Water Slide Report________________________________________________________

CIV1900 Civil Engineering SkillsGroup 2C

Selina RaiJames Featherstone

Nimmit ShahTin Yee Shum

Natalia GrachevaHarry Eddolls

Florence Maskell

Executive Summary

This report aims to explain the design process undertaken for The Rainbow Snake using civil and structural engineering principles and calculations. The “adventure water slide” is to be located in Rother Valley Country Park located in the south east of Sheffield and serves as an extension of the range of leisure activities, including various water sports and an adventure playground that is already available. The water slide facilities will be located in an area alongside the existing adventure playground and will be suitable for reasonably young children (aged 8 or above).

The project lasted a total of 5 days, the first 2 days in which the team conducted a site visit to undertake a series of investigations of the various aspects of the design problem. These included the following tasks:

1. Survey the proposed site of the slide, taking measurements of the elevation of the hill side and the horizontal distances

2. Undertake an experimental process to investigate and design a supporting structure to hold the water slide at a given height above the ground

3. Undertake a geo-technical survey of the local ground conditions to determine the available foundation designs

4. Undertake a series of experiments to determine the how the depth and flow velocity varies in a water slide, and by using this information to design a fun and exciting water slide.

The design of the swimming pool and water slide was then designed based on these investigations, such as the geological section derived from a levelling survey, and the estimation of water flow and velocity. Several specifications were however already predetermined prior to the project. For example, the required length of the slide is at least 75m, and the design must incorporate an exit pool. The minimum dimensions of the swimming area must be 25mx10mx1.8m deep (at the deep end). The final slide design is that it will be made of semi-transparent coloured PVC, and 120m long with an internal diameter of 1.5m. The average velocity is 1.84m/s and the average ride time was found to be 34.6 seconds.

Facilities including changing rooms, a cafe, lounging area and a First Aid station are provided onsite. A belt conveyor is also included in the conceptual design for easy access to the top of the slide, especially as it caters to younger children also.

IntroductionThe Rainbow Snake is a colourful adventure waterslide, located in Rother Valley Country Park, and designed to be fun for ages eight and upwards. The water park is set with a rainforest theme, and this is very much evident in the water slide. The rider is transported from the top of the ride through a rainbow of colours, created by light coming through the semi-transparent coloured PVC tubes, before emerging from the rainbow snake’s mouth into a rainforest outdoor pool. A pump will move the water from the pool to the top of the slide, passing through a filtration system as it is pumped to ensure it remains clean. Based at the bottom of the slide will also be several facilities such as changing rooms, a cafe and a First Aid station.

Figure 1. Conceptual design of the water park

This report aims to explain the design process undertaken for The Rainbow Snake using civil and structural engineering principles and calculations. This was done so by surveying the site, conducting ground investigations on site, design/constructing the supports and foundation for the water slide, and design/testing a physical model of the water slide.

Site InvestigationIn order to derive an interpretation of the ground conditions for the site, the team investigated three boreholes taken along the site and looked at a quarry at the northern end of the Rother Valley Country Park and at a disused quarry in Rotherham. The borehole information is assumed to be the same for the site.

The 3.5m exposed rock face of the quarry allowed the dip of the sandstone layer to be assessed. This was found to be around 87° and it was assumed the slide site would have a similar dip. This angle was then compared to the section with borehole and it was found that this fitted with the layers of sandstone between the first and second borehole, but not between the second and third. It was therefore assumed that there must be a fault between the second and third borehole. More ground works investigation would be required before construction, to determine the exact location of the fault.The thickness of the bed and rock description at each location was recorded in table x, as was the positions of the tapes on the slope and the measurement of the top and base of each bed.

The Height of Collimation method of levelling survey was used to determine the topography of the ground for the slide geometry. Adjustments were not added as the Group was not able to come down the hill to the starting point.

The pad footings are assumed to be suitable to support the slide, whereas the size and founding levels of these must be estimated. Also, rock strength and fracture spacing are estimated to design the foundations and determine the method of excavation of the swimming pool.

Physical Model TestingAs part of the design process, a support to hold the water slide was designed and tested using steel sections, tension members and ballast weights. The structural form must be considered in relation both to the slide geometry and the loads to be carried. There must be clear load paths from the loading sources to the foundations. It may be assumed that prefabricated sections of the slide channel itself can be purchased from a manufacturer complete with waterproof connections.

3. Estimation of water flow and outline design of circulation systemThe rate of water flow will depend on the slide gradient and water depth. It will thus belinked to speed of descent. Estimates of flow rate and speed of descent are required. Inorder to make these estimates, some experiments will be carried out in the field.

Water Calculations

Initially the rate of discharge was measured through a straight section of pipe at various slope gradients. Then a scaled model of the proposed slide design was constructed, this was then tested and by taking various measurements used to calculate values such as the rate of discharge and speed of the water. Furthermore, this information was then used to predict the corresponding values for the full scale slide.

For our model -

Average discharge, Q =volume collected

time =20×10−3

26=0.77×10−3

Average depth of water in pipe, d =9.7mm

Average area of flow, A=r2(σ−12sin 2σ)=4.19×10−4 where σ=0.59

Average velocity = QA

=¿1.84m/s

Measured Length of slide = 4.0mAverage measured time to slide = 4.85s

For the full scale slide-Based on a 120m slide with an internal diameter of 1.5m and a water depth in the pipe equivalent to the water depth measured in the model.

Average area of flow, A=r2(σ−12sin 2σ)=1.55×10−3 where σ=0.161

Using VmVr

=√ PmPr WhereP=2 rσ , therefore Pm=0.068and Pr=0.24

Vr=3.47m /sThen usingQ=V × A, Qr=5.37×10−3

Finally, by using Time= lengt haverage velocity The ride time was found to be 34.6 seconds.

Pump sizing and power:By using the equation Hpump=Z+ fQr2 , the total head was found to be 28.57

Then by using Powe r p=ρ⋅ g ⋅Hpump ⋅Qr

η and taking the efficiency,ηto be 85% the power required was

found to be 1.77kW. By comparing this with the average cost of electricity in the UK, it was calculated that it would cost 31p/hour.

Slide weight and loads:Based on a cylindrical tube with an external diameter of 1.53m and an internal diameter of 1.5m the cross sectional area of the tube would be 0.071m², multiplying this by the length of the slide would give a total material volume of roughly 8.502mᶾ. Through internet research, we found the density of the polymer used to be 1200kg/mᶾ, which gave a total slide weight of 10,200kg.The mass of water in the slide at any instance was calculated using the average water area of1.55×10−3, multiplied by the slide length of 120m and the density of water. This gave a water mass of 186kg. By summing the mass of water, mass of slide and mass of an average person, the total mass calculated was 10,500kg which when multiplied by gravity gave a total force of 103kN. Divided over 14 supports this would give an average load of 7.33kN per support.

Here you can see the conceptual design of the slide, with the snake theme incorporated. The structure shown is the style of roof and building which are planned to be used on the main building construction.

Materials

The SlideThe slide is formed from dozens of fiberglass reinforced plastic segments fastened together with heavy-duty bolts. Typically, the individual segments fit together like sections of a toy race track (see figure 1). The fiberglass reinforced plastic used to make the slide is relatively cheap, durable and has a very high strength to weight ratio.

Figure 1: different sections of construction and their integration

Steel SupportsThese segments rest on a framework of steel girders. The girders may be positioned directly below the slide, or they may sit adjacent to the slide, supporting it with sturdy cantilevers.

Figure2: This water slide is built around several steel columns, which hold up the fiberglass reinforced plastic segments with strong cantilever supports.

Figure 3: The pump system

This slide has a pump that is housed in a building near the base of the slide. In the standard design, the pump motor turns a drive shaft, which is attached to a propeller. The spinning propeller drives water forward, in the same way an airplane propeller moves air particles. In a typical set-up, the water line has a check valve, also called a one-way valve, positioned between the pump and the top of the slide that prevents the backflow of water.At night the water in the water park is filtered (see figure 4). As water moves up through the sand, it dislodges the bits of dirt. This backwash is pumped out to the sewer line. Also water that has been lost during the day and to cleaning can be reimbursed into the system.

The foundationsFoundations are used to transmit the load of the fiberglass reinforced plastic slide and the steel frame to the soil below. The main purposes of a foundation are:

○ To distribute the load received by the steel girders over a large area○ To load the substratum evenly so as to prevent unequal settlement○ To take the structure sufficiently deep into the ground to prevent overturning

Before deciding where the foundation was laying upon, a geological survey was undertaken to know what types of soils and rock layer existed beneath the surface and upon which soil types the foundation can be placed.

Foundation decided upon that will match the criteria above: Floating Slabs (or floating foundations) are concrete slabs with a continuous grade beam. Spread directly under a column or reinforced along the bottom, continuous grade beams carry the vertical load of the columns. The basic ingredients of concrete foundation include: Water Aggregates (sand and gravel) Portland cement and Admixtures. Admixture is used to strengthen or cure concrete as it is poured.

Pool DesignThe pool will be 25m in length and 10m in width, with an area of 250m 2. The maximum depth of the pool is 1.8m and it becomes shallower at the edges for the convenience of users (refers to figure 4). As the depth is 1.8m at the centre of the pool, customers should be able to swim.

About the construction of pool, thickness of each wall would be 1m and pumping system would be constructed for water circulation. Materials used for the exterior wall would be reinforced concrete and the interior wall would be tile. The waterproof membrane is vinyl liner which costs less and takes shorter time for construction compared to other in-ground pool types.

In terms of the excavation method, total depth needed to be excavated is 3m below the ground. While 1.8m is the depth of the pool and 1.2m is the foundation. According to the borehole record 1, stratum is medium bedded SANDSTONE which is strong and UCS of it is between 50 and 100 MPa. Moreover, fracture spacing is . From the data obtained, lengths of scan line are 13.5 and 11.5 respectively and the numbers of joints are 7m and 5m respectively. By calculation, the fracture spacing is around 2m. Therefore, blasting would be used for excavation. Total ground excavated is 27x12x3=972m3, with an area of 324m2.

Rock blasting is the controlled use of explosives and other methods such as gas pressure blasting pyrotechnics to excavate, break down or remove rock. Production Blasting would be used for excavation which large explosive charges are using. Large rock burdens would be removed but it would reduce the strength of the remaining rock and soil mass.

Figure 4: Pool Design

ConclusionThe appeal of this addition to Rother Valley Country Park is that it is something which appeals to all ages – fitting in with the currently existing water sports and activities there already. The colourful slide and fun indoor pool is fun for younger riders, whereas the twists and turns mean that it can be enjoyed by all ages, parents included. Should the parents wish to stay dry, they can sit in the cafe and watch their children play safely from behind glass panelling. The aim of this slide feature is to act as the starting point for a growing water park in Sheffield, The Rainbow Snake being the central feature, snaking down the steep hill on which it is situated.

Changes we could make include: making the slide flatter at the looping section so that the water and rider would be able to get up the slope of the loop; improving the support of the slide, ensuring it is supported both laterally and vertically; adding an automated way of taking riders to the top of the slide, as the hill itself is very long and steep, especially for younger riders; and finally expanding the rainforest theme into a water park with The Rainbow Snake as its central feature.

The design of the slide would be a large attraction to both Sheffield and to Rother Valley Country Park. If it was built, we have utmost confidence that The Rainbow Snake would fit in with the existing activities at the park, and would become the main attraction.