Three Lab Reports

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Contents

Oedometer Test 2

Background 2

Purpose of Experiment 2

Materials and Equipment 3

Experiment Set-Up 3

A Picture Oedometer Apparatus 4

Description and Steps for Testing 4

Results Analysis Criteria 6

Determination of the Volume of the Solids 6

Determination Height of Soils 7

Numerical Examples 7

Compression Index 7

Coefficient of Consolidation 8

Conclusion 8

References 9

Experiment 1: Oedometer Test Report

Purpose

The purpose of this oedometer test experiment is to establish the rate and magnitude of volume decrease that a laterally confined soil undergoes when it is subjected to various vertical pressures. The experiment also seeks to utilize obtained data to compute the pre-consolidated pressure and coefficient of volume change.

Materials and Equipment

• Oedometer
• Oven
• Stopwatch
• Collar and mould
• Weighing and mixing pans
• Drop hammer
• Electronic balance
• Metal straightedge
• Trimming knife
• Metal scale
• Filter papers

Experiment Set-Up

A Picture Oedometer Apparatus

Description and Steps for Testing

The procedure and steps of undertaking the oedometer test were as outlined below.

1. The first step was weighing 1000 grams of soil for conducting the permeability test. Of the 1000 grams, 500g grams were sand, and another 500grams was laterite. The water added to the sample constituted 12% of the sample or 120 ml.
2. The sand and laterite soils were mixed in the pan, followed by preparation of drop hammer and mould for compaction.

• After a series of mixing, the soil sample obtained was transferred using a loading cap to the mould in three layers.

1. After transferring a sample to three layers, compaction began. During compaction of the soil, every layer attracted 15 blows of a drop hammer.
2. After compaction, the collar of the mould was removed carefully so as to avoid disturbances of soil surface. The trimming knife was additionally utilized to level the soil surface. After the leveling of the surface, the base plate of mould was removed.
3. The ring was inserted into compacted soil until it fully submerged.

• After filling, the ring with soil was removed, and the soil trimmed to suit the dimension of the ring.
• The resultant specimen was placed in an oedometer and saturated for 24 hours, followed by the application of various loads.

1. The reading of dial gauge values was recorded for different loads applied with 24 hours.

Results Analysis Criteria

Oedometer test results include the following soil properties;

1. Pre-consolidated Pressure– this refers to the optimal effectiveness sustained by the soil specimen in its geological history.
2. Compression Index-this is index-linked with the compressibility of soil. The compression index is measured as a slope of the curve between effective stress and void ratio. The effectiveness scale in algorithmic scale and the void ratio plotted on a normal scale.

• Recompression index– is derived utilizing slope or rebound –recompression curve and is utilized to derive the compressibility of over-consolidated soil.  The recompression index for most organic soils is between 0.1 and 0.2 the compression index.

Determination of the Volume of the Solids

Height of sample at the end of test (h₁)= 1.399cm and the cross-section area of the sample (A_r)=  3.142(7.5)²/4 = 44.18cm².

Volume total = h₁A_r = 61.81cm^2.

However, the soils are fully saturated, and thus.

The volume of water final= Volume of water Initial= Mass of water= 26.98 cm³.

The Volume total (Vt) = Volume of voids final (V_vf) + Volume of solids (V_s).

V_s= 34.84 cm^3.

Final void ratio (e_f) thus = V_vf/V_s = 26.96/ 34.82= 0.775

Determination Height of Soils

Height of Soils (H_s) = Volume of solids (V_s)/ Cross-sectional area (A_r) = 34.84cm³/44.18 cm²= 0.78 cm.

Changes in void final e=last dial gauge reading – first dial gauge reading multiplied by cor.factor.

H= initial height +dh

H= 1.8 + 0.05 = 1.805.

Changes in dial gauge reading d_e= dh/Hs= 0.005/0.78= 0.006

E= e_o+ d_e= 1.28 + 0.006 = 1.288

Mass volume M_v=1/ 1+ e (e₀– e₁/ σ₁– σ₀)

M_v= 1/1+1.288(1.288-0.910/196-0)= 0.76cm

Numerical Examples

Compression Index

The compression index C_c is often derived from changes in the void ratio over the effectiveness of stress correlation (Scarcella et al., 2017).

That is C_c= Δe / Δlog (σ’)

The C_c has no units and ranges from 0.1 to 10. For example, in sandy soils, the consolidated index is ranging from 0.01 to 0.06, silts soils range from 0.16 to 0.24, and for consolidated clay, it ranges from 0.20 to 0.50.

Coefficient of Consolidation

The coefficient of consolidation C_v= is a parameter showing how consolidation evolved during soil testing. Typical coefficient of consolidation values for organic clays and silt ranges from 1-10 cm; for silt clay, it ranges from 8-11 cm, and for blue clay, it ranges from 1.6 to 26 cm²/ sec. The coefficient of consolidation can be estimated from the time-settlement curve utilizing graphical methods.  The most commonly used methods are Taylor square root of time fitting method and Casagrande Logarithm of Time Fitting Method (Riad & Zhang, 2020).

Example

For 196 KPa, the calculation of coefficient of consolidation is as follows

C_V= 0.84 (H drain)²/t₉= 0.84* 0.76cm²/ 1.2 ^2 = 0.337 cm/min

Thus C_v= 5.62 x 10^-3cm/s.

Experiment 2: Sand Cone Test Report

Purpose

The purpose of this experiment was to establish base or soil material density to ascertain; it meets the project specifications.

Materials and Equipment

• Baseplate
• Weighing machine or scale
• Sand Cone or Metal Funnel
• Sand container
• Spoons, hammers, and chisels
• Oven

Sand Cone Test experimental set up

Description and Steps

1. Fill the container with sand whose density is known and weigh sand container equipment with the container filled with the sand. Label it Weight 1 (W1).
2. Measure the weight of the sand required to fill the cone. Label it W2.

• Excavate a small part of the soil and determine its weight. Label it, W3.

1. Establish the water content of the excavated soil. Label it, W.
2. Refill the excavated hole with standard sand by inserting the sand cone equipment through the opening and the hole.
3. Establish the sand cone equipment weight with the remaining sand in the container. Label it W4.

• Calculate soil’s unit of weight using the following format
• Weight of sand to fill hole= Ws= W₁-(W₂+ W₄).

Dry Soil Weight =W_d= W₃/ 1+_w

Dry unit volume = Y_d= W_d/ v

Results Analysis Criteria

1. Establish the weight of the mold (W1).
2. Measure the weight of the cone with compacted soil (W2)

• Establish the weight of compacted soils by subtracting W2-W1.

1. Establish the moist unit weight, Y = (W2-W1) multiplied by the gravity.
2. Establish the moisture can weight (W3).
3. Establish the weight of moist can with moist soils (W4).

• Establish the mass of dry soils plus moisture can (W5).
• Determine compaction moisture content (W5-W3).

1. Calculate the average moisture content and dry unit weight.

Numerical Example

Because Y_d maximum (KN/m3) = 16. 80 KN/m3

Optimum w (%)= 21. 06%

Y_d therefore is

Y_d–field= (0.95)(16.80)=16.04KN/m3

Experiment 3: Constant Head Test Report

Purpose

The objective of this experiment is to establish a sand soil coefficient of permeability.

Materials and Equipment

• Constant head permeameter
• Sand
• Graduated cylinder
• Stopwatch
• Rubber tubing
• Distilled water
• Balance

Constant head permeates experimental set u.

Description and Steps

1. Before assembling permeameter, determine the mass of two rubber stoppers, porous stones, and plastic specimen tubes.
2. Input sand in the specimen tube and create small layers of compaction by placing the porous rock about three-quarters the height of the specimen tube.

• Weigh and calculate the masses of permeameter assemblages.

1. Input the water to the specimen via rubber tubing while adjusting the water supply to ensure the level remain the same.
2. Measure and record the flow rate of water from the graduated cylinder.
3. A record flow rate of water flowing from the cylinder for a second and third time, then take the average.

• Change the head differences and repeat the same steps for ten times.

Results Analysis Criteria

Constant Head Test Data

Average k = 0.199+ 0.118+ 0.199/3= 0.117 cm/s

Data for Void Ratio

Numerical Examples

Dry Density = (Mass 2– mass 1)/ (3.142/4 *D2 * L) = (3232-2629)/(3.142/ 4 *6.35*10 cm= 1.902g/cm3.

Void ration = Gx Pw/ Pd -1 = 2.66g/cm3/ 1.873cm3-1= 0.4220

Hydraulic conductivity, k= QL/ changes in ht= 366*10 / 31.68 *60*47 = 0.118 cm/s

References

Ganju, E., Han, F., Castro, A., Prezzi, M., & Salgado, R. (2020, February). Experimental Study of Crushing in Cone Penetration Test in Silica Sand. In Geo-Congress 2020: Modeling, Geomaterials, and Site Characterization (pp. 132-141). Reston, VA: American Society of Civil Engineers.

Riad, B., & Zhang, X. (2020). Analysis of the Oedometer Test Results Using a New Method. In Geo-Congress 2020: Modeling, Geomaterials, and Site Characterization (pp. 321-331). Reston, VA: American Society of Civil Engineers.

Scarcella, G. E., Giusti, I., Giusti, S., & Lo Presti, D. (2017). Laboratory testing on compacted, partially saturated silty and sandy soils. Russian Journal of Construction Science and Technology. 2017. Vol. 3.№ 2, 3(2), 13-27.