Retaining walls shall be designed to withstand lateral earth and water pressures, the effects of surcharge loads, the self-weight of the wall and in special cases. When is a building consent needed? Under Schedule 1 of the Building Act , the construction of a retaining wall does not require a building consent when it. PDF | On Aug 6, , Moamen echecs16.info Raouf and others published Retaining Wall.
|Language:||English, Spanish, French|
|Genre:||Science & Research|
|ePub File Size:||28.83 MB|
|PDF File Size:||13.38 MB|
|Distribution:||Free* [*Register to download]|
RETAINING WALLS WITH METALLIC STRIP. REINFORCEMENT. ➢ Calculation of Active Horizontal and vertical Pressure. ➢ Tie Force. ➢ Factor of Safety. Design a cantilever retaining wall (T type) to retain earth for a height of 4m. The backfill is horizontal. The density of soil is. 18kN/m3. Safe bearing capacity of soil . Contents at a glance: 1. About Retaining Walls; Terminology. 2. Design Procedure Overview. 3. Soil Mechanics Simplified. 4. Building Codes and Retaining.
Salim Aldweik Optimal design of reinforced concrete retaining avails , Shravya Donkada and Devdas Menon This paper aims at developing an understanding of For delivering an acceptable design, today's design optimal design solutions for three types of reinforced practitioners increasingly rely on P C based programs concrete retaining walls, namely, cantilever retaining that require parameters, such as toe or heel lengths and stem widths. The process invariably involves a walls, counterfort retaining walls and retaining walls trial and error procedure. O b t a i n i n g a satisfactory with relieving platforms. Using genetic algorithms, design per se, does reveal its cost position against the parametric studies were carried out to establish optimal design. The present study therefore aims at heuristic rules for proportioning the wall dimensions developing an optimal design solution for reinforced corresponding to the minimum cost points.
The lateral earth hf! Types of concrete retaining walls of the retaining walls. Its distribution is typically triangular, least at the top of the w a l l and increasing towards platform.
Retaining wall with relieving platforms the bottom. The earth pressure could p u s h the w a l l is relatively new to Indian construction industry. Also, Such walls are k n o w n to provide an economical the groundwater behind the w a l l should be dissipated lightweight design solution for relatively tall by a suitable drainage system; otherwise, this could walls.
The retaining w a l l is s h i e l d e d f r o m 4,0 lead to an additional horizontal pressure on the wall. Also, the relieving platform carries the weight of the soil above it and any surcharge A s stated earlier, this study deals w i t h the following loading, transferring them as a 'relieving' moment types of retaining walls: to the vertical stem.
This aspect is the key to designing converting horizontal pressures from behind the such walls. This w a l l type is believed to be economical up to a height of about 7 m Figure la. Introducing transverse supports reduces h e e l , stem a n d other parts c o n s i d e r i n g the bending moments, w h e n the heights are large. Such supports, called counterforts, connect the stem w i t h the heel slab. This w a l l type is believed Estimation of earth pressure to be economical for heights greater than 7 m Figure l b.
Cpas 2. SBC Results of optimization 5. R e s t r i c t i o n s o n m a x i m u m a n d m i n i m u m The programs developed were a p p l i e d to generate reinforcement percentage a n d reinforcement optimal solutions for the three different types of walls spacing as per IS code 1 of various heights. The heights ranged from 5 m to 14 m i n the case of cantilever and counterfort walls, however 7.
Restrictions o n m a x i m u m shear stress i n the for the walls w i t h relieving platforms, the range was 5 m footing, stem and other parts based on concrete to 18 m.
It may 2 be noted that w h e n the height considered was greater This study used Genetic algorithms GA for carrying out than 14 m , no feasible solutions were possible for the searches within the design space.
G A is a heuristic search cantilever and counterfort retaining walls cases, as the method, w h i c h uses the process of natural selection for computed m a x i m u m bearing pressure o n the footing finding the global o p t i m u m.
These algorithms search a 8 exceeded the Safe Bearing Capacity of the soil, i. They first apply the principle of survival of the fittest to find better and better approximations. A t each This was also the case w i t h the w a l l w i t h r e l i e v i n g generation of values for design variables, a new set of platforms w h e n its height exceeded 18 m.
Feasible approximations is created by the process of selecting solutions are possible only w h e n the S B C is higher than individual potential solutions individuals according to the computed maximum bearing pressure on the footing.
G A does not use the gradient but uses the values of objective functions Tables 2,3 and 4 list the optimal solutions generated for and hence it can be used where the search space is the three w a l l types, considering M25 grade of concrete discontinuous.
The two dial gauges are fixed to magnetic holders and in two those are fixed magnetically to the large steel table. Now initial readings for both dial gauges are recording. To start the deformation time behavior, water is poured in the backfill side behind the wall and reading with time are simultaneously recorded, so, we have two curve one for vertical settlement of retaining wall and other for horizontal rotation of wall, it is believed that these two curves can describe the movement of wall in two directions.
It is customary to normalize the data so that it is well understand in terms of some specified dimension of wall. Thus the vertical settlement is normalized in terms of footing width or wall height H. The results apply where the initial condition is not Ko condition.
He demonstrated the active and passive theories by very careful tests. In these tests the walls were held against horizontal movement as the back fill was placed and the thrust against the wall was measured. The thrust was greater than the active thrust. Then the wall was released and permitted to move horizontally or rotate. After a movement of the top of the wall equal to only 0. This is very small amount of movement with angular rotation of only 0. On the other hand Bowles presented a table showing amount of horizontal translating to motive to the Ka condition, as shown in table 1.
From the foregone discussion it is intended to compare the movement of retaining wall with standard movement of retaining wall according to ranking and coulomb theories of acting and passive states, i. And as said before that careful studies conducted by Terzaghi about one century ago revealed that a horizontal movement of 0.
Retaining to our model the first one conduced was by using equal share of gypsum and soil, i. A crack in model glass after few hours led to the leakage of all perched water in tank. Never the less we have two figures simulating the movement that is figures 7 and 8. In these figures the displacement of retaining wall is presented in normalized form with time in minutes. The vertical settlement is shown in terms of settlement width of wall.
In figure 7 it can be seen that the total angular rotation wall is 0. The final number reached after about one week of soaking process is about 0. Due to the small relatively height of wall, this low rotation is expected as can be year although the gypsum content in base soil is considered terribly high.
At end of test and that is about one week after, uneven movement took place in terms of up and down Diyala Journal of Engineering Sciences, Vol. This could be due to the failure in glass of model which made the process to contain some leaching in addition to soaking process.
The water is kept into model no matter how leakage was. In order to explain these data, author has resorted to figure 3 which show the retaining wall in isotropic view. At point A the dial gauge measuring the vertical movement of retaining wall is installed by fixing it to large steel table. At point B the dial gauges measures the horizontal movement of wall is installed and fixed as in the case of the vertical movement. Now if we visualize that tip C settles alone downwards due to uneven collapse settlement the dial gauge at B will record positive movement of wall while that at tip A may measure zero settlement or may even record an upward movement if the center of rotation is at point between C and D.
On the other hand, if we have a settlement under point D only while point C remains still again due to uneven settlement then dial gauge at A may record a positive downward settlement while dial gauge at B may give negative records. In other words, due to uneven and differential collapse of retaining wall these fluctuations in curves of figures 9 and 10 is attributed to the movement of retaining wall under collapse settlement which in turn depends on the location of center of rotation between points C and D.
It is worth to mention here that the foregone explanations agree well with time of fluctuations. So these figures lead to a fact that collapse settlement of retaining wall founded over gypseous soil is totally no uniform and quite differential in nature unlike of most settlements.
Its worth to mention that Bowles stated that convert retaining walls have a tendency to tilt forward because of the lateral earth pressure.
But they can also tilt from base rotation caused by differential settlements. Occasionally, the base soil is of poor quality and with placement backfill typically the approach fill at a bridge abutment the backfill pressure produces a heel settlement that is greater that at the toe. A wall with a forward tilt does not give an observer much confidence in its safety. Unless the wall has a front batter it is difficult for it to tilt forward even a small amount without the tilt being noticeable.
It may be possible to reduce the tilt by overdesigning the stem, say, use ko instated of ka pressure and raise the location of resultant. This is a rather small value of settlement ratio. In addition, if we consider or take into account a large dimension of B.
The curves versus time for horizontal and vertical movements are shown up in figure 11 and In figure 11 the horizontal movement started to show up drastically after about one day and reaches to a maximum value of 0.
This amount is, as before, six times the movement required for ka condition due to the large base settlement of gypsum soil base. This residual value is still well beyond the ka value. When we compare time in which retaining wall starts to fluctuate in its movement in figure 9 and figure 10 we see that locate almost same time.
It is suggested to complete the vision and make another two tests but with gypsum content of 30 for both models. The second model is mixed with 2. In this way we may be able to compare between the two models the effect of cement on gypseous soil in case of retaining walls. Figure 14 shows the vertical movement of retaining wall, while fig.
Similarly fig. All curves are drawn as usual versus time in logarithmic scale. May someone think , if there exist a problematic soil , such as a collapsible soil , it is better to replace it than to take it away, improve it by some additions cement for example then get it back to original place to be used as a foundation soil. If clear gypsum free soil exists in nearby place, then it is meaningless to improve the gypseous soil by mixing it with cement then get it back in the first place.
But what if there is no nearby soil with good engineering properties or no tracks or transporting vehicles available or very expensive to transport to place, then the improvement of local soil is the best choice available at hand. The good engineering properties soil was available at distance of thousands of kilometers away from position in concern. Author's feet that same condition may exist if a civil engineer has encountered a case of retaining wall founded on gypseous soil.
In other words, the final test conducted does conform to reality, although may be rare, and remembering that local estates are becoming more expensive year by year and the choice of replacing the place with another is no valid today.
Retaining now to our curves, the following numerical values are deduced from those figure are summarized in table 2. They represent the maximum movement recorded for the two cases. From the initial look at those results it is quite dear that the addition of cement to gypseous soil base has greatly reduced both the horizontal and vertical movements together.
Of course, if leaching is included the movement wills definitely increases and thus the improvement obtained will be less. In this study it is desired to focus on the behavior of ordinary retaining wall founded over gypseous soil. Retaining walls are often used frequently when slope stability limitation stands against suitable or available space. There are many types of such walls. This study provides comprehensive aspects for movements of retaining walls when water percolates through foundation soil.
Lateral earth pressures are zero at the top of the wall and — in homogenous ground — increase proportionally to a maximum value at the lowest depth. Earth pressures will push the wall forward or overturn it if not properly addressed. Also, any groundwater behind the wall that is not dissipated by a drainage system causes hydrostatic pressure on the wall.
The total pressure or thrust may be assumed to act at one-third from the lowest depth for lengthwise stretches of uniform height. Unless the wall is designed to retain water, It is important to have proper drainage behind the wall in order to limit the pressure to the wall's design value.
Drainage materials will reduce or eliminate the hydrostatic pressure and improve the stability of the material behind the wall. Drystone retaining walls are normally self-draining.
As an example, the International Building Code requires retaining walls to be designed to ensure stability against overturning, sliding, excessive foundation pressure and water uplift; and that they be designed for a safety factor of 1. Gravity walls depend on their mass stone, concrete or other heavy material to resist pressure from behind and may have a 'batter' setback to improve stability by leaning back toward the retained soil. For short landscaping walls, they are often made from mortarless stone or segmental concrete units masonry units.
Earlier in the 20th century, taller retaining walls were often gravity walls made from large masses of concrete or stone. Today, taller retaining walls are increasingly built as composite gravity walls such as: Cantilevered retaining walls are made from an internal stem of steel-reinforced, cast-in-place concrete or mortared masonry often in the shape of an inverted T.
These walls cantilever loads like a beam to a large, structural footing, converting horizontal pressures from behind the wall to vertical pressures on the ground below.
Sometimes cantilevered walls are buttressed on the front, or include a counterfort on the back, to improve their strength resisting high loads. Buttresses are short wing walls at right angles to the main trend of the wall.
These walls require rigid concrete footings below seasonal frost depth. This type of wall uses much less material than a traditional gravity wall. Sheet pile retaining walls are usually used in soft soil and tight spaces. Sheet pile walls are driven into the ground and are composed of a variety of material including steel, vinyl, aluminum, fiberglass or wood planks.
Taller sheet pile walls will need a tie-back anchor , or "dead-man" placed in the soil a distance behind the face of the wall, that is tied to the wall, usually by a cable or a rod.
Anchors are then placed behind the potential failure plane in the soil. Bored pile retaining walls are built by assembling a sequence of bored piles , proceeded by excavating away the excess soil. Depending on the project, the bored pile retaining wall may include a series of earth anchors , reinforcing beams, soil improvement operations and shotcrete reinforcement layer.
This construction technique tends to be employed in scenarios where sheet piling is a valid construction solution, but where the vibration or noise levels generated by a pile driver are not acceptable.
An anchored retaining wall can be constructed in any of the aforementioned styles but also includes additional strength using cables or other stays anchored in the rock or soil behind it. Usually driven into the material with boring, anchors are then expanded at the end of the cable, either by mechanical means or often by injecting pressurized concrete , which expands to form a bulb in the soil. Technically complex, this method is very useful where high loads are expected, or where the wall itself has to be slender and would otherwise be too weak.
Soil-nailed walls soil reinforced in place with steel and concrete rods. Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of relatively slender elements — normally steel reinforcing bars. The bars are usually installed into a pre-drilled hole and then grouted into place or drilled and grouted simultaneously. They are usually installed untensioned at a slight downward inclination.
A rigid or flexible facing often sprayed concrete or isolated soil nail heads may be used at the surface.