Detecting particles in image using morphology

Hi,

I need assistance in detecting all overlapping particles from a soil image using imerode and then calculate the diameter of each particles. Attached is sample image to do the erosion method.This is the code I have tried so far :-

    bw = imread('1.Left Upper.tif');
    figure;
    imshow(bw);

    bw = rgb2gray(bw);
    figure;
    imshow(bw);

    se = strel('disk',6,0);
    i2 = imopen(bw,se);
    figure;
    imshow(i2,[]);

     i3 =(i2>80);
    figure;
    imshow(i3);

    cc = bwconncomp(i3,8);
    n= cc.NumObjects;

But I am still unable to detect smaller particles. Please help. Thank you.