An analytical study of the hazards of geological problems in engineering geological investigation

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Permeability statistics of rock mass near the cave body

Stratigraphic age	Lithology	Degree of weathering	Hole number	Hole bottom buried depth/m	Depth of test section/m	Permeability coefficient /(cm·s-1)	Water permeability q/Lu	Average value/Lu	Water permeability
P2β	Basalt	Strong weathering	ZK15	15.1	0~10	3.21×10-4		2.03×10-4	Medium permeability
					10~20	1.25×10-4
					20~30	1.64×10-4
		Mild weathering	ZKB02	59.2	40~50		2.51	1.43	Weakly permeable
					50~60		0.94		Slightly permeable
					60~70		2.85		Weakly permeable
P1q+m	Limestone	Mild weathering	ZKB02	82.6	70~80		q>120	q>100	Extremely permeable
					80~90		0.15	0.15	Slightly permeable
					90~100		q>120	q>100	Extremely permeable

Results of water permeability of rock mass (Class a) containing soluble salt

Lithologic association		Rock permeability (Lu) and number of statistical groups (sections)
Name	Designation	Strong weathering	Statistical group number	Mild weathering	Statistical group number	Fresh	Statistical group number
Sandstone group	1	62.5	8	41	15	19.8	59
Sand-mudstone interbedded class	2	28.9	15	28.9	22	21	150
Argillaceous rock with sandstone	3	37	19	61	1	10.4	28
Argillaceous rocks	4	48.0	74	38	290	9.5	1034

Corrosion of soil along the pipeline to steel structure

Hole number	Soil layer category	Depth of measuring point/m	Corrosion grade	Apparent resistivity /Ω·m
ZKY35	Muck	4	Strong corrosion	4.8
		5	Strong corrosion	3.1
		6	Strong corrosion	2.1
		7	Strong corrosion	1.9
		8	Strong corrosion	2.1
ZKB15	Silty clay	4	microcorrosion	293
		6	microcorrosion	226
	Sandy silty clay	8	microcorrosion	239

Test results of groundwater corrosion to different structures in the site

Water sampling collection point	Type of material	Steel structure	Steel bars in reinforced concrete	Concrete
				Sulfate type	Magnesium ionic type	Bicarbonate type	Carbonic type	General acid type
	Test index	Cl-1+SO42-content mg·L-1	Cl-1 content after conversion mg·L-1	SO42- content mg·L-1	Mg2+ content mg·L-1	HCO3-content mmol·L-1	Aggressive CO2 content mg·L-1	pH value
Point A	Measured value	42	13	20	1	0.69	18	6.3
	Corrosion degree	Mild corrosion	Non-corrosive	Non-corrosive	Non-corrosive	Moderate corrosion	Mild corrosion	Mild corrosion
Point B	Measured value	40	14	21	2	0.48	5	6.2
	Corrosion degree	Mild corrosion	Non-corrosive	Non-corrosive	Non-corrosive	Moderate corrosion	Non-corrosive	Mild corrosion
Point C	Measured value	36	19	24	3	0.55	14	6.5
	Corrosion degree	Mild corrosion	Non-corrosive	Non-corrosive	Non-corrosive	Moderate corrosion	Mild corrosion	Mild corrosion

Distribution of geophysical anomalies

ID	Position	Burial depth(m)	Anomalous body height(m)	Anomalous body type
1	L1-19-L1-22	6.9	1.5	Joint fissure and dissolution development area
	L2-25-L2-28	5.7	1.5
2	L3-10-L3-12	5.6	1.4	Joint fissure and dissolution development area
	L4-10-L4-12	6.1	0.5
	L5-10-L512	5.4	1.6
3	L5-16-L5-17	5.2	2.9	Joint fissure and dissolution development area
	L6-16-L6-17	11.3	1.8
4	L9-25-L9-30	5.8	3.2	Joint fissure and dissolution development area
	L10-27-L10-29	5.6	3.5
	L11-28-L11-30	7.1	3.4
5	L7-11-L7-15	6.6	6.7	Joint fissure and dissolution development area
	L8-23-L8-30	5.3	3.3
	L9-21-L9-26	6.9	7.5
	L10-22-L10-36	6.0	7.2
	L11-21-L11-26	6.1	5.4

Results of water permeability of common rock mass (Class b)

Lithologic association		Rock permeability (Lu) and number of statistical groups (sections)
Name	Designation	Strong weathering	Statistical group number	Mild weathering	Statistical group number	Fresh	Statistical group number
Sandstone group	1	32.6	41	21.8	93	5.35	237
Sand-mudstone interbedded class	2	30.8	62	18.3	86	6.01	513
Argillaceous rock with sandstone	3	21	17	28	5	3.18	28
Argillaceous rocks	4	29.4	74	19.4	321	3.91	1369