Impact of Frost Heaving on Catch Basin and Road Infrastructure. Presented By: Kurtis Anketell, EIT Public Works Department

Transcription

1 Impact of Frost Heaving on Catch Basin and Road Infrastructure Presented By: Kurtis Anketell, EIT Public Works Department

2 Outline Introduction Heaved Catch Basin Problem in Red Deer Frost Heave Indicators Cause of Frost Heaving Heaved Catch Basin Program Solutions Cost Future Questions 2

3 Introduction How does frost heaving affect catch basin and road infrastructure? 3

4 Introduction 4

5 Extent of Heaved Catch Basin Problem ~8000 catch basins installed ~5500 are located on paved streets ~800 (15%) have indications of heaving Priority 1 Priority 2 5

6 Frost Heave Indicators - Concrete Cracked, lifted, and/or tenting of concrete sidewalk/curb and gutter 6

7 Frost Heave Indicators - Asphalt Asphalt degradation, sinkholes, humps, and/or large cracks 7

8 Frost Heave Indicators Catch Basins Damaged, broken, and/or no longer functioning catch basins and leads 8

9 Why is Frost Heaving a Problem? Differential heaving causes damage to road and underground infrastructure, significantly reducing its useful life: Asset Useful Life (Years) Actual (Years) Concrete Sidewalk, Curb & Gutter 30 5 Asphalt Pavement Catch Basins Catch Basin Leads Damage results in increased liability for the City through: Trip hazards and potential for personal injury Road hazards and potential for property damage / personal injury Flooding in summer and ice buildup in winter Increased operational and capital costs to continually address damaged and hazardous infrastructure 9

10 What Causes Frost Heaving? Frost Heaving requires three factors: Water Frost susceptible soils Freezing temperatures Ice Lensing 1. Figure By Williamborg - Own work, Public Domain, 2. Figure from Edmonton Experience With Bottom Ash And Other Insulating Materials For Mitigation Of Frost Heave Induced Damage In Pavements, conf.tac-atc.ca/english/annualconference/tac2011/docs/sm1/field.pdf 10

11 What Causes Frost Heaving? Water: Saturation of the native sub-grade soils increases the effect of icelensing in the winter, and can be due to the following: High groundwater table Rain or meltwater Leaking catch basins and leads Frost Susceptible Soils: Typically consist of silts and clays (glaciolacustrine deposits), which are widespread throughout Alberta The characteristics of these soils allow capillary action / wicking of water upwards. This capillary action is what classifies a soil as frost susceptible 11

12 What Causes Frost Heaving? Freezing Temperatures: Water expands ~9% when frozen, causing expansive ice lensing and uplift of the overlying soils Frost depth in Red Deer is ~2 2.5 meters, and is typically deepest in March, corresponding with the greatest level of heaving Municipality Freezing Degree-Days ( C) Red Deer 1323 Calgary 995 Edmonton 1441 Grande Prairie 1648 Fort McMurray 2236 Lethbridge 737 Medicine Hat

13 Heaved Catch Basin Program (HCBP) The Heaved Catch Basin Program aims to address catch basins and catch basin manholes that are chronically heaved by minimizing the three factors of frost heaving. Eliminate source of water: Use watertight catch basin and lead materials Install sub-drains to remove water from road structure Remove frost susceptible material: Under catch basins and replace with non-frost susceptible material Under sidewalks/roads and replace with granular materials Reduce frost penetration: Install rigid insulation below catch basin and under sidewalks/roads 13

14 HCBP Timeline Recognition of CB Heaving Problem Trial solutions developed & implemented First year of HCB program Full new design of solutions 45 Catch Basins Frost Treated Iteration of 2017 designs Third year of HCB program 90 Catch Basins Frost Treated Contract Specification Changes Iteration of 2016 designs Second year of HCB program 99 Catch Basins Frost Treated 14

15 HCBP 2015 Trial Treatments

16 HCBP 2015 Trial Treatments Post-Construction Analysis of Treatments Fall / spring survey determined catch basin movement was negligible Analyzed constructability and cost of each treatment Existing catch basin infrastructure was in poor condition Key Design Considerations Replace catch basin infrastructure at each treatment site Thermal transitions for rigid insulation required Match existing backfill material Ensure road structure is installed to back of sidewalk Use materials requiring little compaction under catch basins Review City construction specifications for storm infrastructure 16

17 HCBP Construction Practices Current City Specification for Lead Installations: Connection to Catch Basins and Manholes 1. Break out opening to suit pipe diameter 2. Cut pipe to conform to inside wall of manhole or catch basin 3. Grout pipe in place 4. Encase first 0.5m of pipe in concrete Problems with this specification include: Breaking out an opening causes structural damage, reducing the lifespan of the structure Grouting fails prematurely due to poor constructability in combination with freeze/thaw cycles Concrete encasement of pipe is meant to reduce settlement failure at a structure, but it became excessive Poor specifications, inspection practices, and constructability result in the installation of poor quality infrastructure, costing municipalities in the long term. 17

18 HCBP Construction Practices 18

19 HCBP Current Materials Catch Basins Catch basins are not required to have gaskets for lead connections Use of bricks, wood, grader blades, and other non-standard methods as grade rings 19

20 HCBP Current Materials Catch Basins 20

21 HCBP Required Materials Catch Basins Catch Basins Monolithic base catch basins / catch basin manholes only Rubber gasket cast into catch basins / catch basin manholes at plant for lead connection(s) Concrete grade rings only to bring frame and grate to grade Seal all joints using bituminous asphalt or equivalent to prevent infiltration of soil particles 21

22 HCBP Current Materials Leads Common lead materials installed include: culvert, concrete, PVC The table below describes the City s experience with the performance of these pipe materials for catch basin leads only: Material Type Years Used Culvert (CSP) 1950 s 1995 Concrete 1970 s Present PVC 1995 Present Water tightness Poor Poor Good Flexibility Fair Poor Good Repairability Good Poor Good Degradation Poor Fair Good Ease of Installation Fair Poor Good Lifespan Poor Poor* Good 22

23 HCBP Required Materials Leads PVC for leads (Ribbed or SDR35) Considered flexible and can withstand frost heave forces Is watertight due to gaskets and spigot/bell system Compatible with gasketed catch basins, eliminating grouting Ribbed pipe requires use of ribbed DR35 adapter for compatibility with gasketed catch basins Low long-term maintenance costs 23

24 HCBP Solution Concrete Sidewalk, curb, and gutter Addition of fibre reinforcement to concrete to control cracking Rebar placed in gutter pan bulb where smaller pieces are prone to deterioration Additional control joints added, spaced every 750mm, the first 3 meters on either side of CB Caulking around frame and grate to reduce water infiltration 24

25 HCBP Solution Road Structure Extend granular material to back of sidewalk to prevent differential movement and longitudinal cracking Rigid Insulation Requires a taper to transition from no movement to full movement Insulation is not always the best solution. It can cause: Road and sidewalk to freeze earlier than the surrounding ground, causing early frost formation, accumulation of snow/ice, and unexpected slippery conditions Slight dip in winter at CB due to road moving and CB not Bump at transition where insulation starts and stops Insulation allows catch basins to thaw quickly in spring, reducing the need for steaming 25

26 HCBP Frost Treatment 1 Used in areas that exhibit extreme amounts of movement Designed to stop frost heaving in catch basins and provide a smooth transition from no-to-full movement in the surrounding road 26

27 HCBP Frost Treatment 2 Used in areas that exhibit moderate amounts of movement Similar to Frost Treatment 1, except less surface insulation is installed 27

28 HCBP Frost Treatment 3 Designed to stop heaving of 2 2.5m deep catch basin manholes Top insulation same as Frost Treatment 1; one layer of insulation below barrel and no rock base 28

29 HCBP Frost Treatment 4 Used to stop movement of frost-susceptible soils around deep catch basin manholes Surface insulation only, with same profile as Frost Treatments 1 & 3 29

30 HCBP Frost Treatment 5 Designed for use in areas that exhibit minor levels of heaving Replaces frost susceptible material below the catch basin, to a depth equivalent to the thickness of the road structure Recommended to be installed for all new catch basins 30

31 HCBP Frost Treatment Installation Step 1: Remove existing catch basin and excavate to required depth Applies to Treatments: 1, 2, 3, 5 31

32 HCBP Frost Treatment Installation Step 2: Place filter fabric and install rock base (400mm thick) Applies to Treatments: 1, 2, 5 32

33 HCBP Frost Treatment Installation Step 3: Place sand and insulation (100mm thick OR 50mm thick) Applies to Treatments: 1, 2, 3 33

34 HCBP Frost Treatment Installation Step 4: Install new catch basin, connect lead, and backfill Applies to Treatments: 1, 2, 3, 5 34

35 HCBP Frost Treatment Installation Step 5: Install top insulation and sand Applies to Treatments: 1, 2, 3, 4 35

36 HCBP Frost Treatment Installation Step 6: Reinstate road and sidewalk Applies to Treatments: 1, 2, 3, 4, 5 36

37 HCBP Frost Treatment Cost Cost of Heaved Catch Basin work is as follows: Frost Treatment 1, 2, & 5: ~$13,500 (new CB included) Frost Treatment 3: ~$16,000 (new 2.0 vert.m. CBMH included) Frost Treatment 4: ~$10,000 Frost Treatment 5 for a new catch basin installation: ~$750 premium Costs related to continuous repairs at heaved catch basins: Administration time for dealing with complaints, inspections, etc. Replacement of 6 meters of sidewalk, landscaping, and asphalt curb cut reinstates, every 5 years Patching, grinding to address trip hazards between full concrete replacement Filling asphalt sinkholes Repair/replacement of damaged catch basin infrastructure 37

38 Future Continue with the Heaved Catch Basin Program Update the City s Contract Specifications Reflect modern construction procedures and materials Recommend Frost Treatment 5 be installed for all new installations Include all frost treatments for widespread use in rehabilitations Educate City/Consultant personnel 38

39 Questions? 39