Tugas Artikel Mekanika Tanah

8/17/2019 Tugas Artikel Mekanika Tanah

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Nama : Sora Dewi Pusvita

Kelas : 2 SIPIL 2 PAGI

NIM : 1110020013

TUGAS MEKANIKA TANA

A!TIKEL SE!TA !ANGKUMAN TENTANG

PE!MEA"ILITAS TANA



http://www.brighthub.com/engineering/civil/articles/119946.aspx

Soil Permeability

Soil permeability is a characteristic property of soil, an stuying it helps to erect better

structures, construct stable founations, an perform agricultural activities. !ermeability of soil epens

upon various factors, an important relate aspects are iscusse here.

Permeability can be efine as the ability of a porous mass to allow passage of water through the

meium. "nerstaning permeability means unerstaning the structure of the soil an how water passes

through ifferent layers. Soil, as we #now, has a layere structure, an water pressure at the surface woul

not be same at the mile portion. $etermination of permeability enables engineers an agriculturists to

stuy flui%flow characteristics through a soil mass an thus helps in improving wor#ability of the soil. &s

water is an essential ingreient for engineering an agricultural, wor# in the etermination of permeability

helps in retaining optimum water content so that best possible results are achieve in the minimum time.

'he pumping test an percolation test can be use in the fiel to provie information about the

permeability of soils. 'he pumping test is an active way to etermine permeability whereas the

percolation test is a passive way to fin out permeability of a soil sample uner consieration. 'he

percolation test can be performe easily, an it oes not cost much as well.

Determination of Permeability

Soil or any porous material has pores or vois that allow movement of air an water through it.

'hrough these vois, water travels an reaches the bottom of the porous material. (f the vois in a soil

mass are more, it will allow water to pass through easily an hence possess high permeability. )n the

other han, a tightly pac#e soil mass will have less space between its constituent particles, which will

not allow much water to pass through it an thus will have less permeability. *ase on the above logic,

gravel will have higher permeability than clay because gravel is a coarse aggregate an its constituent

materials are loosely pac#e.



'o etermine the flow of a flui through a porous meia, i.e. permeability of a porous mass,

Darcy's Law is use. $arcy+s aw is erive from the popular -avier%Sto#es euation, which basically

ma#es use of -ewton+s Secon aw to stuy flui substances. $arcy+s aw inclues using the viscosity of flui, pressure rop, an rate of ischarge. 'he formula use to etermine permeability is given below:

Q %k & 0!b%!a2 / μ.2

3igure & below will give a clear picture about the notations use in this formula. !lease clic# image to

enlarge.2

enotes ischarge, μ enotes viscosity, an k represents coefficient of permeability of the meium. 'he

negative sign in the formula signifies the flow of water from high pressure regions to low pressure

regions. $arcy+s aw is applicable only for slow an viscous flow conitions. $arcy+s aw is best suite

for etermination of seepage through auifers an grounwater flow cases with Reynold's Number less

than 15.

efer to the figure below showing the permeability coefficient for ifferent type of soils.



Factors Affecting Permeability of Soil

Stuying soil permeability is important because of the following reasons:

1. "nergroun seepage stuy is an important aspect of all the 7ivil 8ngineering wor#s because

once a founation is lai, you on+t want the soil mass holing your founation to lea# water.

. (t ais in the etermination of geostatic stresses an the effect of water pressure on earth

structures.

. (t gives a beforehan iea about settlement of a founation an volumetric changes in soil layers

when sub;ecte to fluis or water.

4. *efore constructing a structure, it is always helpful to #now the amount of water that can be

ischarge through a soil mass, an calculating permeability is the best way to #now the

ischarge uantity.

'here are numerous factors that affect the permeability of a soil mass. (mportant factors are mentione

below:

• 7hemical components of the interacting flui, if not water, an its temperature.

• !orosity of the soil mass uner consieration, soil compaction also impacts permeability of soil.

• !ermeability from particle si<e of soil grain si<e, particle shape, an egree of pac#ing of soil

mass constituents.

Permeability and Agriculture

(n agricultural terms, permeability helps in etermining the amount of water soa#e in by the

soil% whether rainfall soa#s into the groun or runs off to the nearest stream. (f the soil is not permeable

an allows water to stay on its surface, it will affect plant growth. =ater management techniues shoul

be applie to avoi water%logging of agricultural soils. 7ontrolle traffic an <ero tillage are the best ways

to reuce surface accumulation of water. (mproving water entryways an water storage techniues near

the fiel are also goo practices to reuce the effect of water%logging on crops. 7over crops have helpe

farmers an agriculturists to improve permeability of soil an reuce soil surface strength as well.



RAN!"#AN

!ermeabilitas tanah aalah #ara#teristi# tanah, berguna untu# membantu meniri#an stru#tur

yang lebih bai#, membangun ponasi yang stabil, an mela#u#an #egiatan pertanian.

!ermeabilitas apat iefinisi#an sebagai #emampuan ari suatu massa berpori untu# memung#in#an

bagian air melewati meium. !ermeabilitas berarti memahami stru#tur tanah an bagaimana air melewati

lapisan yang berbea. &ir merupa#an unsur penting untu# re#ayasa an pertanian, alam penentuan

permeabilitas apat membantu mempertahan#an #aar air optimal sehingga hasil yang mung#in terbai#

icapai alam wa#tu yang minimal.

";i pompa u;i an per#olasi apat iguna#an i lapangan untu# memberi#an informasi tentang

permeabilitas tanah. 'es pemompaan aalah cara a#tif untu# menentu#an permeabilitas seang#an tes

per#olasi aalah cara pasif untu# mengetahui permeabilitas sampel tanah i bawah pertimbangan.

Penentuan Permeabilitas

'anah memili#i pori%pori atau rongga yang memung#in#an pergera#an uara an air melalui itu. >elalui

#e#osongan ini, air ber;alan an mencapai bagian bawah berpori. ?i#a voi alam suatu massa tanah yang

lebih, itu a#an memung#in#an air untu# melewati engan muah an #arenanya memili#i permeabilitas

tinggi. $i sisi lain, massa tanah yang paat a#an memili#i sei#it ruang antara parti#el penyusunnya,

yang tia# a#an memung#in#an banya# air untu# melewati itu an engan emi#ian a#an memili#i

permeabilitas #urang. *erasar#an logi#a i atas, #eri#il a#an memili#i permeabilitas lebih tinggi ari

tanah liat #arena #eri#il aalah agregat #asar an bahan penyusunnya i#emas secara longgar.

"ntu# menentu#an aliran fluia melalui meia berpori iguna#an @u#um $arcy.

umus yang iguna#an untu# menentu#an permeabilitas:

Q $ kA%&Pb%Pa( ) *+L(



menun;u##an ebit

A menun;u##an vis#ositas

# merupa#an #oefisien permeabilitas meium

'ana negatif alam formula menana#an aliran air ari aerah berte#anan tinggi #e aerah te#anan

renah

@u#um $arcy berla#u hanya untu# #onisi aliran lambat an #ental

Permeabilitas dan Pertanian

$alam istilah pertanian, permeabilitas membantu menentu#an ;umlah air yang irenam alam tanah%

apa#ah curah hu;an membasahi #e alam tanah atau lari #e aliran tere#at. ?i#a tanah tia# permeabel an

memung#in#an air tinggal i permu#aan, itu a#an mempengaruhi pertumbuhan tanaman.

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