maintained by PMP trainer Praveen Malik. He is a certified Project Management Professional (PMP®) with a rich 19 years of experience. He provides help for the PMP students by educating them on the PMP topics. You will find lot of useful information about PMP in his blog.
pmzilla.com/ -This is one of the most popular forum for preparing PMP certification exam. If you have any questions related to PMP, this forum is the right place to start with.
www.pmhangout.com – This is one of the good forum for discussing the PMP and CAPM certification exam.
www.stellman-greene.com/ – Stellman is the author for best seller Head First PMP book. He also releasing his latest book for CAPM exam. His site is very useful with tons of details about the PMP exams. It is good site.
preparepm.com/index.html – Edwel is an independent instructor who take training for PMP exams. There is lot of free questions for PMP in his site. The questions are based on the PMBOK 5th edition. Also you can find lot of information on his site Edwel.
www.pmstudy.com/ – This site offers more practice questions for the PMP exams. This site also a good for preparing PMP exams.
www.justpmp.com/ – This site has no special information about the PMP exams. Normall training details for Project Managements Professional (PMP) exam information.
www.deepfriedbrainproject.com – This PMP site has lots of useful information and techniques to crack the PMP exams. It would be useful for your PMP, CAPM and PMI-ACP preparation.
www.examspm.com/blogs/ – This blog has good amount of articles about the PMP preparation. They also offer free training for the PMP courses.
http://www.pmexamsmartnotes.com/ – This blog has very good information about the PMP certification exam and have lot of free resources for preparing PMP certification exam.
edward-designer.com/web/pmp/ – Edward Chung shares his experience and resources on getting the PMP® Certification, PMI-ACP®, ITIL® v3 Foundation and Zend PHP.
www.project-management-prepcast.com/ – This is another site where complete PMP related courses are offered. You can find all the project management certification exams details are in the site.
www.techrepublic.com –7 great IT certification exam simulators for project managers
www.brainbok.com – This site offers only PMP related training, but little expensive compared to other companies.
www.whizlabs.com/project-management-professional-pmp/ – Whizlabs is pioneer in the PMP exam training materials. They have recently updated their content to meet the Jan 2016 PMI updates. Their sit has both, practice questions and self-study training materials.
www.greycampus.com/ – Grey Campus is one of the leading online training provider. You can get good training courses in their website.
When it comes to job interviews, first impressions are everything. You probably know to avoid certain faux pas–like being late, or saying something mean to the receptionist. But you also need to stay away from giving clichéd answers that will discourage your interviewer from advancing you to the next stage.
As a hiring manager (and the founder and CEO a staffing firm), here are some of the most common ones I hear:
“I’m an overachiever”
I’m a big believer in word choice and semantics–people meaning what they say, and saying what they mean. When I hear this, I believe you are an underachiever, or you’re a decent worker, but not a superstar.
Here’s what I mean: Being labeled an overachiever means that people underestimated you. If you overachieve, that means you did more than people thought you could. To me, this raises the question, why did they believe that you were limited in your abilities?
“I give 150 percent”
Whenever I hear this phrase, I always say, “I think you need to recalibrate.” I can only give you 100 percent. I can’t give you 150 percent of me, because there isn’t one and a half times of me. When you say something like this (especially without any specific examples to back it up), it makes you sound disingenuous, and you’ll probably end up over-promising, and under-delivering. This is not something that hiring managers want.
“I really love this company”
Really? Tell me, what do you know about the company? Is it more than the small bit you reviewed online? Any interviewer will assume you applied for the job because you like the company, so you don’t need to state the obvious. But you should know much as you can know without actually working there, which requires you to look beyond the company website. You need to understand what you can bring to the company, and how that ties it on their mission and overall objective.
Ask questions about why the people working there think it’s a great place. Find out where they believe the company can improve. Most importantly, think and ask questions to help you form opinions, not just for the sake of asking questions. As a hiring manager, I want you to tell me that you’ve done the research and talked to people because that’s the only way for you to understand what we’re building and creating.
“I’m hard working, I’m a team player, I’m committed”
You might think this is what the person on the other end wants to hear. I’m telling you that it’s not.
This is what I want to hear: “I will outwork and outproduce anyone else on this team. I will take on extra education to grow faster than my peers. I will put in time beyond standard business hours if and when necessary to achieve goals, and to cross-train in skills that other people have.”
But people won’t say those things because most people aren’t willing to execute them later on. To clarify, I’m not looking for people who want to work a million hours. I want people to be honest and for people to articulate what they bring to the table, and then deliver on it. In any relationship, if you lie about who you are and what you’re willing to do, it usually catches up to you. Always tell the truth.
“I’m extremely detail oriented”
If that’s a true statement, you better know the minute details of your job and your team. What happened last month, last quarter, and last year? Why were there problems and what was the cause of the successes?
As a hiring manager, I want to see concrete evidence of that. That means no typos in your resume and involvement in projects and deliverables that showed your attention to detail. As a candidate, the onus is on you to prove that to me.
“I feel like this is a place where I can learn and grow”
Okay. Now tell me what’s in it for us, the company? What are you going to contribute? We make money by growing revenue or cutting expenses; what are you going to do to move us in that direction, and how? This kind of answer to the question is focused on you, rather than on the company–and most interviewees tend to focus on themselves and what they want.
When you’re interviewing for a role, you should always focus on the company and what the company can gain by employing you. Yes, the advice seems obvious, but you’d be surprised how many people don’t follow this advice. Remember, you’re there to convince the company that you’re the best solution to their problem, that you’re the best person to fill their vacancy. Focus on that, and you’ll be surprised at how far you can go.
5 proposed designs for O’Hare airport’s huge expansion
Some of the biggest architecture firms in the world are competing for the contract, which will transform one of North America’s air traffic hubs.
Chicago’s O’Hare airport is one of the busiest airport in the U.S., and it’s only growing. The city recently approved a $8.5 billion expansion, which will balloon the airport’s indoor footprint from 5.5 million to 8.9 million square feet and require over 60,000 full-time workers to complete by 2026.
Now, as part of a public review process, the city has shared the five new terminal concepts for the first time, developed by the architecture firms Fentress-EXP-Brook-Garza, Foster Epstein Moreno, Studio ORD, Skidmore, Owings & Merrill, and Santiago Calatrava.
The public proposals share many similarities: They are all buildings with sprawling footprints to connect across O’Hare’s terminals, with white bones, undulating ceilings, and windows covering every available surface. Their differences appear to be formal rather than functional, with few quibbles over the optimal flow of 200,000 human bodies trudging through body scanners daily.
But the designs are still fascinating to compare, and a few big differences definitely stand out.
The architects at Foster Epstein Moreno JV imagine the terminal as three straight tubes that lead to a single grand view of the runways, creating “a theater of aviation.” The giant, arched panorama would certainly be a sight to behold, but I suspect the inevitable influx of vendors could ruin sight lines to this scene throughout most of the terminal. I’m curious, could you ever actually take in that view all in at once?
Studio ORD, led by Chicago architect Jeanne Gang, shared a three-pronged design that Curbed points out is likely a nod to the city’s river system. It features the surprising use of wood beams across the entire ceiling–a material you don’t often find in airports or in buildings that range in the millions of square feet. Coupled with organically curved, branching interior columns, the effect seems to be that of standing beneath a calming canopy of trees rather than inside a stifling airport.
Meanwhile, Skidmore, Owings & Merrill LLP–the same firm that brought Chicago the Willis Tower and the Hancock Building–proposed a glass-encased orchard at the center of the building, seeming to tease onlookers who would really prefer to be outside, vaping in nature. The green space is actually intended to be public, but one frame does feature a single traveler, enclosed in a glass box, with their feet up in a single hammock–as hundreds of grumps walk by in what I can only assume is seething, jealous rage.
Santiago Calatrava, LLC–perhaps most famous for the Oculus in New York City–imagines a future hotel and shopping complex complete with an expansive network of outdoor walkways (ahem, Chicago has a lot of winter, architects), but for the core indoor terminal area, it leverages Calatrava’s very recognizable architectural signature: an arrowhead footprint and fishbone ceiling.
Fentress-EXP-Brook-Garza didn’t see Calatrava’s proposal in advance, of course, but its proposal almost seems to answer back to it: “I can do exactly what you did, but without all the symmetry.” This proposal creates a space that twists more like a river, with roof supports that fly overhead like contrails rather than fishbones.
At this point, knowing what we do about these ideas–which is to say, very little–all we can really do is critique their look and feel. And they look and feel largely the same.
The public was able to vote on its favorite designs, but it’s unclear how, if at all, their votes will affect the final winner (the runner-up will also create a few new buildings at O’Hare, too). In fact, as the Chicago Tribune points out, the Mayor’s office has been entirely unclear on who is making a final call on these designs, at all. In any case, Mayor Rahm Emanuel is supposed to announce a winner before he leaves office this May. And whatever is chosen, it’s probably a huge upgrade from the O’Hare we have today.
Concrete vibration – The why and how of consolidating concrete
What factor has a greater effect on concrete compressive strength than any other? Most engineers would say water-cement ratio … as water-cement ratio increases strength decreases. Duff Abrams showed this in 1919, and Abrams’ law is the principle behind most concreting proportioning methods used today. But Abrams ran his tests on fully consolidated concrete.
Unless concrete is properly consolidated, voids reduce strength regardless of the water-cement ratio. And, as shown in Figure1, the effect is significant.
Right after it’s placed, concrete contains as much as 20% entrapped air. The amount varies with mixtype and slump, form size and shape, the amount of reinforcing steel, and the concrete placement method. At a constant water-cement ratio, each percent of air decreases compressive strength by about 3% to 5%. Consolidating the concrete, usually by vibration, increases concrete strength by driving out entrapped air. It also improves bond strength and decreases concrete permeability.
Figure 1. Degree of consolidation can have as much effect on compressive strength as water cement ratio. Low-slump concrete may contain up to 20% entrapped air when placed.
Vibration is a two-part process
How does vibration consolidate concrete? Figure 2 shows it to be a two- part process. A vibrator creates pressure waves that separate aggregate particles, reducing friction between them. Piles of concrete flat-ten as the concrete flows around reinforcing steel and up to the form face. Large voids (honeycomb) disappear. But making the concrete flowable doesn’t finish the compaction proces s. Almost simultaneously, a second stage starts to occur as entrapped air bubbles rise to the surface. This deaeration process continues after the concrete has flattened out. Until both vibration stages are complete, the concrete isn’t fully consolidated. If the vibrator is removed too soon, some of the smaller bubbles won’t have time to rise to the surface. Vibration must continue until most of the air entrapped during placement is removed. It’s usually not practical, though, to remove all the entrapped air with standard vibrating equipment.
Figure 2. A vibrator consolidates concrete in a two-part process. The first waves liquify the concrete so it flows better and the continuing waves knock out air bubbles.
Different vibrators for different jobs
The earliest form of equipment used as a vibrator was a rod stuck into the concrete, pushed down and pulled up. Rodding works for concretes with slumps greater than 3 inches, but it’s rarely used because of the costly labor required. Because rodding doesn’t put extra pressure on forms, howe ve r, it has helped more than one contractor complete a concrete pour when forms were bulging. The most common vibrator used is the electric, flexible shaft type. Other types include electric motor-in- head, pneumatic, and hydraulic. Vibrator output, usually expressed as a frequency, is controlled in a different way for each type of vibrator:
An electric vibrator uses voltage.
A pneumatic vibrator uses air pressure.
A hydraulic vibrator uses pressure and flow rate of hydraulic fluid.
On the jobsite the contractor can check the operating performance of his equipment by measuring frequency. If it’s low he should check for voltage fluctuations, air pressure losses, or hydraulic pressure drops. The type of vibrator must match the requirements of the concrete and the jobsite (Figure 3). Frequency rates determine the amount of vibration time required to complete the two-stage consolidation process. In the 1960s, vibration frequencies were much lower. To compact a 1⁄2-inch-slump concrete took 90 seconds at 4,000 vibrations per minute (vpm), 45 seconds at 5,000 vpm, and 25 seconds at 6,000 vpm. Today’s typical frequency of 15,000 vpm requires only 5 to 15 seconds of vibration time. Internal vibrators chosen for most jobs have a frequency of 12,000 to 17,000 vpm in air. The common flexible shaft-type vibrator reduces its frequency by about 20% when immersed in concrete. Motor-in- head types provide a constant frequency when in air or concrete.
Figure 3. The vibrator head must fit between the rebars and have a high enough frequency to quickly consolidate the concrete.
How to use an internal vibrator
Producing a dense concrete without segregation requires an experienced vibrator operator. Inexperienced operators tend to merely flatten the concrete because they don’t vibrate long enough to deaerate the concrete. Undervibration is more common than over vibration because of a worker’s effort to keep up with the concrete or to increase productivity. The operator can judge whether or not vibration is complete by watching the concrete surface. When no more large air bubbles escape, consolidation is adequate. Skilled operators also listen to the pitch or tone of the vibrator motor. When an immersion vibrator is inserted in concrete, the frequency usually drops off, then increases, becoming constant when the concrete is free of entrapped air. Never use a vibrator to move concrete laterally. Concrete should be carefully deposited in layers as close as possible to its final position in the form. As each layer is placed, insert the vibrator vertically. The distance between insertions should be about 11⁄2 times the radius of action (usually 12 to 24 inches). Radius of action is a distance from the vibrator head within which consolidation occurs. It varies with equipment and concrete mix.
Walls and columns
Special techniques are necessary to blend layers of concrete in walls and columns. Let the vibrator penetrate quickly to the bottom of the layer and at least 6 inches into the preceding layer. Then move the vibrator up and down, generally for 5 to 15 seconds, to blend the layers. Withdraw the vibrator gradually with a series of rapid up and down motions.
Elevated beams and slabs
Beams and joists placed monolithically with slabs should be vibrated separately before slab placement. Place the slab concrete after vibrating the beam, but before the beam concrete is set. Allow the vibrator to penetrate through the slab into the previously placed beam to blend the two structural elements.
Undervibration vs Overvibration
Undervibration is far more common than overvibration. Good quality normal- weight concrete is not readily susceptible to the problems caused by overvibration, so when in doubt, vibrate more. The problems associated with undervibration include:
Honeycombing
Excessive entrapped air
Sand streaks
Cold joints
Subsidence cracking
The problems associated with overvibration include:
Segregation
Sand streaks
Loss of entrained air
Form deflection
Form damage or failure
Overvibrating, because it causes entrained air loss, might be expected to decrease freeze-thaw resistance. Research results don’t bear this out, however. In one study, overvibration of low- slump, air- entrained concrete had no effect on freeze-thaw resistance. Overvibration should not be a concern unless high- slump, improperly proportioned concrete is being placed.
Vibrating around congested reinforcement
To provide good concrete- to- steel bond, vibration is especially important in areas congested with rebar. Vibration alone doesn’t solve the problem. Other actions must be taken to help complete concrete consolidation, such as:
Using admixtures to increase flowability but limit segregation
Changing mix proportions or ingredients to increase flowability
Designing the reinforcing for ease of concrete placing
Figure 4. Vibration alone won’t consolidate concrete adequately when reinforcing is congested. To ensure adequate consolidation it may be necessary to use superplasticizers, reduce aggregate maximum size, or adjust rebar spacing.
To achieve proper consolidation by internal vibration in congested areas, the designer should provide obstruction-free vertical access of 4×6-inch minimum openings to insert the vibrator. Horizontal spacing of these openings should not exceed 24 inches or 11⁄2 times the vibrator’s radius of action. Engineers designing congested reinforcement should also design for proper consolidation, otherwise contractors can’t always guarantee adequate concrete to steel bond (Figure 4).
References
1. “Guide for Consolidation of Concrete,” ACI 309R-87, ACI Materials Journal, September-October 1987, American Concrete Institute, Box 19150, Detroit, Michigan 48219. 2. Whiting, D., G. W. Seegebrecht, and S. Tayabji, “Effect of Degree of Consolidation on Some Important Properties of Concrete,” SP-96, Consolidation of Concrete, American Concrete Institute. 3. Olsen, Mikael, “Energy Requirements for Consolidation of Concrete During Internal Vibration,” SP-96, Consolidation of Concrete, American Concrete Institute. 4. Troxell, Davis, & Kelly, Composition and Properties of Concrete, McGraw- Hill, New York, New York, 1968.
Road safety audit is the formal examination of existing roads, future roads or various sorts of traffic projects by any independent group of trained expertise. They examine the deficiencies in road safety. There are various stages of road safety audits. Number of stages depends on the number of stages in a road project before completion.
Feasibility study phase
Preliminary design phase
Detailed design phase
Pre-opening phase
In service phase
Feasibility Study
In feasibility study phase, trained specialist study and evaluate the results of following questions;
What is the scope of this project?
How many choices of routes available?
What will be the impacts on the existing transportation system?
Which design should be selected as a design standard for that road?
How long this route could be continued?
Which location will be the best location of interchanges?
Number of lanes required for managing maximum average daily traffic?
Where to provide the route terminals?
What will be the effects on the environment?
Control access
Technical team works on these questions step by step and at the end gives the most feasible solution possible.
Preliminary Design Stage:
Preliminary design is the second stage of road safety audits. In this stage designs of roads are carried out. As preliminary phase, therefore designing is not carried out in a very detailed. Following are road designs that are done in this phase;
Alignment of horizontal and vertical curves
Width of land and shoulder
Layout of intersection
Provision of super elevation and side slopes with pavements
Provision of overtaking lanes
Provision of separate way for pedestrians and cyclists.
Safety arrangements during construction on site
Provision of sign boards.
Design of Link roads
Space management
Detailed Design Stage
After the completion of 2nd stage, designs are carried out in detail. Following are the road designs that completes at the end of this stage;
Signals
Sign boards
Line marking
Lighting
Intersection details
Delineation
Provision of shoulders
Management of traffic during construction
Design of road drainage system
Provisions of way for road user groups. For example, pedestrians, cyclists, vans, trucks etc.
Provision of slopes.
Provision of road side objects
Pre-Opening Stage
In this phase technical audit team drive through the completed project. During drive, they observe the provision of safety level, quality, sign boards, road material and all other aspects that they took under consideration during the preliminary survey and detailed design phase. They came on the site during different weather conditions like during day time, night, etc… after the completion of survey they wrote a report on it and deliver it to the main authority.
In-service:
After the pre-opening examination, road is opened for public and during that still technical team remains active and they observe the working of safety features during heavy traffic.
Flexible pavement differ from rigid pavement in terms of load distribution. In flexible pavements load distribution is primarily based on layered system. While, in case of rigid pavements most of the load carries by slab itself and slight load goes to the underlying strata.
Structural capacity of flexible pavement depends on the characteristics of every single layer. While, the structural capacity of rigid pavements is only dependent on the characteristics of concrete slab. This is so, because of low bearing soil capacity of underlying soil.
In flexible pavements, load intensity decreases with the increase in depth. Because of the spreading of loading in each single layer. While, in case of rigid pavement maximum intensity of load carries by concrete slab itself, because of the weak underlying layer.
In flexible pavement deflection basin is very deep, because of its dependency on the underlying layers. While in case of rigid pavement, deflection basin is shallow, this is because of independency of rigid pavement on the underlying layers.
Flexible pavement has very low modulus of elasticity (less strength). Modulus of elasticity of rigid pavement is very high, because of high strength concrete and more load bearing capacity of the pavement itself. Than compared to flexible pavements.
In flexible pavements, underlying layers play very important role. Therefore, more role are playing only underlying layers. In case of rigid pavements, slight function of underlying layers. Maximum role is playing by the top layer (that is slab) by itself. Therefore, minute part is taking by sub layers.
This spreadsheet computes lateral pressure against retaining wall due to vertical surcharge area loads. It handles multiple area loads and uses theory of elasticity equations developed by Boussinesq. Subsequently, the spreadsheet calculates shear force and bending moment diagrams. Worksheet is protected but without password.
Retaining walls must be reinforced in order to be effective. Too many forces are at work against a retaining wall that could cause it to tumble over if it is not reinforced correctly.
“WALLPRES” is a spreadsheet program written in MS-Excel for the purpose of determining the horizontal (lateral) pressures to be applied to walls from various types of loading including lateral earth pressure, hydrostatic pressure, as well as uniform, point, line, and strip surcharge loadings.
This program is a workbook consisting of five (5) worksheets, described as follows:
Doc – documentation sheet
Wall Soil Pressures – Static horizontal soil pressure against wall
Wall Pressures from Point Load – Horizontal pressures on rigid wall from point surcharge load
Wall Pressures from Line Load – Horizontal pressures on rigid wall from continuous strip surcharge load
Wall Pressures from Strip Load – Horizontal pressures on rigid wall from continuous line surcharge load
Program Assumptions and Limitations:
1. This program is based on the following references:
a. NAVFAC DM-7.02 Manual – “Foundations & Earth Structures” (1986)
b. NAVFAC DM-7.01 Manual – “Soil Mechanics” (1986)
c. Army TM 5-818-1 / Air Force AFM 88-3, Chap. 7 (Oct. 1983) “Soils and Geology Procedures for Foundation Design of Buildings and Other Structures”
d. “Foundation Analysis and Design” (2nd Edition), by: Joseph E. Bowles McGraw-Hill, 1977
e. “USS Steel Sheet Piling Design Manual” – updated and reprinted by FHWA with permission (July 1984)
f. “Lateral Soil Pressure on Retaining Walls and Embedded Exterior Walls of Structures” Report U7-PROJ-S-RPT-STRU-6001, by: Sargent & Lundy, LLC (Feb. 26, 2009) for South Texas Project Units 3 & 4, Project No.: 12462-003
2. The resulting pressures obtained from the worksheets in this workbook can be used in the design of the stems of either cantilever or propped cantilever retaining walls, as well as for long walls of tanks and pits.
3. The equations used in the “Wall Pressures from Point Load” and “Wall Pressures from Line Load” worksheets are from References “a” through “e” above, utilizing original (1885) Boussinesq Equations modified to correlate with experimental test results. The Boussinesq equations assume the that wall is rigid and does not move, and that the wall is perfectly smooth (no shear stress between wall and soil). Thus, the equations overestimate the wall pressures for flexible walls by up to a factor of 2.
4. The equation used in the “Wall Pressures from Strip Load” worksheet is from References “d” and “e” above. Again, this equation assumes that the wall is rigid (does not move), which overestimates the wall pressures for flexible walls by up to a factor of 2. Thus, the factor of 2 appears in the numerator of this version of the equation. Other references may cite this equation without the factor of 2, which would normally be more applicable for flexible walls which are able to move at top.
5. This program contains “comment boxes” which contain information including explanations of input items, etc. (Note: presence of a “comment box” is denoted by a “red triangle” in the upper right-hand corner of a cell. Merely move the mouse pointer to the desired cell to view the contents of that particular “comment box”.)
