clustering similar lines (on chart)

Firstly sorry if this is the wrong forum for this question.

I have a matrix made up of distances in meters and for every distance I have an R2 value, the chart I plot in excel is a simple line chart that shows a bunch of lines that could 'seem' to be clustered and have a relationship as the distance increases.

Now, I want to go beyond the 'descriptive' and use a statistical method that would tell me something about the relationships between the lines. This is so that I can identify 'clusters' that would allow me to group the data. I've tried K Means but this doesn't work due to asking me to categorize end allows for nodes at the periphery of the Mean figures not to be considered as part of a particular cluster. I've tried Integration and Measuring the area under the curve but this tells me a similar thing as the descriptive method.

does anyone have any bright ideas?