Experimental mechanism
Given that subsidence sinkholes develop from the erosion,
transport and failure of the soils that overlie cavernous
bedrock, the principal processes can be illustrated as shown
in Fig. 1. The processes have four steps. Firstly, water
percolates into soil. Secondly, particles are washed out by
percolating water to form sinkholes. Thirdly, sinkholes
enlarge. Finally, sinkholes collapse or subside downwards.
The downward transport of the cover material through
corrosionally enlarged pipes may produce two main types
of sinkholes, depending on the rheological behavior of the
mantling deposits (Williams 2003; Beck 2004; Waltham
et al. 2005).
Water seepage driven by pore water pressure proceeds
from regions of high pressure to regions of low pressure. In
the process of seeping transmission pore spaces expand,
burst, and particles lose cohesion, leading to soil failure
once the differential pressure of adjacent pores exceeds the
interparticle force. The soil failure caused by water seepage
is described by three steps (Fig. 2a), pore space expansion
(Fig. 2b), the loss of soil structure/cohesion leading to
failure (Fig. 2a).
Extrusion and tension rupture are considered to be the
main forces that destroy the soil structure. If P[f, and it
acts in the direction of long axis of the particles, it is called
extrusion (Fig. 2c), where P1 is water seeping pressure, P0
is original pressure of pores, and P (P = P1-P0) is differential
pressure at the incipient seeping stage. If P acts in
the short axis direction, it is called tension rupture
(Fig. 2d). Soils of inherently weak interparticle forces
located around the cavity fail relatively easily by extrusion,
while at the margins soil is easily ruptured under tension.
Water seeping into pores can also transport particles
with it into the pore spaces, resulting in soil aggregate
rifting, which can result in soil failure. When water pressure
overcomes the force of soil particles (including frictional
forces, molecular attraction and electrostatic forces),
(a)
Experimental mechanismGiven that subsidence sinkholes develop from the erosion,transport and failure of the soils that overlie cavernousbedrock, the principal processes can be illustrated as shownin Fig. 1. The processes have four steps. Firstly, waterpercolates into soil. Secondly, particles are washed out bypercolating water to form sinkholes. Thirdly, sinkholesenlarge. Finally, sinkholes collapse or subside downwards.The downward transport of the cover material throughcorrosionally enlarged pipes may produce two main typesof sinkholes, depending on the rheological behavior of themantling deposits (Williams 2003; Beck 2004; Walthamet al. 2005).Water seepage driven by pore water pressure proceedsfrom regions of high pressure to regions of low pressure. Inthe process of seeping transmission pore spaces expand,burst, and particles lose cohesion, leading to soil failureonce the differential pressure of adjacent pores exceeds theinterparticle force. The soil failure caused by water seepageis described by three steps (Fig. 2a), pore space expansion(Fig. 2b), the loss of soil structure/cohesion leading tofailure (Fig. 2a).Extrusion and tension rupture are considered to be themain forces that destroy the soil structure. If P[f, and itacts in the direction of long axis of the particles, it is calledextrusion (Fig. 2c), where P1 is water seeping pressure, P0is original pressure of pores, and P (P = P1-P0) is differentialความดันที่ขั้นตอนแรกเริ่ม seeping ถ้า P ทำหน้าที่ในทิศทางแกนสั้น จะเรียกว่าความตึงเครียดแตก(รูปที่ 2d) ดินของกองกำลัง interparticle อ่อนแอเสมอบริเวณไม่โพรงค่อนข้างง่าย โดยการอัดขึ้นรูปในขณะที่ขอบ ดินได้ขนาดภายใต้ความตึงเครียดน้ำดีรูขุมขนสามารถขนส่งอนุภาคมีลงในช่องว่างรูขุมขน ในดินรวมrifting ซึ่งอาจทำให้ความล้มเหลวของดิน เมื่อแรงดันน้ำovercomes แรงของอนุภาคดิน (รวมถึงการเสียดทานกอง ดึงดูดโมเลกุล และแรงไฟฟ้าสถิต),(ก)
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