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Mission: Keep man-made slopes & retaining walls safe (I)

Keeping man-made slopes and retaining walls in good condition is essential. Even if they are designed and constructed to acceptable standards, without routine maintenance, their condition will deteriorate over time.  Introduction of proper “treatment” can prevent them from deterioration and collapse which may cause injury to persons or damage to your property, thus saving you a big fortune to make the slope safe, to repair your property and to compensate those injured.

How can we tell if the slopes and retaining walls have received proper “treatment”, i.e. routine maintenance? Below are some examples:

Vegetated Surface                    Shotcreted Surface

good vegetated surface    bad vegetated surface            good shotcreted surface    bad shotcreted surface

Chunam Surface                        Stone-pitched Surface vs Masonry Facing

good chunam surface    bad chunam surface            stone-pitched surface    masonry facing

Surface Drainage Measures

good surface drainage measures

bad surface drainage measures

There are so many slopes and retaining walls in Hong Kong, how can we collaborate to ensure their safety? Government departments are responsible for maintaining government slopes. For example, road-side slopes are maintained by the Highways Department, while those in public housing estates, etc., are maintained by the Housing Department. The responsibility of private owners is as conferred by the lease documents issued by the Lands Department. If in doubt, you may wish to seek advice from lawyers or estate surveyors. If an owners’ corporation has been set up for your building, maintenance of the slopes should be coordinated by the corporation.

 

Basing maintenance work on inspection results
inspection & maintenance works
Is it necessary to repair the slopes/retaining walls? How should we repair them? It all depends on the results of Routine Maintenance Inspections. The main points of Routine Maintenance Inspections for slopes and retaining walls are as follows:

 

Routine Maintenance Inspections
routine maintenance inspections                                                         
1.    Frequency: at least once a year
2.    Time-frame: inspections preferably to be conducted between October and February, and any required maintenance works to be completed before the onset of the wet season in April
3.    Inspection personnel: as professional geotechnical knowledge is not a must, inspections can be carried out by any responsible person, including property management staff or maintenance staff
4.    Inspection areas: man-made items on slopes or retaining walls + buried water-carrying services (e.g. water supply mains, sewers, stormwater drains, etc.) on or adjacent to soil slopes or retaining walls → “11+1 Actions”

 

“11+1 Actions”

Action 1: clearance of accumulated debris from drainage channels and slope surfaceAction 2:repair of cracked or damaged drainage channels or pavement
Action 3: repair or replacement of cracked or damaged slope surface coverAction 4:unblocking of weepholes and outlet drainpipes
Action 5: removal of any vegetation causing severe cracking of slope surface cover and drainage channelsAction 6:re-grassing of bare soil slope surface areas
Action 7: repair of missing or deteriorated pointing in masonry wallsAction 8:removal of loose rock debris and undesirable vegetation from rock slopes or around boulders
Action 9: repair of leaky exposed water-carrying servicesAction 10:repair or replacement of rusted steel slope furniture
Action 11: maintenance of landscape items on the slope 
+1 Action: regular check of buried water-carrying services on or adjacent to soil slopes and retaining walls

 

Abnormal features

During Routine Maintenance Inspections, if anything considered to be unusual or abnormal, such as those shown below, is found, you should report promptly to the owner or the party responsible for maintaining the land, so that a professionally-qualified geotechnical engineer can be appointed without delay to undertake necessary actions.

abnormal features

 

Completing routine maintenance inspections is only half the work done! What’s next? Please read “Mission: Keep man-made slopes and retaining walls safe (II)

For more details: Hong Kong Slope Safety website

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Last update: 2 Sep 2019
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