Sheet Pile Walls "article"

Sheet piles are a temporary structures used to retain a soil or water for aspecific period of time, to build a structure in the other side of this wall.For example; if we want to build a structure with three basement floors (underground) and this structure surrounded by other structures, when the excavation process starts, if the soil under the surrounding structures doesn’t retained by a sheet pile, this soil will fail and will moves to the excavation site, and the structure above this soil may collapse suddenly, so before establishment of excavation process, sheet pile must be constructed to retain his soil and prevent it from fails and after completion of constructed the structure , we can remove this sheet pile because it’s function was end.Another example; if we wanna build a structure in the sea (waterfront structures)we can use sheet piles to retain sea water from flowing to the required area, and then withdraw the water confined between sheet piles and thereby build the required structures, finally remove sheet piles because there functions were end.The following figures are some explanation of the applications of sheet piles and the shape of sheet pile itself:

Notes:

1.  Sheet piles may be made from steel, concrete or wood.

2.  As seen in the above pictures, sheet piles must penetrates a specified distance in earth (from both sides) to be stable against applied lateral loads,this depth called depth of penetration, and the following figure explain  the main parts of sheet piles:

The line at which the sheet pile starts penetrating in soil from both sides is known by dredge line, and the depth of penetration of sheet pile under this line is D: depth of penetration.

Designing of sheet piles mainly is to calculate the depth of penetration D and determining the section of sheet pile as will be discussed later.

Types of Sheet Piles

There are two main types of sheet piles:
1.  Cantilever Sheet Piles.
2.  Anchored Sheet piles.

Settlement and Allowable Bearing Capacity in the soil under shallow foundation "article"

the allowable settlement of shallow foundations may control the allowable bearing capacity.The
allowable settlement itself may be controlled by local building codes.

For example; the maximum  allowable settlement for mat foundation is 50 mm, and 25 mm for isolated footing.These foundations should be designed for these limiting values of settlement (by calculating the allowable bearing capacity from the allowable settlement). thus, the allowable bearing capacity is the smaller of the following two conditions:

The settlement of a foundation can be divided into two major

categories:

a)  Immediate or elastic settlement (Se):

Elastic or immediate settlement occurs during or immediately after the application of the load
 (construction of structure) without change in the moisture content of the soil.


b)  Consolidation Settlement (Sc) :

Consolidation settlement occur over time, such that pore water is extruded from the void spaces of saturated clayey soil submerged in water.Consolidation settlement comprises two phases: Primary and secondary. To calculate foundation settlement  (both elastic and consolidation), it is required to estimate the vertical stress increase in the soil mass due to the net load applied on the foundation .

Determining the number of soil boring in the construction site " Article"

There is no hard-and-fast rule exists for determining the number of borings are to be advanced. For most buildings, at least one boring at each corner and one at the center should provide astart.
 Spacing can be increased or decreased, depending on the condition of the subsoil. If various soil strata are more or less uniform and predictable, fewer boreholes are needed than in nonhomogeneous soil strata.

The following table gives some guidelines for borehole spacing between for different types of structures:

Procedures for Sampling Soil "Article"

There are two types of samples:

A- Disturbed Samples: 

These types of samples are disturbed but representative, and may be used for the following types of laboratory soil tests :
1- Grain size analysis.
2- Determination of liquid and plastic limits.
3- Specific gravity of soil solids.
4- Determination of organic content.
5-Classification of soil.
6-But disturbed soil samples cannot be used for consolidation, hydraulic conductivity, or shear tests, because these tests must be performed on the same soil of the field without any disturbance (to be representative)
The major equipment used to obtain disturbed sample is (Split Spoon) which is a steel tube has inner diameter of 34.93 mm and outer diameter of 50.8mm.

B- Undisturbed Samples: 

These types of samples are used for the following types of laboratory soil tests:

1- Consolidation test.
2-Hydraulic Conductivity test.
3- Shear Strength tests.
These samples are more complex and expensive, and it’s suitable for clay, however in sand is very difficult to obtain undisturbed samples. The major equipment used to obtain undisturbed sample is (Thin-Walled Tube).

Degree of Disturbance
If we want to obtain a soil sample from any site, the degree of di
for a soil sample is usually expressed as

equation

AR = area ratio (ratio of disturbed area to total area of soil)
Do = outside diameter of the sampling tube.
iD= inside diameter of the sampling tube.

If (AR) ≤ 10% → the sample is (UNDISTURBED)
If (AR) > 10% → the sample is (DISTURBED)

example

Compressive Test For Paste Cement Cubes 50mm With Different w/c Ratio "Report"

INTRODUCTION

This test method coves determination of the compressive strength of cement mortars , using  2 in (50 mm ) cube specimens .

 APPARATUS

In this test we will use equipment  as follow :

1) weights or weighing device .

2) glass graduate .

3) specimens molds : thre cubes of (50 mm) side .

4) mixer ( electrically driven mechanical mixer of the type equiped with paddle and mixing bowl ) .

5) testing machine .

6) tamper and trowel .

 And the following pictures shows this apparatus 

MATERIALS

graded standard sand should be used ( c778 ) with cement in the proportion  ( 1 cement : 2.75 sand ) by weight .

in this report we used water-cement ratio  as follow :

 0.45  , 0.5 , 0,55  , and  0,6  w/c  ratio .

PROCEDURES

 

 A- preparation of morter

1) weight (300)gm of cement and prepare the corresponding weights of standard sand and water.

2) place the dry paddle and the dry bowl in the mixing position in the mixer. then introduce the materials for abatch into the bowl and mix in the following manner .

3) place all the mixing water in the bowl and add the cement to the water , then start the mixer and mix at the low speed (140+or- 5  r/min ) for 30 second. add the entire quantity of sand slowly over a(30 s) period , while mixing as slow speed.

stop the mixer , change to medium speed (285+10 r/min) and mix for 30 second . stop the mixer and let the morter stand for 1.5 min . during the first (15 s) . of this interval , quickly scrape down into the batch any morter that may have collected on the side of the bowl .and finish by mixing for (1 min ) at medium speed .

B-molding test specimens

1) thinly cover the interior faces of the specimen molds with oil .

2) start molding the specimens within atotal time of not more than 2.5 min after completion of mixing.

3) place alayer of morter about 25mm (half the depth of the mold ) in all the cube specimens .

4) tamp the morter in each cube 32 times (4*8) , about 4 rounds < each round to be at right angles to the other .

5) the 4 rounds of tamping shall be completed in one cube before going to the next .

6) when the tamping of the first layer in all cubes is comleted , fill the molds with the remaining morter and tamp as specified for the first layer .

7) cut off the morter to a plans surface with astraight edge.

8) keep the molds in a moist room for 20-24 houres then open them and keep the specimens in a water basin for aweek .

c- testing specimens

1) after 7 days ( +3 hours), take the specimens out of the basin , dry them with a clean cloth , put them , one after the other in the testing machine.

2) the cubes must be put on one side , using extra steel plates up and down the specimen.

3) start loading in speed of 1.4 kn/sec or (350 kg/cm^2 ) in  a- minute .

4)when failure , record load and the compressive strength .

CALCULATIONS

 

now we will determine the compressive of every sample different w/c ration .

-The first sample with  0.45  w/c ratio  .

NO.CUBE	LOAD (KN)	COMP.STRENGTH        (MPa)_____	STRESS  WITH (kg/cm^2)	Weight (g)
1	51.7	20.68	210.805	283
2	50.6	20.24	206.32	281

- Average  comp -stress = 210.805+206.32 /2  = 208.563  kg/cm^2   for  0.45 w/c .

    The second sample  with  0.55 w/c ratio :-

NO.CUBE	LOAD (KN)	COMP.STRENGTH        (MPa)_____	STRESS  WITH (kg/cm^2)	Weight (g)
1	54.262	21.505	221.25	280
2	49.907	19.963	203.49	275

Average  comp- stress =  221.25+203.49  / 2   =  212.37 kg/cm^2  , for  0.5 w/c

-The third sample with 0.55 w/c ratio :-

NO.CUBE	LOAD (KN)	COMP.STRENGTH        (MPa)_____	STRESS  WITH (kg/cm^2)	Weight (g)
1	55.467	22.187	226.165	280
2	37.196	14.879	151.665	275

-  Average comp-stress = 226.165+151.665   /2  =  188.915  kg/ cm^2  , for 0.55 w/c ratio

The forth sample with 0.6 w/c ratio :-

NO.CUBE	LOAD (KN)	COMP.STRENGTH        (MPa)_____	STRESS  WITH (kg/cm^2)	Weight (g)
1	10	4	40.774	285
2	34.486	13.794	140.615	275

- Ave .comp- stress=  40.774+140.615  / 2  =  90.6945  kg/cm^2  , for 0.6 w/c ratio.

and this picture from excel ratio average comp-stress and w/c ratio .

COMMENTS

1) The comp-strength of sample 0.5 w/c is bigger than strength of 0.45 w/c

2) the value of comp-strength 0.6 w/c is the least of every samples strength.

3) the cement used is portland cement .

4) when increase in w/c ratio m the comp-strength decrease.

5) two sample for one w/c ratio is not enough to judge comp-strength.