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Pertemuan 06<<Judul>>

Matakuliah : S0182/Studi Kasus Dalam Teknik Sipil

Tahun : Juli 2005

Versi : 01/01

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Learning Outcomes

Mahasiswa dapat membandingkan kasus-kasus yang terjadi dengan berbagai alternatif yang dipilih C4

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Outline Materi

• Analisa pemecahan masalah

• Beberapa alternatif pemecahan masalah

• Kasus kegagalan konstruksi yang mungkin terjadi

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PAVEMENT STRUCTURAL FAILURE

This is when the PAVEMENT has failed, maybe not completely, but in a major way. The PAVEMENT is no longer able to absorb and transmit the wheel loading through the fabric of the road without causing fairly rapid further deterioration of the road pavement. The layers making up the PAVEMENT have failed for various reasons, E.g. through age, inadequate design, or an altering in requirements of the strength of the PAVEMENT by increased traffic flow/weight, impeded drainage decreasing subgrade strength, etc..

When you have STRUCTURAL FAILURE the solution is always a form of RECONSTRUCTION.

I say a form of RECONSTRUCTION because it is not always necessary or even advisable to remove material that is still sound and will provide a good base to new work.

If total RECONSTRUCTION is needed so be it, but you really need the experts in here to advise,I mean real experts with a few years of real experience not just somebody with a fancy machine, however much data they can provide. SEEK GOOD ADVICE !

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DRAINAGE

• DRAINAGE is VERY! VERY! VERY! IMPORTANT, both in relation to road pavement construction and maintenance.

You MUST keep the water-table low to prevent the moisture content of the subgrade increasing, and hence decreasing the subgrade strength, measured by the CBR value, on which the road pavement was designed.If this is not done by the use of french drains, or even open ditches adjacent to the highway, the road pavement will weaken and fail.

The water-table of naturally occurring ground will rise and fall from winter to summer, bear this in mind when designing the road, and design for the highest water table (weakest subgrade) conditions. Good drainage will help to keep the water table of the road pavement in equilibrium.

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DRAINAGE

Also the road pavement itself must be constructed so that it will drain in the event of a failure of the integrity of the surfacing layers, i.e. if water is able to enter the road pavement there must be a path for it to exit.The internal drainage function of a road pavement is usually performed by the GSB layer, this itself MUST be drained in some way. In my younger days this function was provided by a french drain on the lower side channel and periodically piped to an outside drain or open ditch, but this practice seems to have become redundant.

Water below the road pavement must be kept low and not be allowed to rise up into the construction layers, (and water CAN flow upwards, by capillary action).

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DRAINAGE

• IF WATER IS ABLE TO ENTER THE ROAD PAVEMENT, FOR WHAT EVER REASON, THE DESIGN OF THE ROAD PAVEMENT SHOULD BE SUCH THAT THE WATER HAS A WAY OUT, THIS IS USUALLY THROUGH A SUB-BASE LAYER THAT IS DRAINED TO AN INSTALLED DRAINAGE SYSTEM.IF WATER CANNOT FIND A PATH OUT OUT THE ROAD PAVEMENT FAILURE OF THE HIGHWAY WILL BE PREMATURE AND SWIFT.

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FAILURE

• AREAS OF FAILUREWhen you have areas of failure in a road surface it is necessary to investigate the cause of the failure to decide the course of action to effect a permanent repair.

• Excavating a trial hole is an excellent way of finding out just what the road pavement consists of, or does not consist of, as the case may be.

• It will also indicate the nature of the failure, i.e. failure of the materials making up the road pavement, lack of construction thickness, high water table/poor drainage, etc..

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• THE BASICSIt is good practice to record all the trial hole details.

• Record the thickness of the various pavment layers, i.e. wearing course, basecourse, roadbase, sub-base.

• If you are sufficiently knowledgeable identify the various materials, e.g. hot rolled asphalt wearing course with precoats, or close graded macadam wearing course, etc..

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• If possible be on site when the trial hole is excavated and observe the procedure, it is amazing what you can learn just from using your eyes.

• How hard was it for the workman to jack hammer through the various layers.If it was easy the materials in the varying pavement layers are not that strong.If it was "hard going" through the various layers the pavement is strong, and the materials are unlikely to be the cause of any failure.

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• Even something as simple as the degree of difficulty in digging the hole will give an indication of the strength of the materials that make up its construction.

There is very little substitute for experience in trial hole assessment but some things are common sense:- 1) How thick is the construction, how thick are the various layers. 2 ) What type of material is it? bituminous, concrete, granular, what condition is it in.3) What is the height of the water table. 4) What is the type of subgrade, what is the CBR of the subgrade. 5) Is the road pavement material excavated in sound condition or stripping and loose.

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