Thủy Lực Và Cơ Học Đất: Soil Mechanics Experiment Report

largest soil particles 3/8”: 1000g largest soil particles 1/2”: 3kg largest soil particles 3/4”: 5kg largest soil particles 1”: 10kg -After the end of the dry sieve, taking m g of land a

SOIL MECHANICS EXPERIMENT REPORT

Instructor: Dr Đỗ Thanh Hải

Ms Tô Lê Hương Students: All members of class VP13XDC

Ho Chi Minh city University of technology

Programme de Formation d’Ingénieurs d’Excellence au Vietnam

Contents

Experiment 1……… Page 1 Experiment 2……… Page 6 Experiment 3……… Page 12 Experiment 4……… Page 17 Experiment 5……… Page 22

-Laboratory analysis of particle size (grain size):determine the relative proportion as

a percentage of the different groups in the soil particles

-Based On grain composition and graded roads to assess the level of uniformity and gradation;waterproof permanence; select building materials; predict the mechanical properties change determines the magnitude group of particle size; the distribution and soil classification

II Laboratory instrument:

1 Using the sieve method (d >0.074mm)

-Sieve ministry: sieve cap, sieve, sieve bottoms

-Scales (accuracy 1g for large scales; 0,1g for small scales)

Dry

Sieve

Sieve size / Number

-Divided land instruments, spoon,pestle, oven (105oC), sifting machines …

2 Using the method of deposition (d <0.074mm)

-Hydrometer: used to measure the proportion of the solution

-Two cylinder:

+Cylinder 1 specimen + water (1l)

+Cylinder 2 Water used to wash hydrometer

-Stirrer, stirring rods

-Thermometer: used to measure temperature changes to correct the experimental results when the temperature changes Mixed viscosity changes velocity change calibrate -Stopwatch, bowl containingspecimen, rubber vase, Na4P2O7, sieve N10

largest soil particles 3/8”: 1000g

largest soil particles 1/2”: 3kg

largest soil particles 3/4”: 5kg

largest soil particles 1”: 10kg

-After the end of the dry sieve, taking m (g) of land at the bottom of the sieve through the sieve No.200 lavage until water no longer beads through a sieve No.200 land Part of the land

is located on the No.200 sieve (No.20, No.40, No.80, No.100, No.140, No.200) The land No.200 pass through the sieve washed in water to be condensed 1000ml also to perform deposition experiments

-Land cumulative balance (balance volume of soil from large sieve, sieve followed by small incremental weight), concentration loss <1%

2 Using the method of deposition (d < 0.074mm)

-The soil and water through a sieve No.200 will be condensed and 1000ml also entered cylinder to perform deposition experiments Swab sight each solution suspensions (soil + water) in the cylinder, then drop hydrometer into and read some reading on the hydrometer at the time of 15 '', 30 ', 45', 1 ', 2' , 4 ', 8', 15 ', 30'

-Based on the distribution characteristics of soil particles in an aqueous solution to determine the grain composition

-When the soil is made up of suspension, the average particle diameter will be about various different; Large particles will sink faster than smaller particles

-Deposition method is a method based on the proportion of the Stokes law for welding velocity

of spherical objects dropped in a liquid, depending on the particle diameter, particle density, density and viscosity of the solution of solution

IV Results of the experiment :

Total amount A = 1000g

The number

Accumulate retained amount (g)

% Retained amount

% permeable amount

Amount of drainage sieve soil B = 50g

The

number

of sieve

Size of sieve (mm)

Accumulate retained amount(g)

% Retained amount for B

% permeable amount for B

% permeable amount for all experimental model

5

 Data tables of decantation test:

T (oC)

Calib

c

Corect Indicate

d value

Rc

precipitable length

Hr (cm)

Diameter (mm)

% finer amount (P)

% finer amount for all experimental model

0.01 0.1

1 10

100

3 s

s s

Experiment 2: ATTERBERD LIMITS EXPERIMENT

I Purpose:

Define Atterberd is determined the plastic limit and the limit semis ; that is to determine the value of the moisture in the paste and plastic limit, which determines the status and name of the sticky soil

𝑤𝑃: plastic limit moisture

𝑤𝐿: limited moisture flowing

- determine the plasticity index, IP: IP = WL – WP

=> type of soil: clay, sandy clay, sandy clay soil

The name of

- determine liquid indicators, IL :(viscosity B) IL=(W-Wp)/IP

=> The State of the land: malleable plastic sticky liquid, liquid,

7

II Laboratory instruments:

(For experimental pastes limit)

+ Instruments Casagrande (lifting height cap

demand is 1 cm)

+ Trench cutter

+ The mixing knife, mixing glasses, spoon, sieve

N40 (register 0, 42 mm grains), water, cans of

sample containers, weight (precision 0, 1 g),

drying

III Sequencing experiments:

A) Liquid Limit test :

- Use about 100 g ground through a sieve to N40, mix with enough water

- Use the cutting knife, divide the land in the globe calotte into 2 equal portions (distance 2mm gap, thickness 8mm)

- Get the globe calotte lifted and fell to hr = 1 cm, velocity v = 2 times/s, count the times of the fall( N)until the ground in 2 parts of the globe calotte closed

9

- Get the loosened soil in the globe calotte, put in cans, scales, provides dried samples (24h), weight dry soil samples; determine humidity, obtained 1 pair (number per rotation, humidity)

- Taking the soil from the globe calotte out, mix well to evaporate, doing the experiment again

- Doing the same experiment about 3-4 times, determine times of the fall N 𝑖−1 < 25

< 𝑁𝑖

B) Experiment soil plastic limit:

- Taking the rest of soil of the Liquid mimit test, mix well, let the steam off loading

- Then roll them into stick (use 4 fingertips to roll) When the sticks d = 3mm and star cracking then weigh, then dry to determine humidity (If d > 3mm, cracked then add water,

If not, fold then roll)

- Doing the experiment twice in the same time and take the medium, approximation < 2%

IV RESULTS OF EXPERIMENT

Exercise 3: COMPACTION TEST OF SOIL

I Objective :

 For construction of highways, airports, and other structures, it is often necessary to compact soil to improve its strength

 Objective of Standard Compaction test :

 To determine relation between water content and dry density of soil

 To determine optimum water content and corresponding maximum dry density for soil

 To determine relation between penetration resistance and water content for compacted soil

 Importance of Standard Compaction test

 Compaction increases the shear strength of the soil

 Compaction reduces the voids ratio making it more difficult for water to flow through soil This is important if the soil is being used to retain water such as would be

required for an earth dam

 Compaction can prevent the build up of large water pressures that cause soil to liquefy during earthquakes

II Equipments

 Drying oven

 Weighing balance, accuracy 0,01g

 Standard Proctor Compaction Mold, V = 944cm3

 Standard Proctor Hammer (the height of fall is h = 30,48cm ; Q = 2,5kg)

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III Procedure

1 Obtain about 3 kg of air-dried soil and break the soil lumps

2 Sieve the soil through a N4 sieve Collect all the soil specimen passing N4 sieve in a large pan

3 Add water to the soil specimen and mix thoroughly

 Determine the quantity of water added:

1 + 0.01𝑤𝑡(𝑤𝑠 − 𝑤𝑡)

ws: the moisture contend required (%)

wt: the moisture of soil before adding water (%) m: the weight of soil before adding water ( dry soil) (ws – wt): the increase of the moisture (about 2-3%)

4 Determine the weight of the Proctor Mold + base plate (not extension) Weigh it to the nearest 1 gram

5 Attach the extension to the top of the mold

6 Pour the moist soil in three equal layers Compact each layer uniformly with the

hammer 25 times before each additional layer of loose soil is poured At the end of

the three-layer compaction, the soil should extend slightly above the top of the rim of the compaction mold

7 Remove the extension carefully Then, trim excess soil with a straight edge

8 Determine the weight of the Proctor Mold + base plate + compacted moist soil

9 Remove the base plate from the mold Extrude the compacted moist soil cylinder

using a jack

10 Take a moisture can and determine its mass

11 From the moist soil extruded in step 9, collect a moist sample in a moisture can

(step 10) and determine the mass of moist soil + can

12 Place the moisture can with soil in the oven to dry to a constant weight

13 Break the rest of the soil cylinder by hand and mix with leftover moist soil Add more water and mix thoroughly

14 Repeat steps 6-12 In this process, the weight of the mold + base plate + moist soil will first increase with the increase in moisture content and then decrease Continue the test until at least one successive decreased readings are obtained

15 The next day, determine the mass of the moisture cans + soil samples (from step 12)

A- mass of moisture can

+ moist soil g 156.055 140.783 207.177 128.761 149.637 B- mass of moisture can

+ dry soil g 146.357 129.107 185.334 112.638 127.510 C-Mass of can g 3.112 3.102 3.142 3.043 3.090

Compaction moisture

Dry unit weight, γd g/cm3 1.69 1.72 1.77 1.75 1.69

 Moist unit weight: γ = 𝐴−𝐵

𝑉

with : A- Mass of mold, compacted soil and base plate

B- Mass of mould and base

V- Volume of mold

 Compaction moisture content: w = 𝐴−𝐵

𝐵−𝐶× 100%

with : C- Mass of can

 Dry unit weight: γd = γ

1+0.01𝑤

 Results:

Maximum dry density (from plot): γdmax ≈ 1.77(g/cm3)

Optimum water content (from plot): Wopt ≈ 12 %

Compaction moisture content w (%)

B b

A m

A, B, C are coefficients dependent on c, φ

Aside from c, φ can identify with the other experiments:

+ Unconfined compression test : applied to the soil sticky, simple, direct result, the destruction would be the weakest

+ Direct shear test : applies to soil and land left stick, simple, direct result, the destruction

is between 2 horizontal surface of the cutting board cutting boxes are fixed in advance + Compression Triaxial test shall apply to all types of soil, but complex experiments to complete the targets, with 3 experimental methods; Undrained - Unconsolidated (UU), Undrained - Consolidated (CU), Drained - Consolidated (CD)

II Laboratory instruments:

Direct shear box apparatus

Round knife to create experimental soil

samples: diameter 6,3cm (A = 31.17 cm2),

height 2cm -

Gauges horizontal displacement, gauges

horizontal strain; 2 / 1000mm: 1 bar = 0,01

mm - gauges horizontal displacement

Knife, water bottle, weights to apply

pressure or undisturbed soil sample was

prepared

III Process of experiment

Firstly, soak the two samples of stone into a water container until they’re saturated

Use a steel rope to cut the cylinder-shape soil sample that is approximately 3 cm high Create a experiment sample by pressing down the round knife and whittling around the sample Then, whet the surface moothly

Cover 2 sides of sample with 2 pieces of wet-filter paper

Let the machine cut within velocity of 3mm/min until the sample is destroyed completely, record the maximum values of shearing stress

Perform the data on chart, we have the graph below:

 Prolong the line, it meets vertical exis at C=15.759 kPa is cohension force and the slope of line is angle of internal friction ϕ=34.290

Discussion:

 We can measure shear resistance of a specific soil thanks to the test

 Graph drawn is linear and similar to theory leant

Eperiment 5: Consolidation Compression Test

I Objective

Consolidation compression tests are used for determining several parameters, such as subsidence compression coefficient a, coefficient of volume changes mv, compression index cc, expansion index cs, coefficient of permeability k, modulus of deformation E, coefficient of consolidation cv, void ratios for each load level, etc with the purpose of calculating the deformation (subsidence) of the ground level

Land subsidence is the process of shrinking pore volume, also known as compression Under the impact of external loads, solid particles are folded, leading to the reduction of pore volume Hence, land is compressed

When the land is put under loads, water in the pores in the soil is absorbed and has

tendancy to drain out By consequence, pore water pressure tends to plunge, leading to the gradually increase of effective pressure Once the process of water drainage

completely happens, soil particles will suffer from all of the pressure of external loads The phenomenon of soil compression due to the steady water drainage from soil pores is called consolidation

II Instrument

 Consolidation compressor

 Modeling tools (sharp metal ring with 2cm height and cross-sectional area of 20cm2, trimming tool, steel wire can be used for cutting soft clay samples)

 Stopwatch, loads, scale, drying oven, etc

III Experiment steps

 Use metal ring and trimming tools for putting sample into shape

 Put sample in the compressor, right between two pieces of pumice

 Balance the lever using water

 Put loads on the lever: 0.25, 0.5, 1, 2, 4,…(kg / cm2) It might take at least 24 hours for the sample to reach its stable compression state under the pressure of loads

 Observe and record the figures on the deformation meter for each level of load after first 15 seconds until the deformation reached its stable state The times between each two records double respectively: 30s, 1m, 2m, 4m, 8m, 15m, … 1h, 24h

 After the stablization of the sample at the last load level, begin to remove loads,

 Determine compression index:

Cc = e200− e400log 400 − log 200 =

0.45512 − 0.3583log400200

= 0.0281

 Determine pre-consolidation pressure:

 From e-log p chart, choose the starting point of the curve and draw 3 lines: parallel

to the horizontal axis, tangent to the curve and the bisector of two above lines

 Extend the end of the curve e-log p to the intersection with the bisector at a point whose horizontal coordinate is the pre-consolidation pressure

 e-log p illustrated that there are 2 linear regions whose intersection is the

maximum vertical stress caused by the weight of the upper layer of soil in the past